March 2014 Issue

Omega-3 Supplementation — Help Clients Sort Through the Fish Oil Facts
By Linda Antinoro, JD, RD, LDN, CDE
Today’s Dietitian
Vol. 16 No. 3 P. 52

Despite recent published reports suggesting that omega-3 supplements lack the cardiovascular health benefits they once claimed and could be associated with various health risks, many people continue to use them. According to the 2014 survey of 10,000 supplement users, fish/marine oil supplements still were popular, with 67.2% of respondents using them.

This consumption may not be bad. Research on omega-3s suggests that these supplements may be useful and even necessary for people with very high triglyceride levels, pregnant and nursing women, and individuals who have difficulty eating oily fish twice per week.

Cardiovascular Connection
Previous clinical trials of fish oil supplements often have associated omega-3 supplementation with heart health benefits. The GISSI Prevenzione study, for example, published in the August 1999 issue of the Lancet, followed 1,324 patients and found that the group who received a 1-g dose of an omega-3 supplement each day for 3 1/2 years significantly reduced the risk of death, nonfatal myocardial infarction, and nonfatal stroke among those who had survived a recent myocardial infarction.1 Fast-forward to a 2013 study involving more than 12,000 patients at high risk of a heart attack who were randomized to receive either 1,000 mg of fish oil per day or a placebo.2 After five years, there was no reduction in cardiovascular mortality and morbidity.

A meta-analysis of 20 studies published in the September 2012 issue of The Journal of the American Medical Association supports a similar conclusion. Patients who received an average dose of 1.51 g of omega-3 supplements per day for a median treatment duration of two years didn’t experience a lower risk of myocardial infarction, stroke, cardiac death, sudden death, or all-cause mortality.3 However, Dariush Mozaffarian, MD, DrPH, a cardiologist and epidemiologist at Harvard Medical School, points out that the other research did find that omega-3s lowered the risk of cardiac death by 10%.

A possible reason for the seemingly contradictory results between the earlier and more recent studies on omega-3 supplementation, according to researchers, is that most of the later trials involve people with established heart disease who already are being treated with various medications, such as antihypertensives, antiarrhythmics, and statins.4 For example, in the GISSI trial, only 5% of patients received statins at baseline. Patients already using cardioprotective agents may not experience further benefits when given omega-3 supplements since drug therapy can mimic or mask the actions of omega-3 supplements by lowering blood pressure, blood lipid levels, or inflammation.4

Plus, what’s unknown at this time is whether omega-3 supplements will help thwart cardiac problems in healthy people or those at low risk of heart disease. The Vitamin D and Omega-3 Trial (VITAL), an ongoing study of 20,000 men and women investigating whether taking daily supplements of vitamin D3 (2,000 IU) or omega-3s (1 g) lowers the risk of developing cancer, heart disease, and stroke in people who don’t have a prior history of these illnesses, hopes to answer this question.

One consistent benefit demonstrated by research on omega-3 supplements is that they can improve hypertriglyceridemia. The American Heart Association endorses 2 to 4 g of EPA and DHA per day in capsule form under a physician’s supervision for those individuals who need to lower their triglyceride levels. Even modest doses work to some degree. In one study, triglyceride levels dropped 14.5 mg/dL more in patients who took a 1-g capsule containing 465 mg of EPA and 375 mg of DHA compared with those who received a placebo.5 Though triglyceride reduction didn’t decrease the rate of cardiovascular events in this study, lowering triglycerides still is a worthwhile goal because extremely elevated triglycerides can contribute to pancreatitis.4

Prostate Cancer
A study published in the August 2013 issue of the Journal of the National Cancer Institute examined the association between blood levels of omega-3 fatty acids and prostate cancer risk among men who participated in the Selenium and Vitamin E Cancer Prevention Trial (SELECT). The researchers found that men who had higher blood levels of omega-3 fatty acids were more likely to develop prostate cancer.6 Many headlines followed, erroneously singling out fish oil supplements as the culprit.

According to Theodore Brasky, PhD, the lead researcher of the study, “Only a minority of the men in the study took supplements.” While researchers saw a correlation and not a cause-and-effect relationship, it still may be prudent for men to avoid large doses of omega-3s whether from excessive fatty fish intake or supplements, he says.

Conversely, a study published in the January issue of Cancer Prevention Research found that men with prostate cancer who ate a low-fat diet and took fish oil supplements had lower levels of serum proinflammatory eicosanoids and a lower cell cycle progression score—a measurement used to predict cancer recurrence—than men who ate a typical Western diet.7 Subjects received 5 g of fish oil per day consisting of five 1-g capsules each containing 200 mg of EPA and 367 mg of DHA.

The researchers acknowledge that they couldn’t determine whether either treatment alone would have produced the same results. They combined the two interventions based on preclinical trials that showed a decrease in the development and progression of prostate cancer associated with reducing the ratio of omega-6 to omega-3 fatty acids and lowering dietary fat intake.

Pregnancy and Postpartum
Omega-3 supplementation also has been found to benefit the health of infants and pregnant women. Omega-3s assist in the normal development and functioning of the brain and retinas in fetuses and infants.

According to the International Society for the Study of Fatty Acids and Lipids, pregnant and lactating women need 300 mg of DHA per day.8 Research shows that 200 to 300 mg of omega-3 fatty acids per day, particularly DHA, is associated with improved infant health outcomes such as visual and cognitive development.

It’s been suggested that nursing mothers should take 200 to 300 mg of omega-3 fatty acids so the nutrients can pass through breast milk to their babies. Dietitians can encourage pregnant women to eat fish low in mercury, such as salmon and sardines, as well as DHA-fortified foods. But if clients don’t eat enough or choose to avoid these foods, omega-3 supplements are an option.

Optimal Omega-3 Doses
Most medical experts and health organizations recommend individuals get 250 to 500 mg of EPA and DHA per day, first from fatty fish and then from supplements. According to the 2010 Dietary Guidelines, the mean intake of seafood in the United States is approximately 3 1/2 oz per week. Increasing intake to 8 oz per week provides an average consumption of 250 mg of EPA and DHA per day.

The American Heart Association agrees with this recommendation for healthy people who don’t have documented coronary heart disease (CHD), although it acknowledges that patients with CHD probably need closer to 1 g of EPA and DHA combined per day, and that this amount may require the addition of omega-3 supplementation. The association discourages exceeding 3 g/day from capsules unless under the guidance of a trained health care professional.

Bottom Line
When counseling clients about omega-3 intake, inform them that consumption is important because our bodies can’t make these essential fatty acids on their own. Tell them that they should obtain omega-3s through food first whenever possible. Explain that while plant-based omega-3s such as walnuts, chia seeds, and ground flax have alpha-linolenic acid and other nutritional merits, the body converts alpha-linolenic acid into EPA and DHA at rather low levels.

Finally, if clients have difficulty consuming enough omega-3s, give them guidance based on their health status to determine the correct dosage of omega-3 supplements they should take daily.

— Linda Antinoro, JD, RD, LDN, CDE, is a freelance writer and part of the Nutrition Consultation Service at Brigham and Women’s Hospital in Boston.


EPA and DHA Content in Fish


EPA (mg)

DHA (mg)

Combined Total (mg)*

Herring, Pacific, cooked




Anchovy, canned in oil




Salmon, sockeye, cooked




Mackerel, Atlantic, cooked




Trout, rainbow, wild, cooked




Sardines, Atlantic, canned in oil




Tuna, white, canned in water




* Amount for combined EPA and DHA listed from highest to lowest in milligrams per 4-oz serving
— Source:  USDA National Nutrient Database for Standard Release, Release 26


1. GISSI-Prevenzione Investigators (Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardico). Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Lancet. 1999;354(9177):447-455.

2. Risk and Prevention Study Collaborative Group. n-3 fatty acids in patients with multiple cardiovascular risk factors. N Engl J Med. 2013;368(19):1800-1808.

3. Rizos EC, Ntzani EE, Bika E, Kostapanos MS, Elisaf MS. Association between omega-3 fatty acid supplementation and risk of major cardiovascular disease events. A systematic review and meta-analysis. JAMA. 2012;308(10):1024-1033.

4. Kwak SM, Myung SK, Lee YU, Seo HG. Efficacy of omega-3 fatty acid supplements (eicosapentaenoic acid and docosahexaenoic acid) in the secondary prevention of cardiovascular disease: a meta-analysis of randomized, double-blind, placebo-controlled trials. Arch Intern Med. 2012;172(9):686-694.

5. Origin Trial Investigators, Bosch J, Gerstein HC, et al. n-3 fatty acids and cardiovascular outcomes in patients with dysglycemia. N Engl J Med. 2012;367(4):309-318.

6. Brasky TM, Darke AK, Song X, et al. Plasma phospholipid fatty acids and prostate cancer risk in the SELECT Trial. J Natl Cancer Inst. 2013;105(15):1132-1141.

7. Galet C, Gollapudi K, Stepanian S, et al. Effect of a low-fat fish oil diet on proinflammatory eicosanoids and cell-cycle progression score in men undergoing radical prostatectomy. Cancer Prev Res (Phila). 2014;7(1):97-104.

8. Adequate intakes/recommendation table. International Society for the Study of Fatty Acids and Lipids website.