Low levels of vitamin D have been linked with a higher risk of developing type 2 diabetes; however, limited research is available on whether vitamin D supplements can reduce the possibility of acquiring the disease. New study findings from the University of Eastern Finland assessed the use of higher doses of vitamin D in relation to the incidence of type 2 diabetes in healthy older adults, finding minimal effect.1
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Many individuals experience vitamin D deficiency as their diet does not meet The Institutes of Medicine’s recommended dose of 600 international units (IU) of vitamin D per day.2 On average, an individual receives around 168 to 204 IU of vitamin D daily from food intake, according to the 2015–2016 National Health and Nutrition Examination Survey.3
“Effects of vitamin D supplementation on glucose metabolism are plausible, because the physiologically active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)2D), is directly involved in the regulation of glucose metabolism by improving islet functioning and reducing insulin resistance,” wrote the authors of the study, in a news release.4
Previously conducted experimental studies have displayed that the intake of significantly higher doses of vitamin D slightly reduces the risk of developing type 2 diabetes in individuals with impaired glucose metabolism (prediabetes). However, the study authors noted that no effects have been demonstrated among individuals without prediabetes.1
The researchers conducted a double-blind, placebo-controlled Finnish Vitamin D, randomized controlled trial which extended from 2012 to 2018. The study assessed the use of vitamin D supplemental compared to a placebo in relation to the risk of type 2 diabetes, including a total of 2495 generally healthy older individuals. Men participants were aged 60 years and older and women aged 65 years and older.1,4
The individuals were categorized into 3 groups and were randomly assigned to receive either a placebo, 40 micrograms of vitamin D3 per day, or 80 micrograms of vitamin D3 per day. The study authors noted that the prespecified primary and secondary outcomes were occurrence of cardiovascular disease and cancer, along with the incidence of type 2 diabetes as a prespecified tertiary outcome.1,4
The researchers also included a subcohort group of 505 individuals, closely monitoring available blood samples to evaluate blood calcidoil levels, which describes the body’s vitamin D status to further identify the incidence of type 2 diabetes.1,4
Throughout the 5-year study period, the results demonstrated that 105 individuals developed type 2 diabetes, with 38 in the placebo group, 31 in the group receiving 40 micrograms of vitamin D3 per day, and 36 in the group receiving 80 micrograms of vitamin D3 per day. The results did not display a significant difference in the number of cases between the 3 groups.1,4
In the subcohort analyses, the average blood calcidiol level was 75 nanomoles per liter (nmol/L) at the start, apart from levels below 50 nmol/l among 9% of individuals. In a 12-month follow-up the average calcoidiol level was 100 nmol/l in the 40-microgram vitamin D group and 120 nmol/l in the 80-microgram vitamin D group, with no significant change among the placebo group.1
The subcohort analyses also assessed the effects of vitamin D on blood glucose, insulin levels, body mass index, and waist circumference during the first 2 years of the study, but no differences were observed between the 3 groups, according to study authors.1
The findings suggest that higher doses of vitamin D than recommended does not significantly impact the risk of developing type 2 diabetes among individuals without prediabetes who already have tolerable vitamin D status. However, the study authors noted that the results do not exclude the influence of high-dose vitamin D supplementation among vitamin D–deficient populations with an average risk for type 2 diabetes.1,4
REFERENCES
1. Taking high-dose vitamin D supplements for five years did not affect the incidence of type 2 diabetes. EurekAlert. News release. December 3, 2024. Accessed December 9, 2024. https://www.eurekalert.org/news-releases/1066890.
2. Vitamin D supplements may lower blood pressure in older people with obesity. News release. EurekAlert!. November 12, 2024. Accessed December 9, 2024. https://www.eurekalert.org/news-releases/1063997.
3. Vitamin D. National Institutes of Health. July 26, 2024. Accessed December 9, 2024. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.
4. The effect of vitamin D3 supplementation on the incidence of type 2 diabetes in healthy older adults not at high risk for diabetes (FIND): a randomized controlled trial. Springer Nature Link. News release. December 2, 2024. Accessed December 9, 2024. https://link.springer.com/article/10.1007/s00125-024-06336-9.