Prediabetes and insulin resistance: effect of vitamin D

Purpose of review The impact of vitamin D on improving insulin resistance in prediabetes remains controversial. The purpose of this review is to examine whether vitamin D supplementation improves insulin resistance in adults with prediabetes, and if so, to identify the mechanisms and the specific populations. Recent findings Global prevalence of prediabetes is increasing, and prevention is a critical issue because these people with prediabetes will develop type 2 diabetes soon, which will put pressure on healthcare costs. Recent evidence on the effectiveness of vitamin D administration in improving insulin resistance and preventing the onset of type 2 diabetes in adults with prediabetes has been accumulating. The 2024 updated clinical practice guideline of the American Diabetes Association states that vitamin D administration to patients with prediabetes potentially benefits type 2 diabetes incidence in specific populations. There are also reports that vitamin D administration improves insulin resistance via increased serum osteocalcin levels, a marker of bone turnover. Summary Vitamin D is likely to improve insulin resistance, which is already present at the time of prediabetes. However, the effectiveness may vary depending on ethnic differences and blood vitamin D levels at the start of administration.