Omega-3 Fatty Acids: An Essential Contribution
The human body can make most of the types of fats it needs from other fats or raw materials. That isn’t the case for omega-3 fatty acids (also called omega-3 fats and n-3 fats). These are essential fats—the body can’t make them from scratch but must get them from food. Foods high in Omega-3 include fish, vegetable oils, nuts (especially walnuts), flax seeds, flaxseed oil, and leafy vegetables.
What makes omega-3 fats special? They are an integral part of cell membranes throughout the body and affect the function of the cell receptors in these membranes. They provide the starting point for making hormones that regulate blood clotting, contraction and relaxation of artery walls, and inflammation. They also bind to receptors in cells that regulate genetic function. Likely due to these effects, omega-3 fats have been shown to help prevent heart disease and stroke, may help control lupus, eczema, and rheumatoid arthritis, and may play protective roles in cancer and other conditions.
Omega-3 fats are a key family of polyunsaturated fats. There are three main omega-3s:
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) come mainly from fish, so they are sometimes called marine omega-3s.
Alpha-linolenic acid (ALA), the most common omega-3 fatty acid in most Western diets, is found in vegetable oils and nuts (especially walnuts), flax seeds and flaxseed oil, leafy vegetables, and some animal fat, especially in grass-fed animals. The human body generally uses ALA for energy, and conversion into EPA and DHA is very limited.
The strongest evidence for a beneficial effect of omega-3 fats has to do with heart disease. These fats appear to help the heart beat at a steady clip and not veer into a dangerous or potentially fatal erratic rhythm. (1) Such arrhythmias cause most of the 500,000-plus cardiac deaths that occur each year in the United States. Omega-3 fats also lower blood pressure and heart rate, improve blood vessel function, and, at higher doses, lower triglycerides and may ease inflammation, which plays a role in the development of atherosclerosis. (1)
Several large trials have evaluated the effect of fish or fish oils on heart disease. In the Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardio (known as the GISSI Prevention Trial), heart attack survivors who took a 1-gram capsule of omega-3 fats every day for three years were less likely to have a repeat heart attack, stroke, or die of sudden death than those who took a placebo. (2) Notably, the risk of sudden cardiac death was reduced by about 50 percent. In the more recent Japan EPA Lipid Intervention Study (JELIS), participants who took EPA plus a cholesterol-lowering statin were less likely to have a major coronary event (sudden cardiac death, fatal or nonfatal heart attack, unstable angina, or a procedure to open or bypass a narrowed or blocked coronary artery) than those who took a statin alone. (3)
Most Americans take in far more of another essential fat—omega-6 fats—than they do omega-3 fats. Some experts have raised the hypothesis that this higher intake of omega-6 fats could pose problems, cardiovascular and otherwise, but this has not been supported by evidence in humans. (4) In the Health Professionals Follow-up Study, for example, the ratio of omega-6 to omega-3 fats wasn’t linked with risk of heart disease because both of these were beneficial. (5) Many other studies and trials in humans also support cardiovascular benefits of omega-6 fats. Although there is no question that many Americans could benefit from increasing their intake of omega-3 fats, there is evidence that omega-6 fats also positively influence cardiovascular risk factors and reduce heart disease.
Researchers are taking a hard look at a different sort of balance, this one between possible effects of marine and plant omega-3 fats on prostate cancer. Results from the Health Professionals Follow-up Study and others show that men whose diets are rich in EPA and DHA (mainly from fish and seafood) are less likely to develop advanced prostate cancer than those with low intake of EPA and DHA. (6) At the same time, some-but not all-studies show an increase in prostate cancer and advanced prostate cancer among men with high intakes of ALA (mainly from supplements). However, this effect is inconsistent. In the very large Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, for example, there was no link between ALA intake and early, late, or advanced prostate cancer. (7)
Recipes for health
Here’s a delicious way to get your omega-3s: Try Pan Roasted Salmon with Minty Snap Peas.
Given the wide-ranging importance and benefits of marine omega-3 fatty acids, it is important to eat fish or other seafood one to two times per week, particularly fatty (dark meat) fish that are richer in EPA and DHA. This is especially important for women who are pregnant or hoping to become pregnant and nursing mothers. From the third trimester until the second year of life, a developing child needs a steady supply of DHA to form the brain and other parts of the nervous system. Many women shy away from eating fish because of concerns that mercury and other possible contaminants might harm their babies, (9) yet the evidence for harm from lack of omega-3 fats is far more consistent, and a balance of benefit vs. risk is easily obtained. (To learn more about the controversy over contaminants in fatty fish, read Fish: Friend or Foe.)
This table lists common fish and seafood products and their omega-3 fatty acid content.
Type of Seafood Serving Size Omega-3 Fatty Acids (mg/serving) Anchovy 2.0 oz 1,200 Catfish (farmed) 5.0 oz 253 Clams 3.0 oz 241 Cod (Atlantic) 6.3 oz 284 Crab 3.0 oz 351 Fish sticks (frozen) 3.2 oz 193 Halibut 5.6 oz 740 Lobster 3.0 oz 71 Mahi mahi 5.6 oz 221 Mussels 3.0 oz 665 Oysters 3.0 oz 585 Pollock (Alaskan) 2.1 oz 281 Salmon (wild) 6.0 oz 1,774 Salmon (farmed) 6.0 oz 4,504 Sardines 2.0 oz 556 Scallops 3.0 oz 310 Shrimp 3.0 oz 267 Swordfish* 3.7 oz 868 Trout 2.2 oz 581 Tuna (albacore)** 3.0 oz 733 Tuna (light, skipjack) 3.0 oz 228
SOURCE: Mozaffarian D, Rimm EB. JAMA. 2006;296:1885-1899.
*Swordfish contains high levels of mercury, as does shark, king mackerel, and tilefish (sometimes called golden bass or golden snapper). Women who are or may become pregnant, nursing mothers, and young children should avoid these high-mercury species of fish, but can eat up to 12 ounces (two average meals) a week of a variety of fish and shellfish that are lower in mercury.
**Albacore tuna contains more mercury than canned, light tuna. Women who are or may become pregnant, nursing mothers, and young children should limit albacore tuna to one serving per week.
References
1. Leaf A. Prevention of sudden cardiac death by n-3 polyunsaturated fatty acids. J Cardiovasc Med. (Hagerstown). 2007; 8 Suppl 1:S27-29.
2. Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto miocardico. Lancet. 1999; 354:447-55.
3. Yokoyama M, Origasa H, Matsuzaki M, et al. Effects of eicosapentaenoic acid on major coronary events in hypercholesterolaemic patients (JELIS): a randomised open-label, blinded endpoint analysis. Lancet. 2007; 369:1090-98.
4. Willett WC. The role of dietary n-6 fatty acids in the prevention of cardiovascular disease. J Cardiovasc Med. (Hagerstown). 2007; 8 Suppl 1:S42-5.
5. Mozaffarian D, Ascherio A, Hu FB, et al. Interplay between different polyunsaturated fatty acids and risk of coronary heart disease in men. Circulation. 2005; 111:157-64.
6. Leitzmann MF, Stampfer MJ, Michaud DS, et al. Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer. Am J Clin Nutr. 2004; 80:204-16.
7. Koralek DO, Peters U, Andriole G, et al. A prospective study of dietary alpha-linolenic acid and the risk of prostate cancer (United States). Cancer Causes Control. 2006; 17:783-91.
8. Eilander A, Hundscheid DC, Osendarp SJ, Transler C, Zock PL. Effects of n-3 long chain polyunsaturated fatty acid supplementation on visual and cognitive development throughout childhood: a review of human studies. Prostaglandins Leukot Essent Fatty Acids. 2007; 76:189-203.
9. Oken E, Kleinman KP, Berland WE, Simon SR, Rich-Edwards JW, Gillman MW. Decline in fish consumption among pregnant women after a national mercury advisory. Obstet Gynecol. 2003; 102:346-51.
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Omega-3 Fatty Acids: Foods & Benefits
The Power of Fish
What are omega-3 fatty acids?
Omega-3 fatty acids are a type of fat the body cannot make on its own. They are an essential fat, which means they are needed to survive. We get the omega-3 fatty acids we need from the foods we eat.
What are the best sources of omega-3 fatty acids?
Fish are the best food source of omega-3 fatty acids. Some plants also contain omega-3 fatty acids.
What do EPA, DHA and ALA mean?
There are two kinds of omega-3 fatty acids in fish — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The form of omega-3 in plants is called alpha-linolenic (ALA).
How do omega-3 Fatty Acids help improve my health?
Research shows that omega-3 fatty acids can improve your cardiovascular health. Most of this research involves EPA + DHA, but ALA can also help improve your health. Benefits of including omega-3 fatty acids in your diet include:
Reduced risk of cardiovascular disease.
Reduced risk of death if you have cardiovascular disease.
Reduced risk of sudden cardiac death caused by an abnormal heart rhythm.
Reduced risk of blood clots because omega-3 fatty acids help prevent blood platelets from clumping together.
Keeping the lining of the arteries smooth and free of damage that can lead to thick, hard arteries. This helps keep plaque from forming in the arteries.
Lowering triglyceride levels by slowing the rate they form in the liver. High levels of triglycerides in the blood increase the risk of heart disease.
Less inflammation. Atherosclerosis (hardening of the arteries) is thought to involve your body's inflammatory response. Omega-3 fatty acids slow production of substances that are released during the inflammatory response.
Omega-3 fatty acids may also:
Raise levels of high-density lipoprotein (HDL/“good” cholesterol).
Lower blood pressure. People who eat fish tend to have lower blood pressure than those who don’t.
Amount of Omega-3 Fatty Acids in Selected Fish and Seafood
Mackerel Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 2.5–2.6 grams
Salmon (wild) Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 1.8 grams
Herring Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 1.3–2 grams
Tuna (Bluefin) Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 1.2 grams
Lake Trout Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 2 grams
Anchovy Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 1.4 grams
Tuna (Albacore)* Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 1.5 grams
Lake White fish (freshwater) Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 1.5 grams
Bluefish Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 1.2 grams
Halibut Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 0.9 grams
Striped Bass Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 0.8 grams
Sea Bass (mixed species) Serving Size: 3 ounces (100 grams) Amount of Omega-3 Fat: 0.65 grams
Tuna, white meat canned Serving Size: 3 ounces drained Amount of Omega-3 Fat: 0.5 grams
*Contains high level of Mercury. Limit amount you eat.
Source: USDA Food Composition Databases
How much Omega-3 do I need?
The American Heart Association recommends that patients who do not have a history of heart disease eat at least 2 servings of fish each week (a total of 6-8 ounces). This should include a variety of fish. Cold-water wild varieties of fish like mackerel, tuna, salmon, sardines and herring contain high amounts of omega-3 fatty acids. See the list above to help choose fish with high levels of omega-3 fatty acids.
If you have heart disease, your healthcare professional may recommend that you have one gram of EPA +DHA every day. If you have trouble getting this amount through food alone, talk to your doctor about taking a fish oil supplement.
If you have high triglyceride levels, you may need to eat more foods that are good sources of omega-3 fatty acids, even if you take medication to lower your triglyceride levels. Your healthcare provider may also want you to take a fish oil supplement. In general, 2-4 grams of EPA + DHA every day is recommended for patients with high triglyceride levels. This amount has been shown to lower triglyceride levels 25 to 35 percent.
Can you have too many omega-3 fatty acids?
Talk to your healthcare provider if you have 3 grams or more of omega-3 fatty acids in your diet each day. High levels of these essential fatty acids can cause bleeding.
Should I be concerned about mercury in fish?
Mercury occurs naturally in the environment and as a result of industrial pollution. It falls from the air and can collect in streams and oceans, where it is converted into methylmercury. Too much methylmercury can be harmful. This is especially true for unborn and young children.
Some fish have higher levels of mercury than others. These include shark, swordfish, tilefish, and King mackerel. Everyone should limit the amounts of these fish in their diet. Women who are pregnant or nursing and young children should not eat these types of fish. Women who are pregnant or nursing can safely eat 12 ounces of other types of fish each week. These include shellfish, canned fish and smaller fish.
Albacore Tuna has more mercury than canned light tuna. Limit the amount of albacore tuna you eat to 6 ounces per week.
What if I’m allergic to fish or don’t want to eat fish?
Fish is the best food source of omega-3 fatty acids, but several plants contain ALA. This is not as rich of a source of omega-3 fatty acids, but some studies show that ALA can reduce the risk of cardiovascular disease.
Good sources of ALA are ground or milled flaxseeds, flaxseed oil, chia seeds, walnuts, soy foods and canola oil. Another source of ALA is algae or algae oil, which is broken down to DHA. Many foods that are fortified with omega-3 use algae oil. These are excellent options for vegetarians that do not eat fish.
There are currently no serving size recommendations for ALA-rich foods. But, adding these foods to your diet regularly may help your heart health.
What are Omega-3 Fatty Acids
Research shows that eating two 4-ounce servings of seafood per week may reduce the risk of heart disease and related deaths. Many health professionals attribute this potentially life-saving quality of seafood to the presence of omega-3 essential fatty acids. And, omega-3s are not limited to fish and seafood. They are also found in some vegetable oils, nuts, seeds and soy foods.
Fish contain two important omega-3 fatty acids: EPA (eicosapetaenoic acid) and DHA (docosahexaeonic acid). Research suggests people who eat fatty fish and other seafood as part of a healthy dietary pattern have lower risk of heart problems and lower risks of chronic disease. This has been seen in individuals with and without a history of heart disease, though evidence is stronger for the benefits of omega-3 fatty acids in people with a history of heart disease. For instance, if you have high blood triglycerides, consuming omega-3 fatty acids may help lower your levels.
Plant-Based Omega-3s
Some plants also contain an omega-3 fatty acid known as ALA (alpha-linolenic acid). You can find it in various oils, nuts, seeds, beans and other sources. Here are tips for getting more plant-based omega-3s:
Include oils that contain omega-3 fatty acids, such as flaxseed oil, walnut oil, canola oil or soybean oil.
Add hemp hearts or ground flaxseed to cereals, yogurt and salads. The body isn't able to break down whole flaxseeds but grinding them before use helps with absorption.
Substitute ground flaxseed for part of the butter or oil when baking. Use 3 tablespoons of ground flaxseed mixed with 1 tablespoon of water to replace 1 tablespoon of oil.
Snack on edamame or walnuts for a snack that provides omega-3 fatty acids.
Omega-3 Supplements
Omega-3 supplements may be beneficial in combating heart disease though recent studies have challenged if taking supplements is as effective as consuming food sources. Scientific evidence describing the advantage of omega-3 supplements on heart disease risk for people who don't actually have heart disease is also limited. Consult a health professional to determine if you would benefit from an omega-3 supplement.
Too Much Omega-3?
Given the fact that many of our foods are fortified with omega-3 fatty acids, it is possible to get excess amounts of it if you take additional supplements. The U.S. Food and Drug Administration advises consuming no more than 3 grams of EPA and DHA omega-3 fatty acids per day from foods and dietary supplements, unless prescribed by a healthcare provider. Taking too much may cause uncomfortable gastrointestinal symptoms. And, although small, there is a risk of increased bleeding possible when people who take anti-platelet agents or anticoagulants also take high doses of omega-3 fatty acids.
The omega-3 fatty acid content of fish varies. Higher amounts are typically found from sources such as herring, salmon, sardines and trout. Mackerel is also a rich source of omega-3 fatty acids, however, one variety known as king mackerel is also high in mercury and the FDA advises individuals who are pregnant or nursing and young children to avoid this fish. Atlantic mackerel and Pacific chub mackerel are both lower mercury alternatives.
In summary, remember to feast on fish at least twice a week and regularly include omega-3-rich plant sources, such as flaxseeds, chia seeds and walnuts.
Finally, ask your doctor or a registered dietitian nutritionist to determine if an omega-3 fatty acid supplement would be helpful for you. Omega-3 fatty acid supplements should not be taken without a physician's supervision.
