Vitamin D and fish oil show promise in prevention of cancer death and heart attacks

Nearly 26,000 U.S. men and women participated in the nationwide VITAL clinical trial. After more than five years of study and treatment, the results show promising signals for certain outcomes. For example, while Omega-3 fatty acids (fish oil) showed only a small, but nonsignificant, reduction in the primary cardiovascular endpoint of major CVD events, they were associated with significant reductions in heart attacks. The greatest treatment benefit was seen in people with dietary fish intake below the cohort median of 1.5 servings per week but not in those whose intake was above that level. In addition, African-Americans appeared to experience the greatest risk reductions. The heart health benefits are now confirmed by recent meta-analyses of omega-3 randomized trials.

Similarly, vitamin D supplementation did not reduce major CVD events or total cancer incidence but was associated with a statistically significant reduction in total cancer mortality among those in the trial at least two years. The effect of vitamin D in reducing cancer death is also confirmed by updated meta-analyses of vitamin D trials to date.

"The pattern of findings suggests a complex balance of benefits and risks for each intervention and points to the need for additional research to determine which individuals may be most likely to derive a net benefit from these supplements," says Dr. JoAnn Manson, lead author of the study from Brigham and Women's Hospital, an affiliate of Harvard Medical School.

"With heart disease and cancer representing the most significant health threats to women, it is imperative that we continue to study the viability of options that prevent these diseases and help women survive them," says Dr. Stephanie Faubion, NAMS medical director.