A report published online on March 30, 2011 in the Journal of Nutrition reveals the results of a large study of adult Americans which found a lower risk of metabolic syndrome (a cluster of risk factors that increase the risk of developing diabetes and/or cardiovascular disease), among those with higher serum levels of vitamin C and carotenoids.
May A. Beydoun of the National Institute on Aging and her associates evaluated data from up to 11,845 participants in the National Health and Nutrition Examination Survey 2001-2006, which included men and women aged 20 to 85 residing in the United States. Anthropometric measurements and blood pressure were assessed upon enrollment, and blood samples were analyzed for the antioxidant nutrients retinol, retinyl esters, carotenoids (which include alpha and beta carotene, beta-cryptoxanthin, lutein plus zeaxanthin, and lycopene), vitamin C and vitamin E, as well as glucose, lipids, C-reactive protein and other factors.
Thirty-two percent of the male and 29.5 of the female subjects were classified as having metabolic syndrome by exhibiting three of the following criteria: abdominal obesity defined by waist circumference greater than or equal to 40 inches in men and 35 inches in women, triglycerides greater than or equal to 150 milligrams per deciliter, HDL cholesterol of less than 40 milligrams per deciliter for men and 50 milligrams per deciliter for women, blood pressure greater than or equal to 130/85 mmHg, and fasting plasma glucose greater than or equal to 100 milligrams per deciliter. Participants with metabolic syndrome had significantly lower serum 25-hydroxyvitamin D and higher total homocysteine levels. Having higher serum carotenoids or vitamin C was associated with a lower adjusted risk of metabolic syndrome in men and women, while retinol and retinyl esters were associated with a protective effect only in men. Higher serum retinol and retinyl esters also appeared to be protective against inflammation, as indicated by decreased C-reactive protein levels.
"It is clear from previous studies that oxidative stress is associated with incidence of type 2 diabetes and cardiovascular mortality and morbidity," the authors write. "Our study adds to the accumulating evidence that a higher level of oxidative stress also accompanies obesity-related disorders, which may be the causative agent behind further complications related to metabolic syndrome, including the development of atherosclerosis."
"Future intervention studies of dietary and lifestyle change must be conducted to assess the utility of modifying serum antioxidant concentrations, especially carotenoids, given their suboptimal levels among U.S. adults with metabolic syndrome, for the prevention of type 2 diabetes and various cardiovascular endpoints," they conclude.