Association between unhealthy plant-based diets and metabolic syndrome in adult men and women: a population-based study in South Korea

No studies have investigated the associations between established plant-based diet indices and metabolic syndrome (MetS). We evaluated the associations between an overall plant-based diet index (PDI), healthy plant-based diet index (hPDI), unhealthy plant-based diet index (uPDI), and MetS in a nationally representative sample using data from 14,450 Korean adults (≥19y) in the Korea National Health and Nutrition Examination Survey 2012-2016. Dietary intakes were assessed by a semi-quantitative food frequency questionnaire. In the PDI, all plant foods received positive scores. In the hPDI, only healthy plant foods received positive scores. In the uPDI, only unhealthy plant foods received positive scores. All indices reverse scored animal food intake. Multivariable logistic regression models were used to examine the associations between three PDIs and MetS by sex, adjusting for potential risk factors. A total of 23.3% of Korean adults had MetS. In the overall population, individuals in the highest quintile of uPDI had greater odds (odds ratio: 1.54, 95% confidence interval: 1.28, 1.86, P-trend<0.001) of MetS than those in the lowest quintile. Higher uPDI score was associated with higher odds of hypertriglyceridemia in men, and abdominal obesity, high fasting glucose, and hypertriglyceridemia in women. No significant associations were observed between PDI, hPDI, and MetS. Greater adherence to unhealthy plant-based diets was associated with greater odds of MetS and its components suggesting the importance of the quality of plant-based diet in South Korean adults. Sex difference may be considered when recommending plant-based diets for prevention and management of metabolic diseases.