Association between dietary protein intake and depression in American adults with metabolic syndrome

Abstract

Background There is currently intense interest in the effects of macronutrients on mental disorders. The purpose of the study was to analyze the relationship between depression and protein intake in people with metabolic syndrome. Methods The study analyzed data on 7922 individuals with metabolic syndrome that were derived from the National Health and Nutrition Examination Survey (NHANES)1999–2018. To test whether the investigated variables differed significantly, variance and the chi-squared test were used to analyze dietary protein intake among groups. Variables with significant differences were selected for multiple logistic regression analysis to further explore the associations between PHQ-9 defined depressive symptoms and protein. Smoothed curve fitting was employed to determine whether if there was a nonlinear correlation between the two. Results As protein eaten increased, the number of participants suffering from depression decreased. After adjusting for confounding variables (eGFR, cancer, thyroid disease, total energy, carbohydrate, fiber, calcium, caffeine intake, magnesium, and general information), multivariate logistic regression analysis indicated that dietary protein may serve as a protective factor for depression. Moreover, a negative nonlinear association between depression and dietary protein was found. Conclusion These findings indicate that for individuals with metabolic syndrome dietary protein is relevant to depression.