Metabolic syndrome and serum carotenoids: findings of a cross-sectional study in Queensland, Australia.

Several components of the metabolic syndrome, particularly diabetes and CVD, are known to be oxidative stress-related conditions and there is research to suggest that antioxidant nutrients may play a protective role in these conditions. Carotenoids are compounds derived primarily from plants and several have been shown to be potent antioxidant nutrients. The aim of the present study was to examine the associations between metabolic syndrome status and major serum carotenoids in adult Australians. Data on the presence of the metabolic syndrome, based on International Diabetes Federation 2005 criteria, were collected from 1523 adults aged 25 years and over in six randomly selected urban centres in Queensland, Australia, using a cross-sectional study design. Weight, height, BMI, waist circumference, blood pressure, fasting and 2 h blood glucose and lipids were determined, as well as five serum carotenoids. Mean serum alpha-, beta-carotenes and the sum of the five carotenoid concentrations were significantly lower (P < 0.05) in persons with the metabolic syndrome (after adjusting for age, sex, education, BMI status, alcohol intake, smoking, physical activity status and vitamin/mineral use) than persons without the syndrome. alpha-, beta- and total carotenoids also decreased significantly (P < 0.05) with increased number of components of the metabolic syndrome, after adjusting for these confounders. These differences were significant among former smokers and non-smokers, but not in present smokers. Low concentrations of serum alpha-, beta-carotenes and the sum of five carotenoids appear to be associated with metabolic syndrome status. Additional research, particularly longitudinal studies, may help to determine whether these associations are causally related to the metabolic syndrome, or are a result of the pathologies of the syndrome.