Vitamin D supplementation and health-related quality of life: a systematic review of the literature.

Vitamin D deficiency and insufficiency are highly prevalent worldwide and thought to potentiate a variety of chronic disease states, including diabetes, cancer, and depression. Routine vitamin D supplementation is often needed to meet vitamin D requirements. Little is known regarding the effect of vitamin D supplementation on quality of life. The purpose of this article was to systematically review the literature regarding quality-of-life outcomes from vitamin D supplementation in healthy and clinical populations. Clinical trials of vitamin D supplementation, where quality-of-life outcomes were reported, were selected from Medline and Web of Science databases. Inclusion criteria were English language articles available online (published between 1950 and May 2014), primary research articles, studies conducted on human beings, and treatment/supplementation with vitamin D. Articles were excluded if they involved topical vitamin D application or implicit cotreatment with other vitamins (eg, multivitamins). Articles selected for review were examined for process and methodologic quality using validated methodologies. A total of 15 articles met the inclusion criteria for review. Interventions were highly variable in terms of study population (eg, healthy/diseased, children/elderly, and baseline vitamin D status) vitamin D dose, and duration of follow-up. Vitamin D supplementation ranged from 400 IU/day for an average of 7.1 years, to a single 300, 000 IU dose. The main tools used to capture quality of life were adaptations of validated, questionnaires (Medical Outcomes Study Short Form 36-item questionnaire and EuroQOL five dimension questionnaire). Vitamin D supplementation was not associated with significant changes in quality of life. Studies that reported changes in quality of life as a result of vitamin D supplementation were in clinical populations on short-term vitamin D. Most articles reviewed displayed poor methodologic quality (eg, no randomization/blinding, dropout description, or vitamin D assessment). Current evidence indicates that vitamin D supplementation may have a small to moderate effect on quality of life when used on a short-term basis in diseased populations. However, the evidence for a beneficial effect of long-term vitamin D supplementation on health-related quality of life is lacking.