Does the Evidence Support Dietary Supplements?

Abstract

Laurel Halloran, PhD, APRN When a patient arrives for an office visit, we do a medication reconciliation. What are they taking, and does it match our records? Often, we find that patients are taking various vitamins or supplements. There are more than 50,000 dietary supplements, and 55% of the adult population in the United States uses them. The industry is growing and in 2010 reached $28 billion in annual sales. But do patients really need supplements, and do they cause more harm than good? How should we be counseling our patients about this topic? Vitamin D supplementation is an open area of investigation. Clinical trials have been equivocal and sometimes contradictory. A study published in The Lancet Diabetes & Endocrinology analyzed 290 prospective observational studies and 172 randomized trials of vitamin D supplements. Observational studies indicated that high vitamin D levels reduced the risk of cardiovascular events by up to 58%, of diabetes by up to 38%, and of colorectal cancer by up to 34%. However, randomized trials did not confirm these benefits, and a meta-analysis of recent randomized trials did not show that vitamin D supplementation had any effect on disease occurrence, severity, or clinical course. The study researchers suggested that low vitamin D levels are a consequence of ill health, not a cause. In other research, low vitamin D levels were found to possibly be associated with depression. A study that reviewed 1 case-control study, 10 cross-sectional studies, and 3 cohort studies with a total of 31,424 participants was analyzed in 2013. Lower vitamin D levels were found in people with depression, and there was an increased odds ratio of depression for the lowest versus the highest vitamin D categories in the cross-sectional studies. The cohort studies showed a significantly increased hazard ratio of depression for the lowest versus the highest