Dietary Protein to Carbohydrate Ratio and Incidence of Metabolic Syndrome in Korean Adults Based on a Long-Term Prospective Community-Based Cohort

Interest in high protein diets has recently been increasing for reduction of weight or management of cardiometabolic risks. However, studies on high protein, low carbohydrate diet in Asians are limited. This study aimed to estimate whether the dietary ratio of protein (%) to carbohydrate (%) from total energy intake (p/c ratio) is associated with the risk of metabolic syndrome (MS) and its components in Korean adults using a long-term prospective cohort. A total of 6335 participants from the Korean Genome and Epidemiology Study, aged between 40 and 69 years, with no previous diagnosis of MS, cardiovascular diseases, or cancer at baseline (2001-2002) were followed until 2013. Dietary intake was measured using a validated semiquantitative food-frequency questionnaire. MS components were measured at baseline and every 2 years. During a mean of 7.7 years of follow up, 1198 (36.1%) men and 1169 (38.8%) women developed MS. The multivariate adjusted hazard ratio (HR) of incident MS was 1.43 (95% confidence interval, 1.09-1.89) for the highest compared lowest quintile of p/c ratio in men. When evaluating each component of MS, higher dietary p/c ratio was associated with an increased risk of high triglyceride and fasting glucose in men (HR for fifth vs. first quintile, 1.39 and 1.41 in Model 3, respectively). However, we observed no associations with incident MS and its components and dietary p/c ratio in women. In conclusion, we found that high dietary p/c ratio was associated with an increased risk of MS and its components (i.e., increased triglycerides and fasting glucose) in men. Our study suggested that even if the absolute amount of protein intake is not large, an increased p/c ratio may increase the risk of metabolic diseases.