The association between dietary protein and gallstones in adults under 60 years old: A cross-sectional study.

Although there is a clear association between dietary composition and risk factors such as obesity and insulin resistance, the link between protein intake and gallstones remains unclear. The aim of this study is to investigate the association between dietary protein and the development of gallstones in American adults under 60 years old. The study employed weighted multivariate logistic regression, and smoothed curve fitting to examine the association between dietary protein and gallstones using data from National Health And Nutrition Examination Survey from 2017 to 2020. To correct for the skewed distribution of protein intake, the data underwent Box-Cox transformation. Among the 3150 participants aged 20 years and older, there was a significant negative association between Box-Cox-transformed protein intake and gallstone incidence for the United States adults under 60 years old. The risk of gallstones was reduced by 30 percent for each unit of Box-Cox-transformed dietary protein intake. The group with the highest protein intake had a 76% lower risk of gallstones compared to the group with the lowest protein intake. Threshold effect analysis revealed that the optimal threshold identified by the model was 9.79; when protein intake was below this threshold, each unit increase in intake was significantly associated with a 27% reduction in the risk of gallstones; once this threshold was exceeded, this association was no longer significant. Among adults under the age of 60 in the United States, there is an inverse association between dietary protein intake and gallstones. After Box-Cox transformation, the optimal threshold for dietary protein intake was 9.79, when protein intake exceeded this threshold, its risk-reducing effect was no longer statistically significant.