Effects of Vitamin D3 and Yeast Beta-Glucan Supplementation on Glycemic Control and Cardiovascular Disease Risk in Patients With Type 2 Diabetes

The goal of this randomized, double-blind, placebo-controlled trial, with a 2×2 factorial design in individuals with type 2 diabetes (T2D), is to investigate (a) the effect of daily dietary supplementation with vitamin D3 (1600 IU) or yeast β-glucan (600 mg) on glycemic control in patients with T2D and (b) whether vitamin D3 (1600 IU) or yeast β-glucan (600 mg) supplementation reduces the predicted 10 year risk of atherosclerotic cardiovascular disease (ASCVD) in patients with T2D. Approximately 2,500 subjects aged 40-79 with T2D will be included in this study. Eligible participants will be randomly assigned to one of four groups: (1) daily vitamin D3 (1600 IU) and yeast β-glucan (600 mg); (2) daily vitamin D3 (1600 IU) and placebo for yeast β-glucan; (3) daily placebo for vitamin D3 and yeast β-glucan (600 mg); or (4) daily placebo for vitamin D3 and placebo for yeast β-glucan. At baseline, questionnaires will be administered to collect data on sociodemographic factors, lifestyle habits, health status, cognitive function, and medical conditions, et al. Participants will also undergo physical measurements, and blood, urine, and feces samples will be collected at study centers. The study includes a 2-year intervention period followed by a 3-year post-intervention follow-up. Participants in all groups will take four capsules daily for 2 years: two capsules containing either vitamin D or its placebo and two capsules containing either yeast β-glucan or its placebo. During the 2-year intervention period, questionnaires, physical measurements, and sample collection will be conducted at 6, 12, and 24 months. This trial will also evaluate the effects of supplementation on cardiometabolic risk factors, inflammatory markers, and liver and kidney function indicators, and assess whether it reduces the risk of cardiovascular disease, microvascular complications, and mortality over the 3-year post-intervention period, providing scientific evidence for the health effects of vitamin D or yeast β-glucan in the T2D population.