Though vitamin D is crucial for bone health, there continues much debate about other health outcomes. Observational studies have suggested an association between a low 25-hydroxyvitamin D level and the risk of type 2 diabetes.
Vitamin D - no defense against T2D
New research published in the New England Journal of Medicine on June 7, 2019, and presented last week during the annual American Diabetes Association scientific sessions discounts a role for vitamin D in prevention of type 2 diabetes. Two of the study authors are researchers from Duke, both in the division of general internal medicine: Dr. Ranee Chatterjee and Dr. Rowena Dolor.
A large randomized controlled trial
This was a big study — 22 cities across the U.S., enrollment of 2,423 adults at high risk for type 2 diabetes, designed as a randomized, double-blind, placebo-controlled clinical trial assigning participants randomly to either take 4,000 International Units (IU) of the D3 (cholecalciferol) form of vitamin D or a placebo pill daily.
The bottom line
Vitamin D supplements are not a defense against diabetes.
The results paper in NEJM appears as an original research article titled: "Vitamin D Supplementation and Prevention of Type 2 Diabetes". After a median follow-up of 2.5 years, the primary outcome of diabetes occurred in 293 participants in the vitamin D group and 323 in the placebo group. The hazard ratio for vitamin D as compared with placebo was 0.88.
Recently, from the same study population, Chatterjee, as first author along with Dolor as a co-author, reported in Contemporary Clinical Trials about risk of vitamin D and cancer. The paper is "Vitamin D supplementation for prevention of cancer: The D2d cancer outcomes (D2dCA) study". Results will help guide future research and clinical recommendations related to vitamin D and cancer risk.
Citation: Pittas AG, Dawson-hughes B, Sheehan P, et al. Vitamin D Supplementation and Prevention of Type 2 Diabetes. N Engl J Med. 2019; DOI: 10.1056/NEJMoa1900906