The 25,871 study participants were selected to represent the general U.S. population with a typical risk of developing cancer or heart disease. Participants in the study were randomly assigned to take fish oil supplements, vitamin D supplements, both supplements, or a placebo. After a median follow-up of 5.3 years, the researchers compared rates of cardiovascular events and invasive cancer in the study participants.
For omega-3 fatty acids, the trial found that people who took the supplements did not have lower incidence of major cardiovascular events or cancer, including prostate cancer. Overall, the same was true for patients who took vitamin D supplements. However, in an interview with Cancer Network, the study's lead author, JoAnn Manson, M.D., DrPH, noted that a sub-analysis of people who took Vitamin D supplements found a 25% reduction in cancer death, but not cancer incidence. This could be a result of vitamin D modifying the tumor biology to make it less likely to metastasize, as there is some evidence suggesting this is possible.
Other research has found conflicting results regarding fish oil supplements containing omega-3 fatty acids and prostate cancer. Previous QUEST articles have covered this. Visit the URF website at www.drcatalona.com and search "fish oil" for more information.
The VITAL study will continue to track patients in the coming years to follow any trends in the groups of patients. The authors anticipate publishing additional findings after a longer follow-up period that hopefully will provide clearer guidance for the use of these supplements.
N Engl J Med. 2019 Jan 3;380(1):23-32. doi: 10.1056/NEJMoa1811403. Epub 2018 Nov 10.