Multivitamins apparently safe

A new Australian review claims that the use of dietary supplements does not increase the risk of death.

The meta-analysis included results of 21 randomized controlled trials investigating the efficacy and safety of supplementation with a combination of vitamins and minerals for an average of 43 months (at least one year) in a total of 91,074 participants, aged 62 years on average, without terminal diseases (1). The analysis showed that supplement intakes did not affect the risk of mortality due to cancer or vascular diseases. A
non-significant trend was shown for multivitamin/multimineral use and a reduced risk of all-cause mortality.

The researchers concluded that the results support the safety of supplements. They noted that the analyzed studies did not include participants who used multiple dietary supplements (e.g., two or more multivitamins or a multivitamin along with individual vitamins). Excessive long-term nutrient intake, exceeding the recom-mended daily intake values, may be harmful.

In the past, some meta-analyses have linked use of antioxidant supplement s (vitamin A, C and E and beta-carotene) to an increase in mortality risk: in 2007, a meta-analysis, which included 66 clinical trials, reported an increased risk of 16% (2). A critical expert analysis of the study showed that over 400 clinical trials repor-ting no deaths had been excluded. Following this criticism, the authors published corrections and a new meta-analysis, which still suggested a potential increase in mortality (3). A re-analysis of this meta-analysis found that while 36% of the trials included showed beneficial effects of supplements and 60% showed no efficacy, only 4% of the studies reported potentially harmful effects reflecting the safety of supplement use (4). A more recent observational study, which reported an increase in mortality risk by 2.4% (5) was criticized for serious weaknesses in planning, execution and evaluation.

1. Macpherson H. et al. Multivitamin-multimineral supplementation and mortality : a meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition. Published online January 2013.
2. Bjelakovic G. et al. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis. JAMA. 2007; 297(8):842-857.
3. Bjelakovic G. et al. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev. 2008; 16;(2):CD007176.
4. Biesalski H.-K. et al. Reexamination of a meta-analysis of the effect of antioxidant supplementation on mortality and health in randomized trials. Nutrients. 2010; 2(9):929-949.
5. Mursu J. et al. Dietary supplements and mortality rate in older women: the Iowa Women's Health Study. Arch Intern Med. 2011; 171(18):1625-1633.