Increased antioxidant intakes may reduce risk of metabolic syndrome

Low serum concentrations of antioxidants seem to be associated with metabolic syndrome, a new US study indicates.

The study analyzed data from recent national surveys (e.g., NHANES 2001–2006) on U.S. adults aged 20 to 85 years to examine the association between serum antioxidant status and metabolic syndrome (1). The study results showed that adults with metabolic syndrome had consistently lower serum carotenoid (beta-carotene, lutein and zeaxanthin) concentrations compared with those without metabolic syndrome, even after correcting for potential confounders. While vitamin C exhibited a similar association, high vitamin A concentrations were related to low incidences of metabolic syndrome, but only among men. Vitamin E showed no significant relationship with metabolic syndrome.

The researchers commented that these findings add to the accumulating evidence that a higher level of oxidative stress can contribute to the development of the metabolic syndrome, a combination of medical disorders (e.g., insulin resistance, obesity and hypertension), that increase the risk of developing cardiovascular disease and diabetes. Future intervention studies of dietary and lifestyle change would be necessary 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 diseases.

Previous observational studies (2, 3) and randomized controlled trials (4) consistently found an association between increased risks of type 2 diabetes or metabolic syndrome and low carotenoid levels. However, intervention trials did not find any long-term benefits of dietary supplements, particularly with single antioxidants, in the prevention of metabolic syndrome. The failure of single antioxidants to reduce disease risk may be explained, at least in part, by findings indicating that some dietary antioxidants seem to synergistically network against oxidative stress and influence each other’s blood levels (5).

1. Beydoun M. A. et al. Serum antioxidant status is associated with metabolic syndrome among U.S. adults in recent national surveys. The Journal of Nutrition. 2011.
2. Coyne T. et al. Metabolic syndrome and serum carotenoids: findings of a cross-sectional study in Queensland, Australia. Br J Nutr. 2009; 102:1668–1677.
3. Ford E. S. et al. The metabolic syndrome and antioxidant concentrations: findings from the Third National Health and Nutrition Examination Survey. Diabetes. 2003; 52:2346–2352.
4. Czernichow S. et al. Effects of long-term antioxidant supplementation and association of serum antioxidant concentrations with risk of metabolic syndrome in adults. Am J Clin Nutr. 2009; 90:329–335.
5. Valtuena S. et al. The total antioxidant capacity of the diet is an independent predictor of plasma beta-carotene. Eur J Clin Nutr. 2007; 61:69–76.