What is the benefit of fish oil capsules

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Harvard Health Blog

April 15, 2020

• By Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

The answer is more friend than foe, especially if the fish oil comes from food sources rather than supplements.

Omega-3s in balance

What’s so special about fish oil? It’s loaded with omega-3 fatty acids. These must come from food, since our bodies can’t make them.

The two-key omega-3 fatty acids are docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Fatty fish like salmon, mackerel, and sardines are rich in these omega-3s. Some plants are rich in another type of omega-3 fatty acid, alpha-linolenic acid, which the body can convert to DHA and EPA. Good sources of these are flaxseeds, chia seeds, walnuts, pumpkin seeds, and canola oil.

Omega-3 fatty acids play important roles in brain function, normal growth and development, and inflammation. Deficiencies have been linked to a variety of health problems, including cardiovascular disease, some cancers, mood disorders, arthritis, and more. But that doesn’t mean taking high doses translates to better health and disease prevention.

Fish oil supplements have been promoted as easy way to protect the heart, ease inflammation, improve mental health, and lengthen life. Such claims are one reason why Americans spend more than $1 billion a year on over-the-counter fish oil. And food companies are adding it to milk, yogurt, cereal, chocolate, cookies, juice, and hundreds of other foods.

But the evidence for improving heart health is mixed. In November 2018, a study reported in the New England Journal of Medicine found that omega-3 fatty acid supplements did nothing to reduce heart attacks, strokes, or deaths from heart disease in middle-age men and women without any known risk factors for heart disease. Earlier research reported in the same journal in 2013 also reported no benefit in people with risk factors for heart disease.

However, when researchers looked at subgroups of people who don’t eat any fish, the results suggested they may reduce their cardiovascular risk by taking a fish oil supplement.

Evidence linking fish oil and cancer has been all over the map. Most research, including the 2018 study cited above, has not shown any decreased risk of cancer. However, some earlier research suggested diets high in fatty fish or fish oil supplements might reduce the risk of certain cancers.

Take home message

How food, and its component molecules, affect the body is largely a mystery. That makes the use of supplements for anything other than treating a deficiency questionable.

Despite this one study, you should still consider eating fish and other seafood as a healthy strategy. If we could absolutely, positively say that the benefits of eating seafood comes entirely from omega-3 fats, then downing fish oil pills would be an alternative to eating fish. But it’s more than likely that you need the entire orchestra of fish fats, vitamins, minerals, and supporting molecules, rather than the lone notes of EPA and DHA.

The same holds true of other foods. Taking even a handful of supplements is no substitute for wealth of nutrients you get from eating fruits, vegetables, and whole grains.

What should you do if you currently take fish oil? If your doctor prescribed them—they are an approved and effective treatment for people with high blood triglyceride levels—follow his or her instructions until you can have a conversation about fish oil.

If you are taking them on your own because you believe they are good for you, it’s time to rethink that strategy. If you don’t eat fish or other seafood, you might benefit from a fish oil supplement. Also, you can get omega-3s from ground flaxseed or flaxseed oil, chia seeds, walnuts, canola oil, and soy oil. One to two servings per day can help you avoid a deficiency of omega-3s.

Following food author Michael Pollan’s simple advice about choosing a diet may be the best way forward: "Eat food. Not too much. Mainly plants."

Image: batteriesnotincluded/Getty Images

About the Author

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Howard LeWine, M.D., is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio

View all posts by Howard E. LeWine, MD

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No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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