Mediating effects of metabolic factors on the association between fruit or vegetable intake and cardiovascular disease: the Korean National Health and Nutrition Examination Survey

OBJECTIVE We assessed the mediating effects of metabolic components on the relationship between fruit or vegetable intake and cardiovascular disease (CVD). DESIGN Cross-sectional study. SETTING This study was conducted using data from the 2013-2015 Korean National Health and Nutrition Examination Survey, which is a national representative cross-sectional survey to assess health and nutritional status in the Korean population. METHOD AND ANALYSIS A total of 9040 subjects (3555 males and 5485 females) aged ≥25 years were included in the study. Physician-diagnosed CVD via self-report was used as the outcome. Fruit or vegetable intake was measured via a dish-based semiquantitative food frequency questionnaire and grouped into categories (<1 time/day, 1 time/day, 2 times/day and ≥3 times/day). Systolic blood pressure (SBP), cholesterol and fasting glucose were considered metabolic mediators, and the bootstrap method was used to assess mediating effect. RESULTS About 1.8% of adults aged 25-64 years had CVD. According to the result of 'process' macro, the confounder-adjusted risk for CVD decreased by 14% (OR=0.86, 95% CI 0.74 to 0.98) as fruit, but not vegetable, intake was increased by one unit per day. After additional adjustment for three metabolic factors simultaneously, the OR was attenuated to 0.89 (95% CI 0.77 to 1.03). This result indicates that the indirect effect of three metabolic factors accounted for 21.4% of the relationship between fruit intake and CVD. SBP was a more important metabolic mediator than the other factors. The indirect effect by metabolic factors accounted for 30.0% when body mass index was additionally controlled as a mediator, and SBP still had an independent effect compared with the other mediators. CONCLUSIONS Our results indicate that controlling SBP may lessen the CVD risk, and a diet rich in fruits can regulate SBP which, in turn, reduces CVD risk.