Article

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.

Division of Preventive Medicine and Cardiology Division, Harvard School of Public Health, Boston, MA 02215, USA.
American Journal of Clinical Nutrition (Impact Factor: 6.5). 06/2009; 90(2):429-37. DOI: 10.3945/ajcn.2009.27491
Source: PubMed

ABSTRACT 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.
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.
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.
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).
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.

1 Bookmark
 · 
47 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Increasing evidence indicates that reactive oxygen species (ROS), consisting of superoxide, hydrogen peroxide, and multiple others, do not only cause oxidative stress, but rather may function as signaling molecules that promote health by preventing or delaying a number of chronic diseases, and ultimately extend lifespan. While high levels of ROS are generally accepted to cause cellular damage and to promote aging, low levels of these may rather improve systemic defense mechanisms by inducing an adaptive response. This concept has been named mitochondrial hormesis or mitohormesis. We here evaluate and summarize more than 500 publications from current literature regarding such ROS-mediated low-dose signaling events, including calorie restriction, hypoxia, temperature stress, and physical activity, as well as signaling events downstream of insulin/IGF-1 receptors, AMP-dependent kinase (AMPK), target-of-rapamycin (TOR), and lastly sirtuins to culminate in control of proteostasis, unfolded protein response (UPR), stem cell maintenance and stress resistance. Additionally, consequences of interfering with such ROS signals by pharmacological or natural compounds are being discussed, concluding that particularly antioxidants are useless or even harmful.
    Dose-Response 05/2014; 12(2):288-341. · 1.23 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Introduction: An increase in the oxidative stress and a decrease in the antioxidant levels have been described in diabetic patients, that have been related with the etiopathogenesis of diabetes and its chronic complications. Methods: We performed a non-systematic review to evaluate the relationship between oxidative stress and diabetes, and the possible effects of antioxidants in the prevention and treatment of diabetes and its complications. Results: The intervention studies including different antioxidants have not demonstrated any beneficial effect on cardiovascular and global morbimortality in different populations, including diabetic patients. Neither of these studies has demonstrated a beneficial effect of antioxidant supplementation on the prevention of diabetes. According to these studies, these substances can decrease lipid peroxidation, LDL-cholesterol particles oxidation and improve endothelial function and endothelial-dependent vasodilatation, without significant improvement in the metabolic control of these patients. Conclusions: The current evidence does not support the use of high doses of antioxidants on the prevention and treatment of diabetes and its complications.
    Nutricion hospitalaria: organo oficial de la Sociedad Espanola de Nutricion Parenteral y Enteral 02/2011; 26(1):68-78. · 1.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The present study was conducted to investigate the effect of -carotene on the antioxidant system of rats with diabetes. Forty Sprague Dawley rats were fed the AIN-76 control diet or the same diet supplemented with -carotene (7.2 mg/kg diet) for 3 weeks, then diabetes was induced in half the rats by administering streptozotocin (45 mg/kg BW) into the femoral muscle. Diabetic and normal rats were fed the experimental diets for 2 more weeks. To investigate the effect of dietary -carotene on diabetes, the activities of antioxidative enzymes and glutathione concentration were determined in normal and streptozotocin-induced diabetic rats. The plasma glucose levels in diabetic rats were not influenced by the dietary supplementation of -carotene. Hepatic activities of catalase and superoxide dismutase in diabetic rats were significantly lower than those of control rats but -carotene tended to induce these activities. Glutathione-S-transferase activity was not significantly different between experimental groups. Glucose-6-phosphatase activity was induced in diabetic rats, but dietary supplementation of -carotene reduced this activity. The hepatic concentration of reduced glutathione in diabetic rats was lower than that of control rats, but dietary supplementation with -carotene restored the content to some extent. These data suggest that diabetic rats are exposed to increased oxidative stress and that dietary supplementation with -carotene may reduce its detrimental effects.
    Journal of the Korean Society of Food Science and Nutrition 08/2011; 40(8).

Preview

Download
0 Downloads
Available from