Consistently, more than 170,000 men and ladies in the United States bite the dust from a heart assault. Knowing this, a worldwide group of scientists united to make the Fatty Acids and Outcomes Research Consortium (FORCE), with a specific end goal to unwind reality behind how eating routine can enhance a man's odds of surviving a heart assault. Their discoveries, distributed in the JAMA Internal Medicine, discovered basic sustenances like salmon, mackerel, walnuts, pecans, and hazelnuts might be an approach to eat your way to a higher rate of survival.
"These new results, including numerous studies which beforehand had not reported their discoveries, give the most far reaching picture to-date of how omega-3s may impact coronary illness," said the study's lead creator Liana Del Gobbo, a postdoctoral examination individual at Stanford University School of Medicine, in an announcement. "Over these differing ponders, discoveries were likewise reliable by age, sex, race, nearness or nonattendance of diabetes, and utilization of ibuprofen or cholesterol-bringing down pharmaceuticals."
For the study, FORCE analysts analyzed 19 studies from 16 distinct nations around the globe, which included 45,637 members. They concentrated on every member's day by day dietary admission, alongside if and when they encountered their first heart assault and if or when it prompted a fast approaching passing. Of the 7,973 members who showed at least a bit of kindness assault, 2,781 did not survive. In the wake of computing the measure of omega-3 unsaturated fats every member expended once a day, they found the individuals who ate both plant-and fish based omega-3s had a 10 percent lower danger of encountering a deadly heart assault.
"Most earlier investigations of dietary fats have depended on self-reported evaluations of admission," said the study's senior creator Dariush Mozaffarian, the dignitary of the Friedman School of Nutrition and Policy at Tufts University, in an announcement. "This new worldwide consortium gives an exceptional chance to see how distinctive fats and unsaturated fats identify with different wellbeing results, and numerous extra examinations are in advancement."
The exploration group trusts their discoveries will have the capacity to put questions to rest about the constructive outcomes that omega-3 unsaturated fats can have on a man's heart. The general rate of lethal heart assaults in the United States could bit by bit diminish if individuals ate a more prominent measure of omega-3 fats. As indicated by Mozaffarian: "during an era when a few however not different trials of fish oil supplementation have demonstrated advantages, there is instability about cardiovascular impacts of omega-3s. Our outcomes loan backing to the significance of fish and omega-3 utilization as a component of a solid eating routine."
What is it about omega-3 fats that give a man's heart the quality to make due after an assault? While the human body can make the greater part of the distinctive sorts of fats it needs to work from crude materials, it can't do as such with omega-3 fats. As indicated by the Harvard School of Public Health, in light of the fact that the body can't make them out of scratch, a man needs to gain them from sustenance, which incorporates fish, vegetable oils, nuts, and flax seeds. Once devoured, they begin making hormones to manage blood coagulating, the contracting and unwinding of the corridor dividers, and irritation. These hormones give omega-3 fats the capacity to give the heart an enduring beat — at last lessening the danger of touching off a lethal heart assault.
Skip to content
CHECK YOUR SYMPTOMS FIND A DOCTORSIGN IN SIGN UPSUBSCRIBE
WebMD: Better data. Better wellbeing.
Wellbeing
A-Z
Regular ConditionsVIEW ALL
Include/ADHD
Hypersensitivities
Joint pain
Malignancy
Cool, Flu and Cough
Gloom
Diabetes
Eye Health
Coronary illness
Acid reflux/GERD
Torment Management
Sexual Conditions
Skin Problems
Rest Disorders
Highlighted Topics
See What Severe Psoriasis Looks Like
16 Tips to Help You Get Organized
Feeling Your Best When You Have MS
Side effect CheckerWebMD
Side effect Checker
Wellbeing Concern On Your Mind?
See what your therapeutic indications could mean, and find out about conceivable conditions.
Begin
Assets
SECOND OPINION
Perused master points of view on well known wellbeing subjects
Groups
Associate with individuals like you, and get master direction on carrying on with a sound life
Protection GUIDE
Get prepared for changes to your social insurance scope
Doctor DIRECTORY
Discover a specialist in your general vicinity
Torment Coach
WebMD Pain Coach AppTrack your agony levels, triggers, and medications. Set objectives and get tips with our application.
Download
DRUGS and
SUPPLEMENTS
Discover Information About:
Drugs and Supplements
Get data and surveys on doctor prescribed medications, over-the-counter solutions, vitamins, and supplements. Seek by name or medicinal condition.
Find or Review a Drug
Find or Review a Vitamin or Supplement
Check for Drug Interactions
Drugs Basics and Safety
Generally Abused Drugs
What's Your Medication IQ?
Taking Medications During Pregnancy
Pill IdentifierWebMD
Pill Identifier
Experiencing difficulty recognizing your pills?
Enter the shape, shading, or engraving of your solution or OTC medication. Our pill ID instrument will show pictures that you can contrast with your pill.
Begin
My MedicineWebMD
My Medicine
Save your prescription, check associations, agree to FDA cautions, make family profiles and that's just the beginning.
Begin
Drug News
Vitamin B12 May Not Help Some Seniors
Do Supplements Give Athletes an Edge?
New Schizophrenia Drug Approved
FDA: New, Stronger Warning for NSAIDs
New Drug Approved for Heart Failure
WebMD
Portable Drug Information App
WebMD Mobile Drug Information AppDrug, supplement, and vitamin data on the go.
Download
LIVING
Sound
Highlighted Content
Enhance Your Concentration
Enhance Your Concentration
These Foods and Drinks Can Help
WebMD
Hypersensitivity App
WebMD Allergy AppFight hypersensitivities with day by day conjectures, nearby alarms, and customized tips.
Download
Living Healthy CentersVIEW ALL
Diet, Food and Fitness
DIET, FOOD and FITNESS
Diet and Weight Management
Weight reduction and Obesity
Sustenance and Recipes
Wellness and Exercise
Excellence and Balance
Excellence and BALANCE
Solid Beauty
Wellbeing and Balance
Sex and Relationships
Oral Care
Living Well
LIVING WELL
Ladies' Health
Men's Health
Maturing Well
High schoolers
Fit Kids
Included Topics
Conquer Your Fear of Public Speaking
New Clues Why Mosquitos Attack You
Why Do You ... ACHOO!?
Streak Fitness: Try the 7-Minute Workout
Have Sensitive Teeth? See What to Do
16 Tips to Help You Get Organized
FAMILY and
PREGNANCY
Included Content
What's That Rash?
What's That Rash? Step by step instructions to Treat Childhood Skin Problems
WebMD
Pregnancy App
WebMD Pregnancy AppThe huge day is coming! Get sorted out and track infant's week after week advancement.
Download
Family and Pregnancy Centers
Pregnancy
PREGNANCY
Attempting to Conceive
In the first place Trimester
Second Trimester
Third Trimester
Child rearing
Child rearing
Infant and Baby
Youngsters' Health
Youngsters' Vaccines
Bringing up Fit Kids
Pets
PETS
Solid Cats
Solid Dogs
Included Topics
At the point when Autism Grows Up
Top Children's Hospitals Ranked
Antidepressants Linked to Birth Defects
At the point when Are You Contagious?
Which Birth Control Is Best for You?
New Test May Help Spot Male Infertility
NEWS and
Specialists
NewsVIEW ALL
Why You Should Rethink That Drink Before Dinner Why You Should Rethink That Drink Before Dinner
New Clues Why Mosquitoes Find You Irresistible New Clues Why Mosquitoes Find You Irresistible
ARTICLE
Ladies: Too Much Sitting Ups Cancer Risk
ARTICLE
Famous Heartburn Meds Can Have Health Risks
ARTICLE
Do Supplements Give Athletes an Edge?
WebMD Health Experts and Community
Converse with wellbeing specialists and other individuals like you in WebMD's Communities. It's a protected gathering where you can make or take an interest in care groups and discourses about wellbeing subjects that interest you.
Second OpinionWebMD
SECOND OPINION
Perused master points of view on well known wellbeing themes.
CommunityWebMD
Group
Interface with individuals like you, and get master direction on carrying on with a sound life.
WebMD
Pamphlets
Join to get WebMD's honor winning substance conveyed to your inbox.
Join
Seek
WebMD: Better data. Better wellbeing.
Omega-3 Fatty Acids May Stem Further Damage After Heart Attack
Seek
SUBSCRIBE
WebMD Home next page Heart Health Center next page Heart Health News Email a Friend Print Article
Heart Health Center
Offer this:
Tune in
Omega-3s May Stem Further Damage After Heart Attack
Survivors who took huge, day by day dosage of medicine just containers indicated less decrease in heart capacity
WebMD News from HealthDay
WebMD News Archive
By Robert Preidt
HealthDay Reporter
WEDNESDAY, March 4, 2015 (HealthDay News) - High measurements of omega-3 unsaturated fats may secure against further harm in heart assault patients, a preparatory study proposes.
The exploration included 374 heart assault survivors who got standard treatment and took either a 4-gram remedy just measurements of omega-3 unsaturated fats every day or a fake treatment. The specialists said that individuals most likely couldn't get that level of omega-3 unsaturated fats from eating regimen alone. To represent how substantial a measurements that is, the analysts noticed that 4 grams of omega-3 unsaturated fats is what might as well be called eating 8 ounces of salmon.
Utilizing MRIs, the patients' hearts were checked two weeks, four weeks and six months after their heart assault.
Contrasted with those taking the fake treatment, patients taking the omega-3 containers had lower levels of aggravation and were 39 percent less inclined to show disintegration of heart capacity. There was additionally less thickening or scarring of the ranges of the heart that were not straightforwardly harmed amid the heart assault. This thickening, otherwise called fibrosis, regularly creates when the surviving heart muscle works harder to make up for the harmed tissue, as indicated by the scientists.
Patients with a 5 percent ascend in the measure of omega-3 unsaturated fats in their blood appeared to be well on the way to profit by the supplements.
The study is to be introduced March 16 at the yearly meeting of the American College of Cardiology (ACC) in San Diego. Research exhibited at gatherings ought to be viewed as preparatory until distributed in a companion inspected diary.
"Giving a high measurement of fish oil [omega-3 greasy acids] not long after a heart assault seems to enhance cardiovascular structure and heart working well beyond the standard of consideration," senior study creator said Dr. Raymond Kwong in an ACC news discharge. He is chief of heart attractive reverberation imaging at Brigham and Women's Hospital in Boston.
"Since this is an extraordinary gathering of patients with surprisingly high adherence to [guideline-directed] medications for intense [heart attack] as of now, we feel genuinely sure that the advantages from the supplement are added substance. The ramifications of this study could be genuinely expansive," Kwong said.
Past examination has demonstrated that omega-3 unsaturated fats may bring down the danger of heart beat issues and demise from heart assault.
"Fish oil [omega-3 greasy acids] may have mitigating impacts furthermore advance better cardiovascular mending," Kwong said. "This is imperative in light of the fact that other mitigating operators, including steroids and NSAIDs, have neglected to have any kind of effect after [heart attack]."
Around 735,000 Americans endure a heart assault every year, as indicated by the U.S. Places for Disease Control and Prevention.
Eating nourishments rich in omega-3 unsaturated fats may bring down the danger of death from heart assault. This is the finding of new research distributed in JAMA Internal Medicine.
[Foods rich in omega-3]
Eating nourishments rich in omega-3 may lessen the danger of death from heart assault, say scientists.
Every year, around 735,000 individuals in the United States show some kindness assault, which happens when an area of the heart neglects to get enough oxygen-rich blood.
Embracing a solid eating regimen is viewed as a key variable in lessening the danger of heart assault, and numerous studies have proposed that including omega-3 polyunsaturated unsaturated fats as a major aspect of such an eating routine is especially useful for heart wellbeing.
Different concentrates, in any case, have scrutinized the heart advantages of omega-3s, with some recommending that fish oil supplements - a noteworthy wellspring of the unsaturated fats - don't bring down the danger of heart-related occasions.
Omega-3s are fundamental unsaturated fats that the body requirements for specific capacities, including blood coagulating, assimilation, muscle action, and cell division and development. In any case, the main way the body can get omega-3 is through the nourishments we eat.
Greasy fish -, for example, salmon, trout, fish, sardines, and anchovies - is a key wellspring of omega-3s, including eicosapentaenoic corrosive (EPA) and docosahexaenoic corrosive (DHA). Different sources incorporate verdant vegetables, walnuts, and some vegetable oils, which typically contain the omega-3 alphalinolenic corrosive (ALA).
For this most recent study, lead scientist Liana C. Del Gobbo, Ph.D., of the Division of Cardiovascular Medicine at Stanford University School of Medicine in California, and associates set out to pick up a superior comprehension of how omega-3s influence heart wellbeing.
In particular, they took a gander at how omega-3s got from fish and plant-based nourishments impact the danger of death from heart assault, or myocardial localized necrosis.
Danger of deadly heart assault 10 percent lower with higher omega-3 levels
The group investigated the information of 19 studies that included 45,637 people from crosswise over 16 nations, including the U.S., the United Kingdom, Italy, Norway, and Australia.
After some time, 7,973 of the members encountered a first-time heart assault, with 2,781 kicking the bucket thus.
The group found that members who had higher groupings of fish and plant-based omega-3s in their blood were around 10 percent less inclined to kick the bucket from heart assault, contrasted and members who had lower omega-3 fixations.
In any case, the scientists recognized no diminished danger of non-lethal heart assault with higher blood levels of fish and plant-based omega-3s, which they say shows there is a very particular component by which the unsaturated fats lower heart assault demise hazard.
These discoveries stayed subsequent to representing various conceivable puzzling variables, for example, members' age, sex, race/ethnicity, the nearness of diabetes, and utilization of headache medicine or cholesterol-bringing down medications.
Generally, the creators say their outcomes show that devouring sustenances rich in omega-3 may bring down the danger of non-deadly heart assault.
"During an era when a few however not different trials of fish oil supplementation have indicated advantages, there is vulnerability about cardiovascular impacts of omega-3s. Our outcomes loan backing to the significance of fish and omega-3 utilization as a feature of a sound eating regimen."
In case you're stressed over coronary illness, eating one to two servings of fish a week could lessen your danger of biting the dust of a heart assault.
For a long time, the American Heart Association has prescribed that individuals eat fish rich in omega-3 unsaturated fats at any rate twice per week. Specialists have since quite a while ago trusted that the unsaturated fats in fish, called omega-3 unsaturated fats, are the supplements that decrease the danger of kicking the bucket of coronary illness. Nonetheless, later research proposes that different supplements in fish or a blend of omega-3 unsaturated fats and different supplements in fish may really be in charge of the medical advantages from fish.
A few people are worried that mercury or different contaminants in fish may exceed its heart-sound advantages. Notwithstanding, with regards to a more beneficial heart, the advantages of eating fish as a rule exceed the conceivable dangers of introduction to contaminants. Discover how to adjust these worries with including a sound measure of fish to your eating regimen.
What are omega-3 unsaturated fats, and why are they useful for your heart?
Fish contain unsaturated fats, which, when substituted for soaked unsaturated fats, for example, those in meat, may bring down your cholesterol. In any case, the primary gainful supplement gives off an impression of being omega-3 unsaturated fats in greasy fish. Omega-3 unsaturated fats are a kind of unsaturated fat that may diminish irritation all through the body. Aggravation in the body can harm your veins and prompt coronary illness.
Omega-3 unsaturated fats may diminish triglycerides, lower pulse, lessen blood thickening, diminish stroke and heart disappointment hazard, decrease unpredictable heartbeats, and in youngsters may enhance learning capacity. Eating no less than one to two servings a week of fish, especially fish that is rich in omega-3 unsaturated fats, seems to decrease the danger of coronary illness, especially sudden cardiovascular passing.
Does it make a difference what sort of fish you eat?
Greasy fish, for example, salmon, lake trout, herring, sardines and fish, contain the most omega-3 unsaturated fats and in this manner the most advantage, yet numerous sorts of fish contain little measures of omega-3 unsaturated fats.
Are there any sorts of fish you ought to stay away from?
Some fish, for example, tilapia and catfish, don't have all the earmarks of being as heart sound since they contain larger amounts of unfortunate unsaturated fats. Remember that any fish can be undesirable relying upon how it's readied. For instance, cooking or heating fish is a more advantageous choice than is profound singing.
A few specialists are worried about eating fish delivered on homesteads instead of wild-got fish. Specialists think anti-infection agents, pesticides and different chemicals utilized as a part of raising cultivated fish may bring about destructive impacts to individuals who eat the fish.
What amount of fish would it be a good idea for you to eat?
For grown-ups, no less than two servings of omega-3-rich fish a week are suggested. A serving size is 3.5 ounces (99 grams), or about the measure of a deck of cards. Ladies who are pregnant or plan to wind up pregnant and youthful youngsters ought to restrain the measure of fish they eat on the grounds that they're most powerless to the potential impacts of poisons in fish.
Does mercury tainting exceed the medical advantages of eating fish?
The danger of getting an excessive amount of mercury or different contaminants from fish is for the most part exceeded by the medical advantages that omega-3 unsaturated fats have. The primary sorts of poisons in fish are mercury, dioxins and polychlorinated biphenyls (PCBs). The measure of poisons relies on upon the kind of fish and where it's gotten.
Mercury happens normally in little sums in the earth. In any case, mechanical contamination can deliver mercury that amasses in lakes, waterways and seas, which turns up in the sustenance fish eat. At the point when fish eat this sustenance, mercury develops in the collections of the fish.
Expansive fish that are higher in the evolved way of life —, for example, shark, tilefish, swordfish and lord mackerel — have a tendency to have more elevated amounts of mercury than do littler fish. Bigger fish eat the littler fish, increasing higher centralizations of the poison. The more extended a fish lives, the bigger it develops and the more mercury it can gather.
Pay consideration on the sort of fish you eat, the amount you eat and other data, for example, state advisories. Every state issues advisories with respect to the protected measure of privately got fish that can be expended.
Should anybody abstain from eating fish as a result of the worries over mercury or different contaminants?
On the off chance that you eat enough fish containing mercury, the poison can gather in your body. It can take the length of a year or more for your body to evacuate these poisons. Mercury is especially hurtful to the advancement of the mind and sensory system of unborn youngsters and youthful kids. For most grown-ups, in any case, it's improbable that mercury would bring about any wellbeing concerns.
Still, the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) prescribe that these gatherings restrain the measure of fish they eat:
Ladies who are pregnant or attempting to end up pregnant
Bosom bolstering moms
Youthful kids
Pregnant ladies, bosom bolstering moms and kids can at present get the heart-solid advantages of fish by eating fish that is normally low in mercury, for example, salmon, and constraining the sum they eat to:
Close to 12 ounces (340 grams) of fish altogether a week
Close to 6 ounces (170 grams) of canned fish a week
No measure of any fish that is ordinarily high in mercury (shark, swordfish, ruler mackerel and tilefish)
Are there whatever other concerns identified with eating fish?
A few late studies have connected abnormal amounts of omega-3 unsaturated fats in the blood to an expanded danger of prostate growth. However, these studies weren't decisive, and more research should be done to affirm this connection. Converse with your specialist about what this potential danger may intend to you.
Can you get the same heart-medical advantages by eating different sustenances that contain omega-3 unsaturated fats, or by taking omega-3 unsaturated fat supplements?
Eating fish rich in omega-3 unsaturated fats and different supplements seems to give more heart-sound advantages than does utilizing supplements. Other nonfish sustenance choices that do contain some omega-3 unsaturated fats incorporate flaxseed, flaxseed oil, walnuts, canola oil, soybeans and soybean oil. Be that as it may, like supplements, the confirmation of heart-solid advantages from eating these nourishments isn't as solid as it is from eating fish.
Omega-3 Fatty Acids and Coronary Heart Disease
Most Americans eat a lot of fat and an excessive number of calories. Alongside an absence of activity, this has prompted a pandemic of weight and diabetes. It's additionally added to keeping coronary illness as the main source of death in the United States. Be that as it may, shouldn't something be said about omega-3 unsaturated fats?
Omega-3s are a useful and critical type of fat, one that your body needs however can't make. In spite of the fact that your body needs 2 types of omega unsaturated fats, omega-3 and omega-6, it is the omega-3s that get high checks from specialists. They trust that omega-3s avert coronary illness (CHD) in sound individuals and moderate advancement of the ailment in the individuals who as of now have it.
Eating regimen and coronary illness
CHD is brought on by atherosclerosis. This is a long haul process in which greasy stores of plaque develop within the coronary conduits. These are the veins that supply the heart muscle with oxygen and supplements. Over the long haul, the coronary conduits turn out to be narrow to the point that the stream of blood to the heart muscle is diminished or effortlessly hindered by plaque or a blood coagulation. CHD can deliver mid-section torment, called angina, heart assault, or both.
Atherosclerosis starts when within mass of a supply route is harmed by aggravation or elevated amounts of cholesterol and triglycerides. Triglycerides is another type of fat in your blood. An eating routine high in fat, particularly soaked fat, builds cholesterol and triglycerides. Supply route harm can likewise be created by hypertension, tobacco smoke, or diabetes. You ought to keep your cholesterol and triglycerides at or beneath prescribed levels. This could avert coronary illness. As per the National Heart, Lung, and Blood Institute, that implies an aggregate cholesterol level of under 200 mg/dL and a triglyceride level of under 150 mg/dL.
Where omega-3s come in
Plate containing a serving of salmon finished with a cut of lemon. A fork is resting to the side.
To bring down your levels of cholesterol and triglycerides, you ought to keep up a solid weight, do modestly requesting physical movement most days of the week, eat an eating routine rich in vitamins, minerals, and fiber. Additionally incorporate fish containing omega-3 unsaturated fats in any event twice per week.
In the normal American's eating regimen, around 20% of calories that originate from fat are omega-3 and omega-6 unsaturated fats. The vast majority of the omega unsaturated fats are omega-6s. Specialists have found that individuals who eat nourishments with abnormal amounts of 2 of the omega-3 unsaturated fats, eicosapentaenoic corrosive (EPA), and docosahexaenoic corrosive (DHA), have low rates of CHD.
EPA and DHA are likewise called marine omega-3s since they are found in greasy fish like mackerel, lake trout, herring, sardines, tuna fish, and salmon. They are additionally in supplements called fish oils. Another hotspot for EPA and DHA is alpha-linolenic corrosive. This is found in soy and canola oils, flaxseed, walnuts, and different nuts. It can be changed into omega-3 unsaturated fats in the body, yet its advantage in forestalling coronary illness is not as clear.
Here's the way specialists trust omega-3 unsaturated fats may decrease the danger for CHD:
They bring down the danger for arrhythmia, a strange heart cadence, which can prompt sudden cardiovascular passing.
They bring down triglyceride levels.
They bring down the development rate of plaque that obstructs veins.
They bring down circulatory strain marginally.
They avert irritation of the veins and development of blood clumps.
What amount do you require?
The American Heart Association (AHA) prescribes that sound individuals who don't have coronary illness eat some sort of greasy fish at any rate twice every week. What's more, they ought to incorporate oils and nourishments rich in alpha-linolenic corrosive in their eating routine. Flaxseed, canola and soybean oils, and walnuts contain this corrosive.
Nourishment is the most ideal approach to get omega-3 unsaturated fats since sustenance contains other sound substances. For instance, fish contains arginine, glutamine, and selenium. These may advantage the heart and veins. Flaxseed and walnuts have substances that lower complete cholesterol.
The AHA offers this once-over on the omega-3 substance of some fish, per 3-ounce serving:
Canned light fish: 0.17 to 0.24 grams
Shrimp: 0.29 grams
Pollock: 0.45 grams
New or solidified salmon: 1.1 to 1.9 grams
Cod: 0.15 to 0.24 grams
Catfish: 0.22 to 0.3 grams
Shellfishes: 0.25 grams
Flop or sole: 0.48 grams
Crabs: 0.27 to 0.4 grams
Scallops: 0.18 to 0.34 grams
Disadvantages of fish
Eating fish accompanies a drawback. There are some wellbeing dangers. A few sorts of fish, particularly the more established, bigger savage fish, may contain large amounts of toxic substances. Check nearby advisories about the wellbeing of fish got by family and companions in your neighborhood lakes, streams, and seaside territories.
Methylmercury is found in shark, swordfish, ruler mackerel, and tilefish. Tilefish is likewise called brilliant bass or brilliant snapper. Methylmercury is most unsafe in extremely youthful youngsters and in ladies who are pregnant or prone to end up pregnant. Angle low in mercury are shrimp, canned light fish, salmon, pollock, and catfish.
Polychlorinated biphenyls (PCBs) are found in freshwater fish living in dirtied waters. PCBs may bring about disease. These fish incorporate lake trout, noticed, and freshwater bluefish. PCBs likewise are found in some cultivated fish like salmon. Dioxin and comparable mixes cause malignancy, discourage the resistant framework, and influence the focal sensory system. You ought to check nearby admonitory data before purchasing fish.
The advantages and dangers of eating fish change, contingent upon a man's phase of life. These are the AHA's proposals:
Youngsters, and pregnant and/or nursing ladies ought to maintain a strategic distance from possibly sullied fish, including shark, swordfish, ruler mackerel, and tilefish.
Moderately aged and more seasoned men, and ladies after menopause ought to take after rules from the FDA and Environmental Protection Agency on the amount of fish to securely eat. For this age assemble, the advantages of eating fish exceed the dangers.
You ought to eat an assortment of fish to diminishing conceivable hurtful impacts from ecological toxins.
Since the first American Heart Association (AHA) Science Advisory was distributed in 1996,1 imperative new discoveries have been accounted for about the advantages of omega-3 unsaturated fats on cardiovascular sickness (CVD). Omega-3 unsaturated fats are gotten from two dietary sources: fish and certain nut and plant oils. Fish and fish oils contain the 20-carbon eicosapentaenoic corrosive (EPA) and the 22-carbon docosahexaenoic corrosive (DHA), while canola, walnut, soybean, and flaxseed oils contain the 18-carbon α-linolenic corrosive (ALA). ALA gives off an impression of being less powerful than EPA and DHA. The proof supporting the clinical advantages of omega-3 unsaturated fats get from populace concentrates on and randomized, controlled trials, and new data has developed with respect to the components of activity of these supplements. These are laid out in a late Scientific Statement, "Fish Consumption, Fish Oil, Omega-3 Fatty Acids and Cardiovascular Disease."2
See page e20
Past Section
Next Section
What Do Epidemiologic and Clinical Studies Show?
Huge scale epidemiologic studies propose that individuals at danger for coronary illness (CHD) advantage from devouring omega-3 unsaturated fats from plants and marine sources. Despite the fact that the perfect add up to take is not immovably settled, proof from imminent auxiliary counteractive action thinks about recommends that admissions of EPA+DHA extending from 0.5 to 1.8 grams for every day (either as greasy fish or supplements) essentially lessen the quantity of passings from coronary illness and all causes. These information bolster the 2000 AHA Dietary Guidelines suggestion to incorporate no less than two servings of fish (especially greasy fish) every week. For ALA, an aggregate admission of 1.5 to 3 grams for every day appears to be valuable, albeit conclusive information from planned, randomized clinical trials are still required.
In randomized clinical trials (RCTs) that selected patients with coronary illness, omega-3 unsaturated fat supplements essentially diminished CV occasions (demise, nonfatal heart assaults, nonfatal strokes). Omega-3 supplements can likewise moderate the movement of atherosclerosis in these patients.
Past Section
Next Section
Instruments of Action
The ways that omega-3 unsaturated fats diminish CVD danger are as yet being considered. Nonetheless, research to date recommends that they can
diminish hazard for arrhythmias, which can prompt sudden heart demise.
diminish hazard for thrombosis, which can prompt heart assault and stroke.
diminish triglyceride and leftover lipoprotein levels.
diminish rate of development of the atherosclerotic plaque.
enhance endothelial capacity.
(somewhat) bring down circulatory strain.
decrease incendiary reactions.
Past Section
Next Section
AHA Recommendations
The AHA suggests that all grown-ups eat fish (especially greasy fish) no less than two times a week.3 Fish is a decent wellspring of protein and is low in soaked fat. Fish, particularly slick species like mackerel, lake trout, herring, sardines, tuna fish, and salmon, give huge measures of the two sorts of omega-3 unsaturated fats appeared to be cardioprotective, EPA and DHA. The AHA additionally suggests eating plant-inferred omega-3 unsaturated fats. Tofu and different types of soybeans; walnuts and flaxseeds and their oils; and canola oil all contain ALA.
For patients with reported CHD, the AHA suggests ≈1 g of EPA and DHA (joined) every day. This might be acquired from the utilization of slick fish or from omega-3 unsaturated fat cases, despite the fact that the choice to utilize the last ought to be made in interview with a doctor. The measure of EPA and DHA in fish and fish oil is exhibited in the late AHA Scientific Advisory on omega-3 unsaturated fats and CVD.2
An EPA+DHA supplement might be helpful in patients with hypertriglyceridemia. Two to four grams of EPA+DHA every day can bring down triglyceride 20% to 40%. Patients taking more than three grams of these unsaturated fats from supplements ought to do as such just under a doctor's consideration. High ("Eskimo") admissions could bring about over the top seeping in a few people.
Past Section
Next Section
Alerts
A few sorts of fish may contain critical levels of methylmercury, polychlorinated biphenyls (PCBs), dioxins, and other ecological contaminants. Levels of these substances are by and large most astounding in more established, bigger, ruthless fish and marine warm blooded animals. Two late epidemiologic studies have reported clashing discoveries about whether there is a relationship between methylmercury presentation and CHD, with one demonstrating a negative impact on CHD wellbeing in grown-up men,4 and the other reporting no relationship between methylmercury introduction and CHD in an extensive companion of male wellbeing professionals.5 While further studies are expected to determine this issue, it is critical to value that there are numerous types of fish that are rich wellsprings of omega-3 unsaturated fats that are low in methylmercury6 and that fish oil supplements are methylmercury-free.7
The advantages and dangers of eating fish fluctuate contingent upon a man's phase of life. Particular direction on fish utilization can be found on sites at the Environmental Protection Agency8 and the US Food and Drug Administration.9
Kids and pregnant and nursing ladies for the most part have low CVD chance however might be at higher danger of presentation to intemperate mercury from fish. Keeping away from conceivably sullied fish is a higher need for these gatherings.
For moderately aged and more seasoned men and for ladies after menopause, the advantages of eating fish far exceed the dangers when expended by rules of the US Food and Drug Administration and Environmental Protection Agency.
Eating an assortment of fish will minimize any conceivably unfriendly impacts because of ecological toxins.
Past Section
Next Section
Conclusion
Randomized trials have convincingly archived that omega-3 unsaturated fats can essentially diminish the event of CVD occasions in patients with coronary supply route ailment. The most grounded proof to date is from studies in which marine-determined omega-3 unsaturated fats have been expended as supplements or fish. Extra clinical studies are expected to affirm the cardioprotective advantages of ALA. A nourishment based way to deal with expanding omega-3 unsaturated fats is best, despite the fact that supplements are an appropriate option. Extra clinical and unthinking studies are expected to affirm and encourage characterize the medical advantages of omega-3 unsaturated fats for both essential and auxiliary anticipation.
Since the first AHA Science Advisory “Fish Consumption, Fish Oil, Lipids, and Coronary Heart Disease,”1 important new findings, including evidence from randomized controlled trials (RCTs), have been reported about the beneficial effects of omega-3 (or n-3) fatty acids on cardiovascular disease (CVD) in patients with preexisting CVD as well as in healthy individuals.2 New information about how omega-3 fatty acids affect cardiac function (including antiarrhythmic effects), hemodynamics (cardiac mechanics), and arterial endothelial function have helped clarify potential mechanisms of action. The present Statement will address distinctions between plant-derived (α-linolenic acid, C18:3n-3) and marine-derived (eicosapentaenoic acid, C20:5n-3 [EPA] and docosahexaenoic acid, C22:6n-3 [DHA]) omega-3 fatty acids. (Unless otherwise noted, the term omega-3 fatty acids will refer to the latter.) Evidence from epidemiological studies and RCTs will be reviewed, and recommendations reflecting the current state of knowledge will be made with regard to both fish consumption and omega-3 fatty acid (plant- and marine-derived) supplementation. This will be done in the context of recent guidance issued by the US Environmental Protection Agency and the Food and Drug Administration (FDA) about the presence of environmental contaminants in certain species of fish.
Previous Section
Next Section
Epidemiological and Observational Studies
Coronary Heart Disease
As reviewed by Stone,1 three prospective epidemiological studies within populations reported that men who ate at least some fish weekly had a lower coronary heart disease (CHD) mortality rate than that of men who ate none.3–6⇓⇓⇓ More recent evidence that fish consumption favorably affects CHD mortality, especially nonsudden death from myocardial infarction (MI), has been reported in a 30-year follow-up of the Chicago Western Electric Study.7 Men who consumed 35 g or more of fish daily compared with those who consumed none had a relative risk of death from CHD of 0.62 and a relative risk of nonsudden death from MI of 0.33. In an ecological study conducted by Zhang et al,8 fish consumption was associated with a reduced risk from all-cause, ischemic heart disease and stroke mortality across 36 countries. In addition, in a study of Japanese living in Japan or Brazil, Mizushima et al9 reported a dose-response relationship between the frequency of weekly fish intake and reduced CVD risk factors (eg, obesity, hypertension, glycohemoglobin, ST-T segment change on the ECG). Until recently, little information was available about the effects of fish and omega-3 fatty acids and risk of CHD in women. A recent study conducted with women in the Nurses’ Health Study10 reported an inverse association between fish intake and omega-3 fatty acids and CHD death. Compared with women who rarely ate fish (less than once per month), the risk for CHD death was 21%, 29%, 31%, and 34% lower for fish consumption 1 to 3 times per month, once per week, 2 to 4 times per week, and >5 times per week, respectively (P for trend=0.001). Comparing the extreme quintiles of fish intake, the reduction in risk for CHD deaths seemed to be stronger for CHD death than for nonfatal MI (RR 0.55 versus 0.73).
Some studies have not reported a beneficial association of fish consumption and CHD mortality. In the Health Professionals’ Follow-up Study,11 no significant association was observed between fish intake (and omega-3 fatty acids) and risk of any CHD (ie, fatal coronary disease including sudden death, nonfatal MI, coronary artery bypass grafting, or angioplasty). Likewise, the US Physicians’ Health Study did not show an association between fish consumption (or omega-3 fatty acid intake) and reduced risk of total MI, nonsudden cardiac death, or total cardiovascular mortality.12 In contrast, however, fish consumption was related to a reduced risk of total mortality. The lack of an association between fish intake and CHD incidence and mortality also was reported from an analysis of the Seven Countries data and the EURAMIC (European Multicenter Case-Control Study on Antioxidants, Myocardial Infarction and Breast Cancer) Study.13,14⇓ In the Seven Countries Study, although an inverse association between fish consumption and 25-year mortality from CHD across several populations was observed,13 when the confounding effects of saturated fatty acids, flavonoids, and smoking were considered, the association was not significant. In the EURAMIC Study, a large international case-control study, no evidence of a protective effect of adipose tissue DHA (a measure of long-term fish consumption) on the risk of developing MI was seen.14
Some investigators have speculated that the conflicting data from the epidemiological studies reflect differences in definitions of sudden death and the residual confounding of reference groups that had a less healthy lifestyle, 15 variability in the end points studied, experimental design or how fish intake was estimated, different study populations,16 and the possible confounding effect of an increase in hemorrhagic stroke. Albert et al12 proposed that their lack of an association may have been due to the small fraction of their study population (3.1%) reporting little to no fish consumption. Only studies including sizable non–fish-eating populations have reported an inverse association between fish consumption and coronary mortality. In the EURAMIC Study, only survivors of MI were evaluated, and it is conceivable that individuals who did not survive ate less fish. Another explanation, based on a rigorous analysis of 11 prospective cohort studies, is that the protective effect of fish consumption relates to the CHD risk status of the population studied17; this analysis concluded that fish consumption reduced CHD mortality (RR=0.4 to 0.6) in high-risk but not low-risk populations. Another consideration relates to the type of fish consumed (ie, fatty versus lean fish). Oomen et al18 reported a lower CHD mortality (RR=0.66) in populations that consumed fatty fish but not lean fish.
Finally, another explanation for the discordant results of epidemiological studies pertains to the hypothesized adverse effects of methylmercury, an environmental contaminant found in certain fish that may diminish the health benefits of omega-3 fatty acids.19 Recent studies have produced conflicting results with regard to the effects of methylmercury on CHD risk.20,21⇓ Thus, the extent to which methylmercury in fish may mask the beneficial effects of omega-3 fatty acids requires further study.
Fish consumption has been shown to be related to reduced sudden cardiac death. In a population-based, nested, case-control study, a strong negative relationship was reported between fish intake and risk for sudden death (ie, 5.5 g of omega-3 fatty acids per month, equivalent to two fatty fish meals per week, was associated with a 50% reduced risk of primary cardiac arrest).22 In the US Physicians’ Health Study, men who consumed fish at least once weekly had a relative risk of sudden death of 0.48 (P=0.04) versus men who consumed fish less than once per month.12 A recent report from the Physicians’ Health Study23 reported an inverse relationship between blood levels of long-chain omega-3 fatty acids and risk of sudden death in men without a history of CVD. The relative risk of sudden death was significantly lower among men with levels in the third quartile (RR=0.28) and the fourth quartile (RR=0.19) compared with men whose blood levels were in the first quartile.
Further evidence for a protective effect of omega-3 fatty acids comes from two recent studies by Landmark et al24,25⇓ who reported that chronic intake of fish or fish oil was associated with a reduction in infarct size as estimated by the frequency of Q-wave infarcts and by peak creatine kinase and lactate dehydrogenase activities after MI. In contrast to all the studies demonstrating a beneficial association, the Alpha- Tocopherol, Beta-Carotene Cancer Prevention Study found that estimated omega-3 fatty acid intake from fish was associated with a trend toward increased relative risk of coronary death after adjustment for trans, saturated, and cis-monounsaturated fatty acids.26
A growing body of evidence from recent epidemiological studies indicates that α-linolenic acid is associated with a lower risk of MI and fatal ischemic heart disease in women and in men. In the EURAMIC Study, Guallar et al14 compared the highest quintile of adipose tissue α-linolenic acid to the lowest and found a relative risk for MI of 0.42 (P for trend=0.02). This became nonsignificant after adjusting for classic risk factors (primarily smoking). Using a food-frequency questionnaire from a 10-year follow-up of the Nurses’ Health Study, and after controlling for standard coronary risk factors, Hu et al27 reported a dose-response relationship between α-linolenic acid intake and relative risk of fatal ischemic heart disease, which was reduced by 45% in the highest quintile (P for trend=0.01). Similar findings were reported with the same methodology in the all-male Health Professionals’ Study, in which a 1% increase in α-linolenic acid intake was associated with a 0.41 relative risk for acute MI (P for trend=0.01).28 Lowest-quintile intakes of α-linolenic acid in these latter two trials were 0.7 to 0.8 g/d, and highest quintile intakes, 1.4 to 1.5 g/d. In the National Heart, Lung, and Blood Institute Family Heart Study, a cross-sectional study with 4584 participants, α-linolenic acid was inversely related to coronary artery disease.29 The prevalence odds ratio of coronary artery disease was reduced ≈40% for men in the top three quintiles of α-linolenic acid intake and ≈50% to 70% for women. In contrast, in the Zutphen Elderly Study, a prospective epidemiological study with 667 men, ages 64 to 84 years, there was no beneficial effect of α-linolenic acid intake on risk of 10-year coronary artery disease incidence.30 In the latter study, however, these negative results have been explained by the association between α-linolenic acid and trans-fatty acid intake,30 as well as by limitations in the collection of the dietary data.31 Despite this latter study, a growing epidemiological database demonstrates a protective effect of α-linolenic acid on coronary disease. Nonetheless, intervention studies are needed to establish a causal relationship between α-linolenic acid intake and coronary disease.
Stroke
Compared with the literature describing the effects of omega-3 fatty acids on CHD, relatively little information about the association of omega-3 fatty acids and cerebral infarctions (stroke) is available. Several epidemiological studies have examined the relationship between fish intake and stroke incidence. In the Zutphen Study, the unadjusted hazard ratio of men who consumed an average of 20 g/d of fish was 0.49 (P<0.05) compared with those who consumed less.32 Likewise, in the National Health and Nutrition Examination Survey (NHANES) Epidemiologic Follow-up Study, white females who consumed fish more than once per week had an age-adjusted stroke incidence that was only half that of women who reported not consuming fish.33 A similar protective effect was seen in both black women and men but not in white men. A trend (P=0.06) toward reduced risk for stroke with increasing reported fish consumption was also reported in the Nurses’ Health Study.34 In contrast, both the Chicago Western Electric Study35 and the Physicians’ Health Study36 failed to find any relationship between reported fish intake and reduced stroke risk.
According to the serum fatty acid profiles of subjects in the Multiple Risk Factor Intervention Trial, α-linolenic acid was negatively associated with stroke incidence.37 In both the Lyon Diet Heart Study38 (testing a Mediterranean-style diet enriched with α-linolenic acid) and the GISSI-Prevention Study39 (testing the effects of 850 mg of supplemental omega-3 fatty acids), there was no significant effect on the incidence of stroke.
The evidence to date is primarily for total stroke risk, and associations could differ if the data were analyzed for type-specific stroke incidence. For example, evidence exists for an inverse relationship between small intakes of fish (1 portion per week) and ischemic stroke32 and for a possible increased risk for hemorrhagic stroke with “Eskimo” intakes of omega-3 fatty acids.40 Thus, as Zhang et al8 have noted, linking fish consumption with total stroke risk is likely to underestimate the strength of the real associations between fish consumption and type-specific stroke risk.
Previous Section
Next Section
Randomized Controlled Trials
At the time of the first Advisory, the only RCT of omega-3 fatty acids in secondary prevention of CHD was the Diet And Reinfarction Trial (DART), which reported a 29% reduction in all-cause mortality over a 2-year period in male MI survivors advised to increase their intake of oily fish (200 to 400 g of fatty fish per week, which provided an additional 500 to 800 mg/d of omega-3 fatty acids).41 The greatest benefit was seen in fatal MIs, and this observation led to the hypothesis that omega-3 fatty acids might protect the myocardium against the adverse sequela of acute ischemic stress. A post hoc analysis of patients receiving fish oil capsules (900 mg/d of EPA+DHA) in DART suggested that the protective effect was attributable to omega-3 fatty acids.42
The first of three recent RCTs designed to detect the effects of supplemental EPA and DHA on clinical events was reported by Singh et al.43 Patients admitted to the hospital with suspected acute MIs were randomized to either fish oil capsules (containing 1.8 g/d of EPA+DHA), mustard oil (20 g/d providing 2.9 g α-linolenic acid), or placebo. After one year, total cardiac events were 25% and 28% in the fish oil and mustard oil groups, respectively, versus 35% in the placebo group (P<0.01). As in the DART, nonfatal MIs were significantly lower in the fish oil and mustard oil groups.
The largest prospective RCT to test the efficacy of omega-3 fatty acids for secondary prevention of CHD is the GISSI-Prevention Study.39 In this study, 11 324 patients with preexisting CHD (who were receiving conventional cardiac pharmacotherapy) were randomized to either 300 mg of vitamin E, 850 mg of omega-3 fatty acid ethyl esters (as EPA and DHA), both, or neither. After 3.5 years of follow-up, the group given the omega-3 fatty acids alone experienced a 15% reduction in the primary end point of death, nonfatal MI, and nonfatal stroke (P<0.02). There was a 20% reduction in all-cause mortality (P=0.01) and a 45% reduction in sudden death (P<0.001) compared with the control group; vitamin E provided no additional benefit. Triglycerides decreased by 4% and LDL cholesterol levels increased by 2.5% after six months in the omega-3 fatty acid treatment groups compared with controls. This trial, although very large and carried out in a relatively “usual-care” setting, was not placebo controlled, and dropout rates were high (>25%). A follow-up study44 assessed the time-course of the benefit of omega-3 fatty acids on mortality in subjects in the GISSI Study and found that survival curves diverged early after randomization. Total mortality was significantly lowered after 3 months of treatment (RR=0.59), and by 4 months, risk of sudden death was reduced (RR=0.47).
In contrast to the growing body of evidence supporting a protective effect of omega-3 fatty acids in secondary prevention, a recent study reported no effect of 3.5 g/d of DHA+EPA versus corn oil on cardiac events in post-MI patients (n=300) after 1.5 years of intervention.45 The authors speculated that the lack of an omega-3 fatty acid effect may have been due to the high habitual fish intake in western Norway, which could have afforded maximal protection beyond which no additional effects would be expected. Thus, further research is needed to confirm and further define the role of omega-3 fatty acid supplements for secondary prevention of coronary disease.
The first study to explore the effects of omega-3 fatty acids on angiographic progression rates provided 59 patients either 6 g/d of omega-3 fatty acids or olive oil for 2 years.46 No benefit was observed. More recently, a larger trial using lower and more practical intakes of omega-3 fatty acids has been reported.47 Patients presenting for coronary angiography (n=223) were randomized to either placebo or omega-3 fatty acids (3 g/d for 3 months followed by 1.5 g/d for 21 months). The latter group exhibited significantly (P=0.04) less progression, more regression, and a trend toward fewer clinical events (7 versus 2, P=0.1). Finally, Eritsland et al48 reported that in 610 patients undergoing coronary artery bypass grafting, the provision of 3.4 g of omega-3 fatty acid ethyl esters lowered vein graft occlusion rates from 33% (control) to 27% (P=0.03).
Several randomized trials of fish oil were conducted over the past 10 years to test the hypothesis that omega-3 fatty acids could prevent restenosis after percutaneous transluminal coronary angioplasty. Although a meta-analysis of seven early trials concluded that supplementation was beneficial,49 more recent trials (with large study populations given 5 to 7 g/d of omega-3 fatty acids) have not supported this conclusion.50,51⇓ Most investigators have concluded that further trials are not warranted.
The question of the efficacy of α-linolenic acid in CHD prevention has been examined in four trials. The Indian Experiment of Infarct Survival43 discussed above reported a significant decrease in total cardiac events in the group assigned to mustard seed oil. The Lyon Heart Trial was a secondary prevention trial designed to test whether a Mediterranean-type diet (including increased amounts of α-linolenic acid) would reduce reoccurrence rates of cardiac events compared with a prudent Western diet.38,52⇓ Marked reductions were seen in cardiac death and nonfatal MI, major secondary end points, and minor events. The difference in intakes of α-linolenic acid between groups was 0.5 versus 1.5 g/d. It is impossible, however, to ascribe the benefit unambiguously to α-linolenic acid because many other dietary variables were present: Saturated fat and cholesterol decreased and monounsaturated fat increased, as did the consumption of fruits and vegetables.
Although the Indian Experiment of Infarct Survival43 and the Lyon Heart Trial38 provide clinical trial evidence in support of a beneficial effect of α-linolenic acid, the Norwegian Vegetable Oil Experiment53 and the Mediterranean Alpha-Linolenic Enriched Groningen Dietary Intervention (MARGARIN) Study54 do not. The Norwegian Vegetable Oil Experiment was a double-blind RCT in which >13 000 men ages 50 to 59 with no history of MI were randomized to consume 5.5 g/d of α-linolenic acid (from 10 mL of linseed oil) or 10 mL of sunflower seed oil for one year. There were 27 cases of new CHD or sudden death in each group, and 40 versus 43 deaths from any cause in the control versus the linseed oil groups. In the MARGARIN Study, free-living subjects (n=124 men and 158 women) with multiple CVD risk factors were provided with margarines high in either α-linolenic acid or linoleic acid and followed up for 2 years.54 According to effects on CVD risk factors, the 10-year estimated ischemic heart disease risk decreased similarly in both groups (2.1% and 2.5%, respectively). Of note, however, was a trend toward fewer CVD events in the α-linolenic acid group (1.8% versus 5.7%, P=0.20). It is important that additional studies be conducted to clarify the role of α-linolenic acid in reducing CHD risk.
In aggregate, available RCTs show a beneficial effect of dietary and supplemental omega-3 fatty acids, including both EPA+DHA and α-linolenic acid, on CHD. This has been summarized in a recent meta-analysis of 11 RCTs with 7951 patients in the intervention groups.55 In this meta-analysis, the risk ratio of nonfatal MI was 0.8, for fatal MI it was 0.7, and for sudden death (in 5 trials) it was 0.7.
Previous Section
Next Section
Possible Mechanisms
The mechanisms responsible for the observed effects of omega-3 fatty acids on cardiovascular health are not known with confidence, especially at the low intakes utilized in the DART and GISSI Prevention Study. Those possibly involved are summarized in Table 1.56
View this table:
In this window In a new window
TABLE 1. Potential Mechanisms by Which Omega-3 Fatty Acids May Reduce Risk for Cardiovascular Disease
Triglycerides
The hypotriglyceridemic effects of omega-3 fatty acids from fish oils are well established. In a comprehensive review of human studies, Harris57 reported that ≈4 g/d of omega-3 fatty acids from fish oil decreased serum triglyceride concentrations by 25% to 30%, with accompanying increases in LDL cholesterol of 5% to 10% and in HDL cholesterol of 1% to 3%. A dose-response relationship exists between omega-3 fatty acid intake and triglyceride lowering.57 Postprandial triglyceridemia is especially sensitive to chronic omega-3 fatty acid consumption,58,59⇓ with quite small intakes (<2 g/d) producing significant reductions.60 The plasma lipid and lipoprotein responses to fish oil are comparable in diabetic and nondiabetic subjects.61 In addition, a recent meta-analysis of 26 trials of subjects with type 1 or type 2 diabetes mellitus reported no effects of fish oil on hemoglobin A1c,62 although fasting blood glucose levels rose slightly in the latter group.
Fish oil can have a therapeutic role in the treatment of marked hypertriglyceridemia (>750 mg/dL). Effective doses of omega-3 fatty acids range from 3 to 5 g/d, which can only be obtained consistently by supplementation. At present, it seems that both EPA and DHA have triglyceride-lowering properties.63 Patients taking >3 g of EPA+DHA from supplements should do so only under a physician’s care because the FDA has noted that an intake in excess of this level could result in excessive bleeding in some individuals.64 In contrast, cardioprotective intakes seem to be considerably lower (≈1 g/d), have almost no potential for adverse effects, and can be achieved by diet.
Blood Pressure
Omega-3 fatty acids seem to have a small, dose-dependent, hypotensive effect, the extent of which seems to be dependent on the degree of hypertension.65 In a meta-analysis, Morris et al66 found a significant reduction in blood pressure of −3.4/−2.0 mm Hg in studies with hypertensive subjects who consumed 5.6 g/d of omega-3 fatty acids. Likewise, Appel et al67 found that blood pressure was decreased −5.5/−3.5 mm Hg in trials of untreated hypertensives given >3 g/d of omega-3 fatty acids. DHA seems to be more effective than EPA in lowering blood pressure.68 Still, in view of the high dose required to lower blood pressure and the proven efficacy of other nutritional factors and of antihypertensive medications, an increased intake of omega-3 fatty acids has a limited role in the management of hypertension.
Thrombosis and Hemostasis
Omega-3 fatty acids decrease platelet aggregation,69,70⇓ resulting in a modest prolongation of bleeding times (reviewed by Knapp71). Some evidence indicates that fish oil supplementation may enhance fibrinolysis.72 Although omega-3 fatty acid intake has been negatively associated with levels of fibrinogen, Factor VIII, and von Willebrand factor,73 more recent evidence from the Coronary Artery Risk Development In young Adults (CARDIA) study found no significant associations between customary intakes of fish (4 to 39 g/d) and omega-3 fatty acids (0.9 to 4.1 g/d) and these coagulation factors.74 Marckmann et al75 also found no effect of omega-3 fatty acids (0.9 g/d) on levels of Factor VII, fibrinogen, endogenous fibrinolysis, β-thromboglobulin, and von Willebrand factor. In contrast, a recent study reported that coronary patients taking 5.1 g/d of omega-3 fatty acids for 6 months experienced a reduction in von Willebrand factor (128% versus 147% for controls) and thrombomodulin (25 versus 33 ng/mL).76 Although it seems clear that omega-3 fatty acids beneficially influence collagen-induced platelet aggregation (thereby affecting hemostasis), their effects on thrombosis remain unclear. There is little evidence to suggest that an intake <3 g/d of omega-3 fatty acids would cause clinically significant bleeding.
Arrhythmias
The possibility that omega-3 fatty acids (including α-linolenic acid) may reduce risk for sudden cardiac death is based on evidence from a prospective cohort study,12 a case-control study,22 and four prospective dietary intervention trials.38,39,41,43⇓⇓⇓ Proposed mechanisms to explain these observations center not on lipid or blood pressure lowering or on antithrombotic effects, but on a novel stabilizing effect of omega-3 fatty acids on the myocardium itself. Evidence for a direct effect of these fatty acids on the heart has come from several observations. First, increased heart rate variability in survivors of MI was associated with the consumption of one fish meal per week77 or fish oil supplements (4.3 g/d of omega-3 fatty acids).78 Increases in this parameter predict a lower risk of mortality due to arrhythmic events in post-MI patients. EPA and DHA also have been shown to reduce resting heart rate and increase left ventricular filling capacity.79 Animal experiments and cell culture studies have shown that fish oil has potent antiarrhythmic effects. For example, studies with rats80 and dogs81,82⇓ have shown that pretreatment with omega-3 fatty acids reduced damage to cardiac tissue and forestalled the development of ventricular dysrhythmias when heart attacks were induced. Similar observations were made in fish oil–fed cats that were protected from cerebral damage after stroke induction.83 In vitro induction of tachyarrhythmias in cultured neonatal rat ventricular myocytes by various pharmacological agents (such as ouabain) can be prevented or abolished by the addition of omega-3 fatty acids to the culture medium (reviewed by Kang and Leaf84). This seems to be due to the ability of omega-3 fatty acids to prevent calcium overload by maintaining the activity of L-type calcium channels during periods of stress,85 and to increase the activity of cardiac microsomal Ca2+/Mg2+-ATPase.79 In addition, omega-3 fatty acids (including α-linolenic acid) are potent inhibitors of voltage-gated sodium channels in cultured neonatal cardiac myocytes, which may contribute to the reduction in arrhythmia.84
Other Biological Effects
Goode et al86 showed that acetylcholine-stimulated relaxation of small arteries taken from hypercholesterolemic patients was significantly improved after three months of supplementation with 3 g/d of EPA+DHA. Fish oil feeding has also been shown to improve endothelial function (reviewed by Chin and Dart87) and to increase arterial compliance.88 These effects may be secondary to fish oil’s ability to enhance nitric oxide production89 and may be the mechanism by which fish oil elicits a small hypotensive effect.
Mechanisms to explain the antiatherogenic (inhibition of new plaque development) effect of omega-3 fatty acids have recently been proposed.48 For example, EPA and DHA seem to alter the metabolism of adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and intercellular adhesion molecule-1 (ICAM-1). Abe et al (1998)90 reported a 9% reduction in soluble ICAM-1 and a 16% reduction in soluble E-selectin but not in soluble VCAM-1 in hypertriglyceridemic subjects receiving 3.4 g/d of highly purified omega-3 fatty acid ethyl esters for 7 to 12 months. There is also in vitro evidence that DHA reduces endothelial expression of VCAM-1 and the expression of E-selectin, ICAM-1, interleukin (IL)-6, and IL-8 in stimulated cells.91,92⇓ On the other hand, a study in male smokers with hyperlipidemia showed that six weeks of omega-3 fatty acid supplementation (4.8 g/d) increased soluble forms of E-selectin and VCAM-1.93 A subsequent study in coronary patients given supplemental omega-3 fatty acids (5.1 g/d for 6 months) found similar results.76 Fish oil also affects the metabolism of inflammatory mediators like the interleukins and tumor necrosis factor-α,94 molecules also believed to play a role in atherogenesis and plaque stability.95
Another potential antiatherogenic mechanism of omega-3 fatty acids is their interference with the arachidonic acid cascade that generates a wide variety of eicosanoids (reviewed by Uauy et al96). EPA not only can replace arachidonic acid in phospholipid bilayers, but it is also a competitive inhibitor of cyclooxygenase, reducing the production of the 2-series prostaglandins, thromboxanes, and prostacyclins and the 4-series leukotrienes. The 3- and 5-series (respectively) produced from EPA are generally less biologically active. DHA, although not a direct inhibitor of arachidonic acid metabolism, nevertheless can inhibit platelet aggregation by reducing the affinity of platelet TxA2/PGH2 receptor for its ligand.97 The net effects of omega-3 fatty acids are thus to reduce inflammatory processes, vasoconstriction, and platelet aggregation, all known to be antiatherogenic.
Some studies have shown that omega-3 fatty acids may increase the susceptibility of LDL to oxidation,98,99⇓ whereas others have not.100–102⇓⇓ It therefore remains to be established whether LDL oxidative status in vivo is affected by omega-3 fatty acids and, if so, whether this has any adverse clinical implications. Our current inability to identify and quantify in vivo oxidative damage and to relate it to clinical outcomes makes it difficult to draw firm conclusions about the impact of omega-3 fatty acids on these processes.
Previous Section
Next Section
Intake of Omega-3 Fatty Acids
The intake of total omega-3 fatty acids in the United States is ≈1.6 g/d (≈0.7% of energy intake).103 Of this, α-linolenic acid accounts for ≈1.4 g/d, and only 0.1 to 0.2 g/d comes from EPA and DHA. The major food sources of α-linolenic acid are vegetable oils, principally canola and soybean oils. Other food sources that are rich in α-linolenic acid (Table 2)104 include flaxseed (23 g/100 g) and English walnuts (7 g/100 g). Although some α-linolenic acid is converted to the longer-chain omega-3 fatty acids, the extent of this conversion is modest and controversial. For example, Emken et al105 reported a 15% conversion, whereas Pawlosky et al106 found 0.2%; both reported that the conversion to DHA was much less than that to EPA. Fish are the major food source of EPA and DHA (Table 3).104 All fish contain EPA and DHA; however, the quantities vary among species and within a species according to environmental variables such as diet and whether fish are wild or farm-raised. Farm-raised catfish tend to have less EPA and DHA than do wild catfish, whereas farm-raised salmon and trout contain similar amounts versus their wild counterparts.
View this table:
In this window In a new window
TABLE 2. α-Linolenic Acid Content of Selected Vegetable Oils, Nuts, and Seeds
View this table:
In this window In a new window
TABLE 3. Amounts of EPA+DHA in Fish and Fish Oils and the Amount of Fish Consumption Required to Provide ≈1 g of EPA+DHA per Day
A number of countries (Canada, Sweden, United Kingdom, Australia, Japan) as well as the World Health Organization and North Atlantic Treaty Organisation have made formal population-based dietary recommendations for omega-3 fatty acids. Typical recommendations are 0.3 to 0.5 g/d of EPA+DHA and 0.8 to 1.1 g/d of α-linolenic acid. Recently, the Food and Nutrition Board, Institute of Medicine, and The National Academies, in collaboration with Health Canada, released the Dietary Reference Intakes for Energy and Macronutrients.107 The Acceptable Macronutrient Distribution Range (AMDR) for α-linolenic acid is estimated to be 0.6% to 1.2% of energy, or 1.3 to 2.7 g/d on the basis of a 2000-calorie diet. This is ≈10 times the current intake of EPA+DHA. The lower boundary of the range is based on an Adequate Intake set for α-linolenic acid, which represents median intake levels that prevent an essential fatty acid deficiency. The upper boundary corresponds to the highest α-linolenic acid intakes from foods consumed by individuals in the United States and Canada. Thus, the intent of the AMDR range for omega-3 fatty acids is to provide guidance for healthy people, not to prevent chronic disease. These recommendations can easily be met by following the AHA Dietary Guidelines to consume two fish meals per week, with an emphasis on fatty fish (ie, salmon, herring, and mackerel), and by using liquid vegetable oils containing α-linolenic acid. Commercially prepared fried fish (eg, from restaurants and fast food establishments, as well as many frozen, convenience-type fried fish products) should be avoided because they are low in omega-3 and high in trans-fatty acids.
Patients with CHD should be encouraged to increase their consumption of EPA and DHA to ≈1 g/d, which is the dose used in the GISSI-Prevention Study. Table 3 presents omega-3 fatty acid content of various fish and supplements as well as the amount required each day to provide ≈1 g/d of EPA+DHA. Although this level of EPA and DHA intake potentially can be attained through fish consumption, the requisite amount of fish intake may be difficult to achieve and sustain over the long term. For those individuals who do not eat fish, have limited access to a variety of fish, or cannot afford to purchase fish, a fish oil supplement may be considered. Depending on the preparation, up to three 1-g fish oil capsules per day will be necessary to provide ≈1 g/d of omega-3 fatty acids. The most common fish oil capsules in the United States today provide 180 mg of EPA and 120 mg DHA per capsule. It is important that consumers read the nutrition label to determine EPA and DHA levels in the fish oil capsule.
Previous Section
Next Section
Safety of Omega-3 Fatty Acids
Omega-3 fatty acids have been a part of the human diet for millennia. It has been estimated that the ratio of omega-6 to omega-3 fatty acids in the diet of early humans was 1:1.108 The ratio in the United States today has risen to ≈10:1 because of the combination of reduced omega-3 fatty acid intake and the widespread use of vegetable oils rich in linoleic acid.103 Because of the well-known competition between the omega-6 linoleate and the omega-3 α-linolenate for metabolic conversion to longer-chain, physiologically active metabolites, reducing the former while increasing the latter (or simply increasing the latter) is a strategy for increasing tissue levels of omega-3 fatty acids.109 Another obvious strategy is to simply consume more EPA and DHA, an approach that minimizes the significance of the ratio.
Since the first omega-3 fatty acid advisory,1 the FDA has ruled that intakes of up to 3 g/d of marine omega-3 fatty acids are GRAS (Generally Recognized As Safe) for inclusion in the diet.110 This ruling included specific consideration of the reported effects of omega-3 fatty acids on glycemic control in patients with diabetes, on bleeding tendencies, and on LDL cholesterol. Moreover, the FDA recently has approved a qualified health claim for EPA and DHA omega-3 fatty acids in dietary supplements.64
Although the safety of low intakes does not seem to be an issue, and supplements are essentially mercury free, some side effects of omega-3 fatty acid supplementation do occur (Table 4).111 Perhaps the most common is a fishy aftertaste. In the GISSI Prevention study, which provided 0.85 g of omega-3 fatty acids per day for 3.5 years, 3.8% of patients discontinued taking their supplements (compared with 2.1% for the vitamin E group). Gastrointestinal disturbances and nausea were the most commonly reported side effects, with 4.9% and 1.4% reported, respectively, compared with 2.9% and 0.4% in the vitamin E group. When 12 capsules containing 6 g of omega-3 fatty acids were fed to 41 patients for 2.4 years, three patients dropped from the study claiming intolerance to the capsules.46 In a 6-month trial providing 275 patients with 6.9 g of EPA+DHA in 10 capsules daily, there was no difference between the fish oil and corn oil control groups for any adverse event.112 Gastrointestinal upset was reported by 8% of the latter and 7% of the former. Finally, although refined and concentrated omega-3 fatty acid products contain virtually no methylmercury and are very low in organochloride contaminants,113 less well-controlled preparations can contain appreciable amounts.114
View this table:
In this window In a new window
TABLE 4. Risk for Side Effects From Ingestion of Omega-3 Fatty Acids
Previous Section
Next Section
Safety of Fish
Some species of fish may contain significant levels of methylmercury, polychlorinated biphenyls (PCBs), dioxins, and other environmental contaminants. These substances are present at low levels in fresh waters and oceans, and they bioconcentrate in the aquatic food chain such that levels are generally highest in older, larger, predatory fish and marine mammals.
Fish and seafood are a major source of human exposure to these contaminants. PCBs and methylmercury have long half-lives in the body and can accumulate in people who consume contaminated fish on a frequent basis. Consumers can reduce their exposure to PCBs by removing the skin and fat from these fish before cooking them; however, because methylmercury is distributed throughout the muscle, skinning and trimming does not significantly reduce mercury concentrations in filets.
The responsibility for regulating the quality of the fish for human consumption is shared by the states and two federal agencies. The Environmental Protection Agency regulates sport-caught fish, whereas the FDA regulates all commercial fish—including farm-raised, imported, and marine fish. The Environmental Protection Agency’s 2000 National Listing of Fish and Wildlife Advisories may be found on the Environmental Protection Agency web site.115 The Environmental Protection Agency advises women who are pregnant or may become pregnant and nursing mothers to limit their consumption of sport-caught fish to one 6-ounce meal per week.116 The Environmental Protection Agency also recommends that young children consume ≤2 ounces of sport-caught fish per week. The FDA recommends that women who are pregnant or nursing and young children eliminate shark, swordfish, king mackerel in the mackerel family, and tilefish (also referred to as golden bass or golden snapper) from their diets completely and limit their consumption of other fish to 12 ounces per week (≈3 to 4 servings/wk) to minimize exposure to methylmercury.117 The FDA has concluded that persons other than pregnant women and women who may become pregnant can consume up to 7 ounces per week of fish with methylmercury levels around 1 ppm (eg, shark, swordfish, king mackerel, tilefish) and 14 ounces per week of fish with mercury levels averaging 0.5 ppm (eg, fresh tuna, orange roughy, marlin, red snapper).118 In July 2002, an FDA Scientific Committee advised the FDA to conduct a more detailed analysis of the contribution of methylmercury from tuna (with emphasis on large tuna consumed as steaks rather than canned tuna) to total methylmercury levels in women and children. Although more data are needed, information currently available about the methylmercury content of selected fish can be found on the FDA web site.119
In summary, consumers need to be aware of both the benefits and risks of fish consumption for their particular stage of life. Children and pregnant and lactating women may be at increased risk for mercury intoxication from fish consumption but also are at low risk for CHD. Thus, avoidance of potentially contaminated fish is a higher priority for this group. For middle-aged and older men and postmenopausal women, the benefits of fish consumption far outweigh the risks within the guidelines established by the FDA and Environmental Protection Agency. Consumption of a wide variety of species within the guidelines is the best approach to both minimizing mercury exposure and increasing omega-3 fatty acid intake.
Previous Section
Next Section
Summary
Omega-3 fatty acids have been shown in epidemiological and clinical trials to reduce the incidence of CVD. Large-scale epidemiological studies suggest that individuals at risk for CHD benefit from the consumption of plant- and marine-derived omega-3 fatty acids, although the ideal intakes presently are unclear. Evidence from prospective secondary prevention studies suggests that EPA+DHA supplementation ranging from 0.5 to 1.8 g/d (either as fatty fish or supplements) significantly reduces subsequent cardiac and all-cause mortality. For α-linolenic acid, total intakes of ≈1.5 to 3 g/d seem to be beneficial.
Collectively, these data are supportive of the recommendation made by the AHA Dietary Guidelines to include at least two servings of fish per week (particularly fatty fish). In addition, the data support inclusion of vegetable oils (eg, soybean, canola, walnut, flaxseed) and food sources (eg, walnuts, flaxseeds) high in α-linolenic acid in a healthy diet for the general population (Table 5). The fish recommendation must be balanced with concerns about environmental pollutants, in particular PCB and methylmercury, described in state and federal advisories. Consumption of a variety of fish is recommended to minimize any potentially adverse effects due to environmental pollutants and, at the same time, achieve desired CVD health outcomes.
View this table:
In this window In a new window
TABLE 5. Summary of Recommendations for Omega-3 Fatty Acid Intake
RCTs have demonstrated that omega-3 fatty acid supplements can reduce cardiac events (eg, death, nonfatal MI, nonfatal stroke) and decrease progression of atherosclerosis in coronary patients. However, additional studies are needed to confirm and further define the health benefits of omega-3 fatty acid supplements for both primary and secondary prevention. For example, placebo-controlled, double-blind RCTs are needed to document both the safety and efficacy of omega-3 fatty acid supplements in both high-risk patients (eg, patients with type 2 diabetes, dyslipidemia, and hypertension, and smokers) and coronary patients on drug therapy. Mechanistic studies on their apparent effects on sudden death are also needed.
A dietary (ie, food-based) approach to increasing omega-3 fatty acid intake is preferable. Still, for patients with coronary artery disease, the dose of omega-3 (≈1 g/d) may be greater than what can readily be achieved through diet alone (Table 5). These individuals, in consultation with their physician, could consider supplements for CHD risk reduction. Supplements also could be a component of the medical management of hypertriglyceridemia, a setting in which even larger doses (2 to 4 g/d) are required (Table 5). The availability of high-quality omega-3 fatty acid supplements, free of contaminants, is an important prerequisite to their extensive use.
No comments:
Post a Comment