title: Effect of alpha-tocopherol and beta-carotene supplementation on the incidence of type 2 diabetes.
abstract: OBJECTIVE
  Type 2 diabetes is associated with reduced antioxidant defence. Only a few human studies have investigated the role of antioxidants in the pathogenesis of diabetes. This study aimed to examine whether alpha-tocopherol or beta-carotene affected the occurrence of type 2 diabetes.
  
  
  METHODS
  In the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study, a double-blind, controlled trial, 29,133 male smokers aged 50-69 years were randomised to receive either alpha-tocopherol (50 mg/day) or beta-carotene (20 mg/day) or both agents or placebo daily for 5-8 years (median 6.1 years). Baseline serum samples were analysed for alpha-tocopherol and beta-carotene using HPLC. Cases of diabetes were identified from a nationwide Finnish registry of patients receiving drug reimbursement for diabetes. Of 27,379 men without diabetes at baseline, 705 men were diagnosed with diabetes during the follow-up of up to 12.5 years.
  
  
  RESULTS
  Baseline serum levels of alpha-tocopherol and beta-carotene were not associated with the risk of diabetes in the placebo group: the relative risk (RR) between the highest and lowest quintiles of alpha-tocopherol was 1.59 (95% CI 0.89-2.84) and that for beta-carotene was 0.66 (95% CI 0.40-1.10). Neither supplementation significantly affected the incidence of diabetes: the RR was 0.92 (95% CI 0.79-1.07) for participants receiving alpha-tocopherol compared with non-recipients and 0.99 (95% CI 0.85-1.15) for participants receiving beta-carotene compared with non-recipients.
  
  
  CONCLUSIONS
  Neither alpha-tocopherol nor beta-carotene supplementation prevented type 2 diabetes in male smokers. Serum levels of alpha-tocopherol and beta-carotene were not associated with the risk of type 2 diabetes.
authors.affiliation: Department of Health Promotion and Chronic Disease Prevention, National Public Health Institute, Mannerheimintie 166, 00300, Helsinki, Finland. merja.kataja-tuomola@ktl.fi
authors.forename: M
authors.initials: M
authors.lastname: Kataja-Tuomola
authors.forename: J R
authors.initials: JR
authors.lastname: Sundell
authors.forename: S
authors.initials: S
authors.lastname: Männistö
authors.forename: M J
authors.initials: MJ
authors.lastname: Virtanen
authors.forename: J
authors.initials: J
authors.lastname: Kontto
authors.forename: D
authors.initials: D
authors.lastname: Albanes
authors.forename: J
authors.initials: J
authors.lastname: Virtamo
mesh_terms: D000368:Aged; D000975:Antioxidants / Q000627:therapeutic use; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology* / Q000517:prevention & control*; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010919:Placebos; D012306:Risk; D012907:Smoking; D013997:Time Factors; D024502:alpha-Tocopherol / Q000097:blood / Q000627:therapeutic use*; D019207:beta Carotene / Q000097:blood / Q000627:therapeutic use*
chemical_list: D000975:Antioxidants; D010919:Placebos; D019207:beta Carotene; D024502:alpha-Tocopherol