Moderate alcohol intake is associated with decreased risk of insulin resistance among individuals with vitamin D insufficiency

Objective To determine whether moderate alcohol intake modifies the association between low vitamin D levels and insulin resistance (IR), we hypothesized that moderate alcohol intake would have a modifying effect on IR in people with low vitamin D levels. Methods This was a cross-sectional analysis of subjects ≥20 y old without a history of diabetes, coronary heart disease, or stroke in the National Health and Nutrition Examination Survey 2001–2004. Main outcome was IR status measured by homeostasis model assessment for IR (HOMA-IR; ≥ 2.6) and fasting insulin (>12.2 μU/mL) in moderate drinkers compared with non-drinkers by vitamin D levels (deficient ≤20 ng/mL, insufficient 21–32 ng/mL, normal >32 ng/mL). Results Two thousand seven hundred twenty-one subjects met the inclusion criteria, representing a weighted total of >138 million people. Of these, 34% were vitamin D deficient and 47% insufficient. In adjusted analysis, compared with moderate drinkers with normal vitamin D levels, non-drinkers had no increased risk of IR by HOMA-IR levels (odds ratio [OR] 1.18, 95% confidence interval [CI] 0.61–2.30). Vitamin D–deficient individuals had a higher risk of IR regardless of alcohol consumption (moderate drinkers OR 2.12, 95% CI 1.41–3.19; non-drinkers OR 2.22, 95% CI 1.29–3.83). However, in those with insufficient vitamin D levels, moderate alcohol intake had a modifying effect on the odds of IR, with no difference seen in moderate drinkers (OR 1.29, 95% CI 0.92–1.80) and an increased risk found in non-drinkers (OR 1.82, 95% CI 1.07–3.11). Similar results were seen with fasting insulin. Conclusion Moderate alcohol consumption appears to have a modifying effect on the risk of IR in individuals with insufficient levels of vitamin D.