November 16, 2018 — Nearly 19 million Americans take fish oil supplements and some 37 percent of us take vitamin D. Many may be motivated by research that has suggested these pills can protect heart health and prevent cancer. On Saturday, NPR published a story on long-awaited research on both supplements that called those claims into question.
The findings of the trial, called VITAL, were complex. When researchers looked at cancer and overall cardiovascular events, they found no protective benefit from taking vitamin D or fish oil supplements. But when they looked only at heart attacks, they did find a benefit, especially for African-Americans and people who eat little fish. (Researchers say further study is needed to see whether those benefits hold up.)
The story prompted a wave of questions from our readers and listeners. Many of you wrote in asking, essentially, should I stop taking these supplements?
To get answers to some of your questions, we spoke with Dr. JoAnn Manson, chief of the Division of Preventive Medicine, Department of Medicine, at Brigham and Women’s Hospital, who headed the VITAL trial. We also turned to Dr. Bess Dawson-Hughes, senior scientist and director of the Bone Metabolism Laboratory at Tufts University School of Medicine.
The findings of the VITAL study cast doubt on benefits of fish oil for cancer and cardiovascular disease. Should people just throw out their pills?
JoAnn Manson: No. For those already taking supplements, our findings do not offer a clear reason to stop. If you want to consider starting, our recommendation is to talk with your health care provider, but this does not need to be done on an urgent basis. We do caution against taking very high doses, but at the level fish oil [was taken] in our study there were no significant adverse effects. In addition, while fish oil did not reduce the risk of stroke or other cardiovascular problems, it did reduce the risk of heart attack by 28 percent and that is a significant finding.
Previous research suggests fish oil may have greater benefits for heart health than for reducing stroke, because there are some mechanisms — such as reducing irregular heart rhythm — which would be more important for heart attack than for stroke.