Millions of Americans take fish oil and vitamin D because of claims that these supplements may reduce the risk of heart disease and cancer.
But new research is suggesting otherwise.
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"We have a very good, very big study that says neither vitamin D, nor fish oil, reduce the risk of cancer or heart disease," said Steven Nissen, M.D., chairman of Cleveland Clinic’s Heart and Vascular Institute, who did not take part in the research.
Researchers studied 25,871 men and women age 50 and older for about five years.
Study participants were split into four groups. One group took 2,000 international units of vitamin D plus 1 gram of fish oil daily.
Another group took vitamin D only; while another took fish oil only.
The final quarter of participants did not take anything.
The primary goal of the study was to see if the supplements impacted the risk of developing cancer or heart disease.
Overall, results show vitamin D and fish oil were not effective in preventing cancer or heart disease.
"The good news is that both the fish oil and the vitamin D were safe -- there was no harm -- but there was also no benefit," said Dr. Nissen. "Therefore, our advice to people would be not to routinely take either unless there’s a very good other reason to take these supplements."
The study was funded by the National Institutes of Health.
Complete results can be found in The New England Journal of Medicine.