Taking fish oil supplements may not be effective in preventing cardiovascular disease and cancer, according to a new study. Cathy Scola / Getty Images Hide caption

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Cathy Scola / Getty Images

Taking fish oil supplements may not be effective in preventing cardiovascular disease and cancer, according to a new study.

Cathy Scola / Getty Images

Many people routinely take supplements like vitamin D and fish oil in hopes of fending off major killers like cancer and heart disease.

However, the evidence for the potential benefits of the supplements is mixed.

The long awaited government funded research has now produced some of the clearest evidence of the usefulness of taking the supplements. And the results – published in two articles – are mostly disappointing.

“Both studies were negative,” says Dr. Lawrence Fine, director of clinical application and prevention at the National Heart, Lung, and Blood Institute, part of the National Institutes of Health that funded the studies.

“Overall, they showed that neither fish oil nor vitamin D actually reduced the incidence of heart disease or cancer,” says Fine.

The results were presented at the American Heart Association’s scientific sessions in Chicago and published online on Saturday by the New England Journal of Medicine. One article was about vitamin D supplementation and the other was about fish oil.

Almost 26,000 healthy adults aged 50 and over without cancer or heart disease who participated in the VITAL research project took part in the studies. Twenty percent of the participants were African American.

Some of the participants took either 1 gram of fish oil – which contains omega-3 fatty acids – plus 2,000 international units of vitamin D daily. Others consumed the same dose of vitamin D plus a placebo, while others took the same dose of fish oil plus a placebo. The last group took two placebos. After more than five years, the researchers could not find any overall benefit.

While the overall results were disappointing, there seemed to be a positive effect when it came to one aspect of heart disease and fish oil: heart attacks.

A secondary analysis found that taking fish oil reduced the risk of heart attack by about 28 percent, which is a “statistically significant” finding, says Dr. JoAnn Manson, director of preventive medicine at Brigham and Women’s Hospital in Boston. She directed the research.

Those who seemed to benefit the most were people who didn’t typically eat a lot of fish in their daily diet, as well as African Americans, Manson says.

African Americans in the study had a 77 percent lower risk of heart attack than a placebo, which is a “dramatic reduction,” says Manson. More research is needed to confirm these results, she adds, but “In the meantime, it would be reasonable for African Americans to speak to their health care providers about whether they are candidates for taking fish oil supplements.”

In an editorial, also published in the New England Journal of Medicine, the authors introduce Dr. John F. Keaney and Dr. Clifford J. Rosen questioned some of the analyzes in the study, writing that the positive results about heart attacks and African Americans and those who do not eat a lot of fish need to be interpreted with caution.

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There were no serious side effects such as bleeding, high blood calcium levels, or gastrointestinal symptoms seen with either supplement.

Manson and her colleagues plan to further analyze their data and look for possible links between vitamin D and fish oil and cognitive function, autoimmune diseases, respiratory infections, and depression. Previous research suggests that the supplements may have some benefit for these conditions.

In the meantime, NIH official Lawrence Fine says, don’t throw away your fish oil and vitamin D.

“When thinking about a nutritional supplement, either omega-3s or vitamin D, talking to your doctor or health care provider is the next step,” says Fine.

Fine and Manson emphasized that vitamin D and the omega-3s in fish oil are important nutrients, but the best way to get them is by eating a balanced diet. This includes eating oily fish like sardines, tuna, and salmon, as well as cereals fortified with vitamin D, milk, and orange juice.

Another study presented at the same session looked at whether a substance derived from a component of fish oil known as icosapent ethyl could reduce adverse events in people who already had cardiovascular risk factors such as hardening of the arteries, diabetes, or high blood lipids are known as triglycerides.

Overall, this study found a 25 percent reduction in risk for patients taking the extract. These patients were less likely to die of heart disease, had a heart attack or stroke, were hospitalized for chest pain, or needed procedures like angioplasty, stenting, or bypass surgery, researchers reported.

“We report a remarkable level of risk reduction,” says Dr. Deepak Bhatt, who led the study and is a cardiologist at Brigham and Women’s Hospital.

The study, which was also a randomized clinical trial, tracked participants for an average of five years. The volunteers took icosapent ethyl, which is sold under the brand name Vascepa and developed by Amarin Corporation, which funded Bhatt’s research.

The product requires a prescription and is only available to patients with high triglycerides. However, the company is expected to file for FDA approval within the next year to expand treatment to all high-risk cardiovascular patients.

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