Effects of vitamins C and E and beta-carotene on the risk of type 2 diabetes in women at high risk of cardiovascular disease: a randomized controlled trial.
BACKGROUND
Vitamin C, vitamin E, and beta-carotene are major antioxidants and as such may protect against the development of type 2 diabetes via reduction of oxidative stress.


OBJECTIVE
The purpose of this study was to investigate the long-term effects of supplementation with vitamin C, vitamin E, and beta-carotene for primary prevention of type 2 diabetes.


METHODS
In the Women's Antioxidant Cardiovascular Study, a randomized trial that occurred between 1995 and 2005, 8171 female health professionals aged > or =40 y with either a history of cardiovascular disease (CVD) or > or =3 CVD risk factors were randomly assigned to receive vitamin C (ascorbic acid, 500 mg every day), vitamin E (RRR-alpha-tocopherol acetate, 600 IU every other day), beta-carotene (50 mg every other day), or their respective placebos.


RESULTS
During a median follow-up of 9.2 y, a total of 895 incident cases occurred among 6574 women who were free of diabetes at baseline. There was a trend toward a modest reduction in diabetes risk in women assigned to receive vitamin C compared with those assigned to receive placebo [relative risk (RR): 0.89; 95% CI: 0.78, 1.02; P = 0.09], whereas a trend for a slight elevation in diabetes risk was observed for vitamin E treatment (RR: 1.13; 95% CI: 0.99, 1.29; P = 0.07). However, neither of these effects reached statistical significance. No significant effect was observed for beta-carotene treatment (RR: 0.97; 95% CI: 0.85, 1.11; P = 0.68).


CONCLUSIONS
Our randomized trial data showed no significant overall effects of vitamin C, vitamin E, and beta-carotene on risk of developing type 2 diabetes in women at high risk of CVD. This trial was registered at clinicaltrials.gov as NCT00000541.
Song
Yiqing
Y
Division of Preventive Medicine and Cardiology Division, Harvard School of Public Health, Boston, MA 02215, USA. ysong3@rics.bwh.harvard.edu
Cook
Nancy R
NR
Albert
Christine M
CM
Van Denburgh
Martin
M
Manson
JoAnn E
JE
D000368:Aged; D000975:Antioxidants / Q000008:administration & dosage* / Q000494:pharmacology; D001205:Ascorbic Acid / Q000008:administration & dosage* / Q000494:pharmacology; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000517:prevention & control*; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000517:prevention & control*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D016017:Odds Ratio; D018384:Oxidative Stress / Q000187:drug effects; D011322:Primary Prevention; D018570:Risk Assessment; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D014810:Vitamin E / Q000008:administration & dosage* / Q000494:pharmacology; D019207:beta Carotene / Q000008:administration & dosage* / Q000494:pharmacology
D000975:Antioxidants; D019207:beta Carotene; D014810:Vitamin E; D001205:Ascorbic Acid