Effects of Vitamin D3 and Yeast Beta-Glucan Supplementation on Cardiovascular Disease in Patients with Type 2 Diabetes

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.

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 the effects of vitamin D or yeast β-glucan supplementation on major cardiovascular diseases. Approximately 8,000 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 (600 mg); (3) daily placebo for vitamin D3 (1600 IU) and yeast β-glucan (600 mg); or (4) daily placebo for vitamin D3 (1600 IU) and placebo for yeast β-glucan (600 mg).

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 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. On-site follow-ups, including questionnaires, physical measurements, and sample collection, will be conducted at 6, 12, 24 and 60 months.

This study will also evaluate the effects on all-cause mortality, microvascular complications, cognitive function, and other outcomes, providing scientific evidence for the health effects of vitamin D or yeast β-glucan in individuals with type 2 diabetes.

Eligibility Criteria:
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.