Higher dietary intake of alpha-linolenic acid is associated with lower insulin resistance in middle-aged Japanese

Objective: To investigate the associations between dietary intake of n-3 polyunsaturated fatty acids (plant-derived alpha-linolenic acid: ALA, and marine-derived eicosapentaenoic and docosahexaenoic acid: EPA. +. DHA) and insulin resistance (IR) in a lean population with high n-3 PUFA intake. Method: We cross-sectionally studied 3383 Japanese local government workers aged 35-66 in 2002. IR was defined as the highest quartile of homeostasis model assessment, and nutrient intake was estimated from a diet history questionnaire. The odds ratios (ORs) of IR taking the lowest quartile of ALA or EPA. +. DHA intake as the reference were calculated by logistic regression analysis. Results: Mean age, body mass index (BMI), and dietary ALA, and median of dietary EPA+DHA were 47.9years, 22.9kg/m², and 1.90g/day (0.88%E) and 0.77g/day (0.36%E), respectively. The ORs of IR decreased across the quartiles of ALA intake (multivariate-adjusted OR for Q4 versus Q1=0.74, P for trend=0.01) and the association was observed only in subjects with a BMI of <25kg/m² (P for interaction=0.033). However EPA+DHA showed no such associations consistently. Conclusion: Higher ALA intake was significantly associated with a lower prevalence of IR in normal weight individuals of middle-aged Japanese men and women.