Objectives: Metabolic syndrome is a cluster of risk factors for cardiovascular disease and type 2 diabetes, constituting a global public health problem. Lifestyle is a key factor in the development and management of metabolic syndrome; in particular, healthy diet and physical activity are suggested to be their critical components. A recent study suggests that the effect of exercise on metabolic syndrome may be enhanced by sufficient plasma vitamin C levels. Thus, we examined the combined effect of physical activity and dietary vitamin C on the risk of metabolic syndrome in the general Korean population.

Methods: In this population-based cross sectional study, we analyzed data from 22671 adults aged 20 years or older from the Korean National Health and Nutrition Examination Survey 2008-2012. Physical activity was measured using International Physical Activity Questionnaire, and we also computed as the total metabolic equivalent (METs-hr/week) summed from MET scores of walking, moderate activity, and vigorous activity. Vitamin C intake data used from a 24-hour dietary recall. We also classified participants into combined four groups based on median values of physical activity and vitamin C intake.

Results: The odds ratio (OR) for metabolic syndrome in individuals with both high physical activity and vitamin C intake (vs. both low physical activity and vitamin C intake) was 0.79 (95% confidence interval (CI), 0.71-0.88) after adjustment for potential confounding factors. The estimated combined effect was more than either high physical activity alone (OR, 0.81 (95% CI, 0.73-0.90)) or high vitamin C intake alone (OR, 0.89 (95% CI, 0.80-0.99)), although each of those was beneficial.

Conclusions: We found that physical activity and diet rich in vitamin C were associated with a lower risk of metabolic syndrome. Our findings also suggest that a combination of getting enough physical activity and eating a diet rich in vitamin C may be more beneficial strategy to effectively prevent metabolic syndrome.