Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

BACKGROUND: The evidence for vitamin D and other agents that experimentally modulate T regulatory cells (Tregs) for the treatment of patients with autoimmune or allergic diseases has not been established. OBJECTIVE: We have undertaken a systematic review of randomised controlled trials to assess the efficacy of vitamin D, vitamin A, niacin and short-chain fatty acids in enhancing absolute Treg numbers and phenotypes in patients with inflammatory or autoimmune disease. METHODS: This systematic review was conducted using a predefined protocol (PROSPERO International prospective register of systematic reviews, ID = CRD42016048648/ CRD42016048646). Randomised controlled trials of patients with inflammatory or autoimmune disease or healthy participants which compared either oral vitamin D or vitamin A or short-chain fatty acids with control or placebo and measured the absolute concentration of proportion of Tregs were eligible for inclusion. Searches of electronic databases (CENTRAL, MEDLINE, EMBASE, CINAHL, PUBMED and Web of Science) identified eight eligible independent trials (seven autoimmune disease trials, one trial of healthy subjects). Data were extracted by two reviewers and the risk of study bias was assessed using Cochrane Collaboration methodology. RESULTS: Planned meta-analysis was not possible due to the heterogeneous nature of the studies. Nevertheless, in five trials of autoimmune disorders which measured the proportion of Tregs, a higher proportion was observed in the vitamin D group compared to controls at 12 months in all but one trial. In the trial of healthy subjects, a significant difference was reported, with a higher percentage of Tregs observed in the vitamin D group (at 12 weeks, mean 6.4% (SD 0.8%) (vitamin D) vs 5.5% (1.0%) (placebo). There were no trials to assess the efficacy of vitamin A, niacin and short-chain fatty acids in enhancing absolute Treg numbers. CONCLUSIONS: Vitamin D supplementation may increase Treg/CD3 ratios in both healthy individuals and patients with autoimmune disorders and may increase Treg function. There remains a need for further suitably powered clinical studies aimed at enhancing Treg numbers and/or function.

Original publication




Journal article


PLoS One

Publication Date





Autoimmune Diseases, Humans, Inflammation, Lymphocyte Count, T-Lymphocytes, Regulatory, Vitamin D