This study is a randomized, double-blind, placebo-controlled trial involving 8,000 individuals aged 40-79 with type 2 diabetes. The trial includes a 2-year intervention period followed by 3 years of follow-up. The primary objective is to investigate whether daily dietary supplementation with vitamin D3 (1600 IU) or yeast β-glucan (600 mg) reduces the risk of major cardiovascular diseases, including myocardial infarction, stroke, treated or hospitalized heart failure, and cardiovascular deaths. The secondary objectives include evaluating the effects of vitamin D3 or yeast β-glucan supplementation on all-cause mortality, microvascular disease, cognitive function, and other outcomes.