Fish oil capsules are among the most popular supplements sold, but recent studies have questioned the benefits and even proposed possible risks related to fish oil supplementation.

A study published in May in the New England Journal of Medicine followed subjects with cardiovascular risk factors, such as high blood pressure and cholesterol, but no history of heart attack. At the end of the five-year study period, 11.7 percent of the 6,244 patients taking a capsule containing one gram of fish oil daily had died or been hospitalized for heart problems, compared to 11.9 percent of the 6,269 volunteers who received one gram of olive oil every day as a placebo.

Then in July, a study published in the Journal of the National Cancer Institute found that daily fish oil supplements may be associated with a 43 percent increased risk for prostate cancer overall in men, and a 71 percent increased risk in aggressive prostate cancer.

Yet the omega-3 fatty acids found in fish oil have long been considered beneficial for their powerful anti-inflammatory effects. “We know that a major factor in heart disease is a low-grade, chronic inflammation throughout the body,” explains Dr. Ted Weiss, assistant professor of nutrition and dietetics at Saint Louis University. “This is known to be involved in the development of plaques in the arteries. Fish oil’s anti-inflammatory properties may help counteract the effects of this systemic inflammation.” Weiss notes that fish oil’s omega-3 fatty acids also can help lower triglycerides in the blood, which increase cardiovascular risk; help prevent clotting; and prevent irregular heart rhythms.

However, Weiss is a proponent of consuming those beneficial omega-3s from whole foods, not from capsules. “In nature, things work out well and tend to come in packages where there are cooperative effects among nutrients or compounds in foods,” he says. Some of these ‘package deals’ in whole foods are understood, but Weiss thinks there is much to learn about how foods work to help or harm our health.

For example, Weiss notes that many vegetables contain nitrates, which when isolated have been found to be carcinogenic. However, vegetables are thought to help protect the body from cancer. He also cautions that the unregulated supplement industry may not be selling products that are as pure and potent as the label claims.

Dr. Mark Friedman, a cardiologist with SSM Heart Institute at St. Mary’s Health Center, agrees that omega-3 fatty acids consumed from oily fish, such as tuna, salmon and mackerel, is better than supplementation. “There’s a tremendous amount of data showing the benefits of the Mediterranean diet, which includes high fish intake, healthy oils, healthy nuts, fruits and vegetables,” he says. “And most of the benefits for fish oil seem to be at these lower doses of eating a 3-ounce serving of fish two to three times a week. Have tuna twice a week for lunch and salmon once for dinner, and you’ve got your fish for the week.”

Other sources of omega-3 fatty acids are ground flaxseeds and walnuts, both of which can be added to salads, yogurt or cereal.

Weiss and Friedman agree that fish oil capsules may be an alternative for people who can’t eat fish, and Friedman recommends 1,000 milligrams per day. However, talk to your primary-care physician if you plan to take fish oil supplements, especially if you take aspirin or any other sort of blood thinner.

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