Higher serum β-carotene levels, associated with higher intake of green and yellow vegetables, confer beneficial effects against insulin resistance. - GreenMedInfo Summary

OBJECTIVE: Although green and yellow vegetables have beneficial effects against type 2 diabetes, the relationship of their nutritive content with insulin resistance is poorly understood. The aim of this study was to examine the associations of serumβ-carotene and retinol concentrations with glucose and insulin concentrations.

METHODS: We recruited 951 Japanese men and women ages 30 to 79 y who were not undergoing treatment for diabetes and measured their serum β-carotene and retinol concentrations. A 75-g oral glucose tolerance test was performed and the homeostasis model assessment for insulin resistance (HOMA-IR) and the Matsuda Index were calculated as measures of insulin resistance. Several confounding factors were adjusted for with multivariable logistic models.

RESULTS: Multivariable-adjusted odds ratios of the highest quartile of serumβ-carotene compared with the lowest quartile for HOMA-IR>1.6 and Matsuda Index<4.9 were 0.56 (95% confidence interval, 0.34-0.94) and 0.62 (0.37-1.02), respectively. When stratified by sex and overweight status, these associations were observed for women and non-overweight individuals. Serum retinol concentration was not associated with either index. Furthermore, according to the nutritional survey, serumβ-carotene concentration was associated with green and yellow vegetable intake (P = 0.01).

CONCLUSION: Our findings suggest that higher serumβ-carotene levels, associated with higher intake of green and yellow vegetables, confer beneficial effects against insulin resistance.