April 24, 2013
Multivitamin products are the largest consumed supplements in America. Expectations of daily consumption include:
- Combat micronutrient deficiencies
- Reduce risk for cardiovascular disease and other chronic diseases
- Reduce risk for cancer
- Increase life span
- Prevent infections
Is there really any evidence to suggest such benefits?
Three meta-analytical studies (study #1, study #2, study #3) came to the same general conclusion that insufficient evidence exists to suggest that supplementing with multivitamins (MVs) provides any benefit. The first one reviewed whether there was any effect on chronic diseases, stating that with the exception of malnourished individuals, no benefit is derived from MVs. The second analysis searched for a link to reduced risk of cancer and chronic diseases, concluding that no such evidence exists. The third study looked at whether MVs were observed to prevent infections in elderly people and was unable to make such a conclusion.
Here is a huge cohort study of over one million adult Americans, which concluded that MVs had no impact on mortality. A minimal connection was seen with reducing cancer, but not with cardiovascular disease. Evidence also showed that male smokers that supplemented with MVs had a significant increased risk for lung cancer. Another study which looked at MVs and its connection to lung cancer concluded that people would be better off if they were steered away from MVs.
Lastly, here is another large cohort study, which specifically looked at the relationship between MVs and the risk for cancer, cardiovascular disease, and mortality in over 160,000 postmenopausal women. “After a median follow-up of 8.0 and 7.9 years in the clinical trial and observational study cohorts, respectively, the Women's Health Initiative study provided convincing evidence that multivitamin use has little or no influence on the risk of common cancers, CVD, or total mortality in postmenopausal women.”
Have Multivitamins Been Shown to be Harmful?
Here is a meta-analytical study which looked at the relationship between high doses of Vitamin E and all-cause mortality. Its findings were that doses equal to or exceeding 400 IU/day may increase all-cause mortality. Another important meta-analysis concluded that supplementing with beta-carotene, vitamin A, and Vitamin E may increase mortality.
A randomized 10-year clinical trial investigated whether folic acid could increase the risk of prostate cancer in men. Their findings were that supplementation of folic acid was linked to an increased risk of prostate cancer, but interestingly folic acid through natural consumption was not.
Another combined analysis of 2 randomized double-blind controlled studies concluded that with a daily supplementation of 800 mcg folic acid in combination with B12 was associated with cancer and all-cause mortality in heart disease patients.
If you decide that you want to supplement with MVs based on a “better safe than sorry” factor, you should pay attention to the label attached to your brand. Doses of 800 mcg folic acid are clearly seen to be hazardous. Higher doses of Vitamin E and beta-carotene are also something to watch out for. Many brands carry these micronutrients in high amounts. Overall, there hardly exists a reason to use MVs. Consumption of micronutrients through natural sources should always be your goal.