Effects of vitamin D supplementation on the regulation of blood lipid levels in prediabetic subjects: A meta-analysis

This meta-analysis aimed to systematically investigate whether vitamin D supplementation reduces blood lipid-total cholesterol (TC), LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), and triglyceride (TG)-levels in prediabetic individuals. Pubmed, Web of Science, Cochrane Library, Embase, CNKI, and WANFANG databases were searched for studies published before 13 February 2022 (including 13 February 2022). Five articles were included. The results showed that vitamin D intervention led to a significant reduction in TG compared with control or placebo treatment (-0.42 [-0.59, -0.25], P < 0.001). Subgroup analyses showed that this effect was particularly significant among the studies that included obese subjects (-0.46 [-0.65, -0.28], P < 0.001), the studies that also included men (not only women) (-0.56 [-0.78, -0.34], P < 0.001), and the studies with intervention durations longer than 1 year (-0.46 [-0.65, -0.28], P < 0.001). Both relatively low doses of 2,857 IU/day (-0.65 [-0.92, -0.38], P < 0.001) and relatively high doses of 8,571 IU/day (-0.28 [-0.54, -0.02] P = 0.04) of vitamin D supplementation reduced TG levels, and the effect was observed both in Northern Europe (-0.65 [-0.92, -0.38], P < 0.001) and Asian (-0.25 [-0.48, -0.03], P = 0.03) country subgroups. No significant effects on TC, HDL-C, and LDL-C were shown. In conclusion, vitamin D supplementation might beneficially affect TG levels in individuals with prediabetes. Particularly longer durations of treatment, more than 1 year, with doses that correct vitamin deficiency/insufficiency, can have a beneficial effect. This meta-analysis was registered at www.crd.york.ac.uk/prospero (CRD42020160780).