Vitamin D supplementation and lipid profile: what does the best available evidence show?

Vitamin D supplements have increasingly been used for the treatment and prevention of osteoporosis. Historically, effects of the vitamin on the cardiovascular (CV) system have been proposed and demonstrated in the literature, including benefits on serum lipids. Although observational studies support an association between increased serum vitamin D levels and a favorable lipid profile, interventional studies have shown no effects. This review presents and analyzes all the related randomized controlled trials (RCTs) identified in the literature from 1987 to present. A systematic literature search was conducted via MEDLINE, Cochrane Library and EMBASE and, out of 19 relevant RCTs identified, only one reported benefits of vitamin D supplementation on lipid profile parameters, while the rest showed no effects or even adverse outcomes, which are highlighted by the only meta-analysis in the field. Attempts to explain the paradox of beneficial findings of observational studies versus discouraging results of interventional studies have been made and the most popular suggests that high serum vitamin D concentrations may not be the cause of good health but its outcome instead, as healthy people are more likely to stay outdoors longer and have better eating habits. For definitive answers to be given, large, well-designed RCTs need to be conducted that will take into account and adjust for dietary consumption as well as serum calcium and parathyroid hormone levels, both of which have been shown to be associated with the CV system. Until then, recommendations for vitamin D supplementation should not change.