3D coloured CT scan of patient with angina

A heart damaged by a heart attack. A large-scale trial found evidence that fish oil cuts heart-attack risk but vitamin D does not. Credit: K. H. Fung/SPL

Medical research

Massive trial shows limited value for popular supplements

No evidence found to indicate that vitamin D and fish oil fight cancer.

A large-scale trial has found no evidence that two popular supplements reduce the risk of cancer or the combined risk for a trio of cardiovascular problems.

JoAnn Manson at Brigham and Women’s Hospital in Boston, Massachusetts, and her colleagues recruited more than 25,000 healthy men and women in their fifties or older for a trial examining the effects of fish oil and vitamin D supplements. Some participants took both, others took only one type and the remaining participants took two placebos.

After an average of 5.3 years in the trial, participants who had taken fish oil had essentially the same likelihood of cancer as people who hadn’t. Compared with the placebo group, the fish-oil group had a lower rate of heart attack but the same rate of total cardiovascular events, a category that included heart attacks, strokes and death from cardiovascular disease.

Vitamin D supplements conferred no clear health benefits against cardiovascular disease or cancer, compared with a placebo.