Interactive associations of dietary vitamins and α-linolenic acid with type 2 diabetes: a cross-sectional analysis of NHANES 2003—2018

Abstract Limited evidence exists on whether vitamins enhance the effect of α-linolenic acid (ALA) on type 2 diabetes (T2D). Therefore, this study aims to evaluate the interactive relationship between dietary vitamins and ALA in relation to T2D among U.S. adults. This cross-sectional study included 16,290 adults aged ≥ 18 years from the National Health and Nutrition Examination Survey (NHANES) 2003-2018. Dietary intake was assessed using two-day, 24 h dietary recalls. Daily intakes of ALA and nine vitamins were estimated. T2D was defined using fasting glucose, glycohemoglobin levels, or self-reported medication or insulin use. Binary logistic regression and restricted cubic spline analyses were performed to evaluate the interactive associations between dietary ALA, vitamins, and T2D. ALA and vitamin intakes were associated with an 18%-35% and 21%-59% lower risk of T2D, respectively. After adjusting for confounders, dietary ALA exhibited a non-linear, “U-shaped” association with T2D ( p = 0.0006). This association was stronger in the highest tertile of several vitamins (A, D, E, B6, B12, and C), particularly vitamin B12. Among females, higher vitamin B12 intake enhanced the protective effect of ALA against T2D, with odds ratios (95% confidence interval) ranging from 0.6 (0.4-0.7) to 0.5 (0.3-0.8). Although higher tertiles of certain vitamins may significantly enhance the protective effect of ALA against T2D, the effect was weaker than that of vitamin B12. In conclusions, higher vitamin B12 intake may enhance the association between ALA and reduced T2D risk, particularly among females.