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

Inclusion Criteria: 1. Type 2 diabetes mellitus diagnosed by a physician based on the diagnostic criteria outlined in the Guideline for the Prevention and Treatment of Diabetes Mellitus in China (2024 Edition); 2. Men or women aged 40-79 years; 3. Convenient access to the study centers and permanent residence in the vicinity for the next five years; 4. Voluntary participation and signed written informed consent. Exclusion Criteria: 1. History of clinical cardiovascular disease (including myocardial infarction, treatment or hospitalization for heart failure, stroke, and coronary revascularization) within the past 6 months; 2. History of severe diabetic microvascular complications (diabetic nephropathy with an estimated glomerular filtration rate (eGFR) \< 30 mL/(min·1.73m²), proliferative diabetic retinopathy, confirmed diabetic peripheral neuropathy with abnormal nerve conduction studies or small fiber neuropathy testing); 3. History of cancer, excluding non-melanoma skin cancer or cancers with a favorable prognosis; 4. History of kidney stones, hypercalcemia, or hyperparathyroidism; 5. History of severe liver disease, severe kidney disease, severe gastrointestinal disease, severe infectious diseases, severe sarcoidosis or other granulomatous diseases, severe mental illness, or any other condition considered unsuitable for participation judged by the clinic team; 6. Laboratory evaluation: * Blood calcium levels greater than or equal to the normal range for the clinical site's laboratory; * Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) levels higher than 3 times the normal range for the clinical site's laboratory; * eGFR \< 30 mL/(min·1.73m²); 7. Individuals currently taking vitamin D supplements (\>400 IU/day), calcium supplements (\>600 mg/day), yeast β-glucan supplements (\>250 mg/day), or those with a history of allergy or intolerance to vitamin D or prebiotic products; 8. Participation in other clinical trials within the past 3 months; 9. Planning to become pregnant within the next five years, or currently pregnant or breastfeeding.