Some patients with prediabetes may benefit from vitamin D
Dr. Pittas advised that although the overall effect is modest in people with prediabetes who aren’t selected for vitamin D deficiency, “given how prevalent prediabetes and type 2 diabetes are, clinicians and patients should consider vitamin D supplementation as an adjunct to weight loss for diabetes prevention. Based on analyses from the D2d study, people with prediabetes who have low levels of vitamin D and are nonobese derive the most benefit.”
He noted that secondary analyses from D2d also suggest greater benefit among those achieving higher blood levels of vitamin D, but that high supplemental doses could cause adverse musculoskeletal outcomes in older adults, “so the benefit–harm ratio needs to be ascertained individually.”
Dr. Christides advised, “Until further data are available from high-quality randomized trials, health care professionals should continue to discuss with patients the musculoskeletal health benefits of vitamin D and support them to achieve and maintain lifestyle changes that, although challenging to sustain, are known to decrease development of [type 2 diabetes].”
DPVD: Hint of benefit in those with greater insulin resistance
The double-blind, multicenter, randomized, placebo-controlled DPVD trial took place from June 1, 2013, through Aug. 31, 2015, and involved 1,256 participants with impaired glucose tolerance (with or without impaired fasting glucose) from 32 institutions in Japan. They were randomized 1:1 to receive eldecalcitol or placebo for 3 years.
During the 3-year period, 12.5% of the 630 patients in the eldecalcitol group and 14.2% of the 626 patients in the placebo group developed diabetes. The difference was not significant, with a hazard ratio (HR) of 0.87 (P = .39). There was no difference in regression to normoglycemia, which had occurred in 23.0% with eldecalcitol versus 20.1% with placebo by the end of the study (P = .21).
However, eldecalcitol was effective for preventing the development of type 2 diabetes after adjustment for prespecified variables, including age, sex, hypertension, body mass index, family history of diabetes, 2-hour plasma glucose, 25-hydroxyvitamin D, and insulin resistance (HR, 0.69; P = .02).
In a post hoc analysis, eldecalcitol significantly prevented the development of type 2 diabetes among those with the lowest divisions of homeostatic model assessment (HOMA)-β (HR, 0.35; P < .001), HOMA-insulin resistance (HR, 0.37; P = .001), and fasting immunoreactive insulin (HR, 0.41; P = .001).
“These results indicate that eldecalcitol had a beneficial effect on insufficient basal insulin secretion,” Dr. Kawahara and colleagues wrote.
Discontinuations due to adverse events occurred in 4.1% with eldecalcitol and 3.4% in the placebo group (HR, 1.23; P = .47). Rates and types of adverse events didn’t differ significantly between the two groups.
The study was supported by a grant from the Kitakyushu Medical Association. The authors had no further disclosures. Dr. Christides had no disclosures. Dr. Pittas has reported receiving funding from the National Institutes of Health.
A version of this article first appeared on Medscape.com.