Long-term beta-carotene supplementation and risk of type 2 diabetes mellitus: a randomized controlled trial.
BACKGROUND
Recent data suggest a protective role of carotenoids in the development of type 2 diabetes mellitus (DM), possibly via an antioxidant effect, but no randomized trial has directly assessed the efficacy of beta-carotene to prevent DM.


OBJECTIVE
To determine whether long-term beta-carotene supplementation reduces the risk of developing type 2 DM.


METHODS
A total of 22, 071 healthy US male physicians aged 40 to 84 years in a randomized, double- blind, placebo-controlled trial, from 1982 to 1995. More than 99% of the participants had complete follow-up (median duration, 12 years).


METHODS
Subjects were randomly assigned to receive beta-carotene (50 mg on alternate days) or placebo.


METHODS
Incidence of type 2 DM.


RESULTS
A total of 10, 756 subjects were assigned to beta-carotene and 10, 712 to placebo. Incidence of type 2 DM did not differ between groups: 396 men in the beta-carotene group and 402 men in the placebo group developed type 2 DM (relative risk, 0.98; 95% confidence interval, 0.85-1.12). The lack of association between beta-carotene supplementation and incidence of type 2 DM persisted despite multivariate adjustment. There was no evidence of benefit when the period of risk was subdivided into years of follow-up or increasing duration of treatment.


CONCLUSIONS
In this trial of apparently healthy men, supplementation with beta-carotene for an average of 12 years had no effect on the risk of subsequent type 2 DM.
Liu
S
S
Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02215, USA. simin.liu@channing.harvard.edu
Ajani
U
U
Chae
C
C
Hennekens
C
C
Buring
J E
JE
Manson
J E
JE
D000328:Adult; 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; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012306:Risk; D019207:beta Carotene / Q000627:therapeutic use*
D000975:Antioxidants; D019207:beta Carotene