April 5, 2011

Greater levels of some antioxidants associated with lower risk of metabolic syndrome

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.

Diabetes

It is crucial that diabetics (and those predisposed to diabetes) understand the ways in which blood glucose causes damage and take active steps to interrupt these processes. The most notorious process is glycation, the same process that causes food to brown in an oven. Glycation (defined as sugar molecules reacting with proteins to produce nonfunctional structures in the body) is a key feature of diabetes-related complications because it compromises proteins throughout the body and is linked to nerve damage, heart attack, and blindness.

Oxidative stress is also central to the damage caused by diabetes. Diabetics suffer from high levels of free radicals that damage arteries throughout the body, from the eyes to the heart. It is important that diabetics understand their need for antioxidant therapy to help reduce oxidative stress and lower the risk of diabetic complications.

Oxidative stress in diabetes is also linked to endothelial dysfunction, the process that characterizes atherosclerotic heart disease. According to studies, diabetes encourages white blood cells to stick to the endothelium, or the thin layer of cells that line the inside of arteries. These white blood cells cause the local release of pro-inflammatory chemicals that damage the endothelium, accelerating atherosclerosis (Lum H et al 2001). Diabetes is closely associated with severe coronary heart disease and increased risk of heart attack.

Several preclinical studies evaluated vitamin C’s role during mild oxidative stress. The aqueous humor of the eye provides surrounding tissues with a source of vitamin C. Since animal studies have shown that glucose inhibits vitamin C uptake, this protective mechanism may be impaired in diabetes (Corti A et al 2004). Supplementation with antioxidant vitamins C and E plays an important role in improving eye health (Peponis V et al 2004). High vitamin C intake depresses glycation, which has important implications for slowing diabetes progression and aging (Krone CA et al 2004).

Vitamin C also has a role in reducing the risk of other diabetic complications. In one clinical study, vitamin C significantly increased blood flow and decreased inflammation in patients with both diabetes and coronary artery disease (Antoniades C et al 2004). Three studies suggest that vitamin C, along with a combination of vitamins and minerals (Farvid MS et al 2004), reduces blood pressure in people with diabetes (Mullan BA et al 2002) and increases blood vessel elasticity and blood flow (Mullan BA et al 2004).

Life Extension Update

• High antioxidant diet improves insulin sensitivity in obese men and women
• Vitamin C deficiency linked to metabolic syndrome components in young adults

What's Hot

• Meta-analysis affirms protective effect of Mediterranean diet against metabolic syndrome components
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Life Extension Magazine®

• Metabolic syndrome: the twenty-first century epidemic
• Phenotypic nutrition: a new strategy for preventing metabolic syndrome

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