Huang H-Y et al. (2006) The efficacy and safety of multivitamin and mineral supplement use to prevent cancer and chronic disease in adults: a systematic review for a National Institutes of Health state-of-the-science conference. Ann Intern Med 145: 372–385

Published information on the safety and efficacy of multivitamin and mineral supplements is lacking, say the authors of a systematic review commissioned by the NIH for its State-of-the-Science conference.

Through a comprehensive and reproducible approach, the team identified 12 published articles from five randomized, controlled trials that examined the efficacy of multivitamin and mineral supplements in the primary prevention of cancer, cardiovascular disease, hypertension, cataracts, and age-related macular degeneration; not all chronic diseases the team aimed to analyze were represented in the literature. Safety was evaluated in eight articles (three case reports and published data from four randomized, controlled trials). The quality of all studies was rated 'fair', except for those looking at hypertension, which were rated 'poor'.

Overall conclusions were hard to draw, because of the heterogeneity of the studies. Results were also complicated by the studies' limitations, which included allowing participants to self-supplement with different formulations during a study, differences in baseline nutritional status of study populations, and relatively short follow-up times. While supplements are unlikely to have serious adverse effects, little evidence of their efficacy was seen, although some findings suggested a beneficial effect of supplementation in the primary prevention of cancer in patients with poor nutrient or antioxidant intake.