News out of Seattle is sure to fuel confusion about fish oil supplements. Take this email I got yesterday from a friend. “Ok, I give up. Should I take them? Throw them away? June 29 — Fish oil may prevent breast cancer. Today (July 11) — Fish oil may increase risk of prostate cancer.”
First, the latest news. A study by scientists at the Fred Hutchinson Cancer Research Center in Seattle linked eating a lot of oily fish or taking potent fish oil supplements to a 43% increased risk for prostate cancer overall, and a 71% increased risk for aggressive prostate cancer. Their report was published online in the Journal of the National Cancer Institute.
They came to this conclusion by looking at blood samples of men taking part in the Selenium and Vitamin E Cancer Prevention Trial. (That trial, dubbed SELECT, found that selenium supplements did nothing to prevent prostate cancer, while vitamin E supplements slightly increased prostate cancer risk. Blood samples from men who had developed prostate cancer over the course of the trial had more omega-3 fats than those of men who didn’t develop prostate cancer.
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.
The report from the Fred Hutchinson researchers is just the latest to sound a warning about too much omega-3 fatty acids. In May 2013, for example, Italian researchers reported in the New England Journal of Medicine that omega-3 fatty acid supplements did nothing to reduce heart attacks, strokes, or deaths from heart disease in people with risk factors for heart disease.
This work follows similar warnings about vitamin E supplements, beta carotene supplements, and other high-dose dietary supplements.
Evidence linking fish oil and cancer has been all over the map. Some research suggests diets high in fatty fish or fish oil supplements might reduce the risk of certain cancers, including prostate cancer. Other research shows no such association.
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 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.
Experts will surely remain divided on their opinions about fish oil supplements for the general population. And don’t expect any clarity about what to do any time soon. I expect other studies with flip-flopping results in the future.
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.”