Serum and dietary β-carotene and α-tocopherol and incidence of type 2 diabetes mellitus in a community-based study of Swedish men: report from the Uppsala Longitudinal Study of Adult Men (ULSAM) study

Aims/hypothesis To investigate the association of serum concentrations and dietary intake of beta-carotene and alpha-tocopherol with type 2 diabetes incidence. Methods Serum beta-carotene, a-tocopherol, lifestyle factors (BMI, physical activity and smoking) and metabolic factors (insulin sensitivity [homeostasis model assessment], acute insulin response and impaired fasting glucose) were analysed in 846 50-year-old non-diabetic Swedish men (participants in the Uppsala Longitudinal Study of Adult Men). Diabetes was identified in 245 participants at reinvestigations after 10, 20 and 27 years. At the 20 year reinvestigation, dietary intake of beta-carotene and alpha-tocopherol, insulin sensitivity (euglycaemic-hyperinsulinaemic clamp) and insulin secretion (early insulin response in OGTT) were determined. Results The highest tertile of serum beta-carotene at age 50 (>0.335 mu mol/l) was associated with 59% lower risk of diabetes during follow-up compared with the lowest tertile (<0.210 mu mol/l) after adjustment for lifestyle and metabolic factors (p<0.01). The highest tertile of lipid-corrected serum alpha-tocopherol at age 50 (>3.67 mu mol/mmol) was associated with 46% lower risk of diabetes compared with the lowest tertile (<3.25 mu mol/mmol) independently of metabolic factors (p<0.05). Moreover, lower serum beta-carotene and alpha-tocopherol concentrations were independently associated with impaired insulin sensitivity (p<0.001), but not with early insulin response, in a subsample of non-diabetic individuals 20 years later. Dietary intake of beta-carotene and alpha-tocopherol independently predicted type 2 diabetes during 7 years of follow-up. Conclusions/interpretation Serum concentrations and dietary intakes of beta-carotene and alpha-tocopherol independently predicted insulin resistance and type 2 diabetes incidence during 27 years of follow-up in a community-based study of men. This result supports the importance of impaired antioxidant status for the development of insulin resistance and type 2 diabetes.