A low serum 25-hydroxyvitamin D [(25(OH) D)] concentration was shown to correlate with higher fasting blood glucose (FBG) and insulin levels. Since age affect insulin sensitivity and the metabolism, we aimed in this randomized controlled trial to investigate the effect of vitamin D supplementation on glucose homeostasis and index of insulin resistance in elderly subjects living in Beirut, Lebanon.

Participants (n= 115) deficient in vitamin D were randomly divided into two groups, a group receiving 30,000 IU cholecalciferol/week for a period of 6 months, and a placebo group. The index of insulin resistance HOMA (homeostasis model assessment) was the primary outcome. Glucose homeostasis and metabolic markers were also measured at start of treatment and at 6 months.

Vitamin D supplementation led to significant improvements in blood levels of [25(OH) D] (P< 0.0001), and a significant decreased of HOMA, PTH and FBG concentrations (P< 0.0001) in the intervention group compared to placebo. No significant changes were observed in HbA1c levels for both groups. Total cholesterol and LDL cholesterol concentrations have also decreased significantly in the intervention group (P< 0.0001).

Short-term supplementation with cholecalciferol improved vitamin D status, and markers of insulin resistance in healthy elder population. This trial was registered at ClinicalTrials.gov; Identifier number#:NCT03478475