While a number of studies revere vitamin D as a molecule with the potential to heal various diseases due to associations between low vitamin D levels and certain disease states, a large genetic study from the University of Cambridge doubts vitamin D plays a role in developing type 2 diabetes. “Association Between Circulating 25-Hydroxyvitamin D and Type 2 Diabetes: A Mendelian Randomization Study,” published in the journal Lancet, suggests increasing circulating vitamin D might not reduce type 2 diabetes risk, necessitating further studies to identify ways to prevent type 2 diabetes.
“Our findings suggest that interventions to reduce the risk of type 2 diabetes by increasing concentrations of vitamin D are not currently justified,” said Dr. Nita Forouhi, principal investigator on the study, in a news release. “Observational studies that show a strong and consistent higher risk of type 2 diabetes with lower levels of vitamin D may do so because they have thus far not been able to adequately control for distorting or confounding factors, such as physical activity levels, that may be related both to vitamin D levels and to the risk of type 2 diabetes.” Essentially, correlation does not mean causation.
To investigate the relationship, Dr. Forouhi and colleagues used mendelian randomization to study single nucleotide polymorphisms, a type of genetic alteration. The alterations of interest were in the genes DHCR7, CYP2R1, DBP, and CYP24A1, all of which are related to vitamin D synthesis, metabolism, or transport. A total of 28,144 diabetic patients and 76,344 non-diabetic participants were analyzed for circulating vitamin D levels and glycaemic parameters.
While all genetic alterations were associated with low vitamin D levels, glycaemic traits were not significantly related, and the type 2 diabetes odds ratio was 0.93 per 25.0 nmol/L lower vitamin D concentration. According to Dr. Forouhi, these results are consistent with randomized, controlled trials that failed to find a protective effect of vitamin D for type 2 diabetes prevention.
“While our current findings do not provide support for a causal role of vitamin D in the development of type 2 diabetes, we are far from done with this topic,” stated Dr. Forouhi. “Further research is yet needed with both better clinical trials and better observational studies with more precise measurement of important factors that may affect vitamin D and disease relationships. Until then, we need to be cautious about vitamin D’s potential role in the prevention of type 2 diabetes and stick to things that are proven to work — diet and exercise.”