Association between protein intake and sources in mid-pregnancy and the risk of gestational diabetes mellitus.

Objectives: This study aimed to investigate the relationship between dietary protein intake and sources in the second trimester of pregnancy and the risk of gestational diabetes mellitus (GDM) and to further investigate the effects of total protein and animal protein intake on the risk of GDM.

Methods: A case-control study was conducted, which involved 947 pregnant women in the second trimester from three hospitals in Jiangsu, China. Dietary intake was assessed using a 3-day 24-hour dietary recall and a food frequency questionnaire. Two models (leave-one-out and partition models) in nutritional epidemiology were used for substitution analysis, and logistic regression was performed to explore the relationships, adjusting for multiple confounding factors.

Results: After adjusting for confounding factors, total protein intake was negatively correlated with GDM risk (OR [95% CI], 0.10 [0.04-0.27]; P<0.001). Animal protein also negatively correlated with GDM risk, but this became insignificant when total calorie, carbohydrate and fat intake were added as covariates to the analysis (0.68 [0.34-1.34]; P = 0.263). No association was found between plant protein and GDM(1.04 [0.69-1.58]; P = 0.852). Replacing carbohydrates with an equal energy ratio(5% of total energy intake) of total protein, animal protein and plant protein respectively reduced the risk of GDM by 45%, 46% and 51%.

Conclusions: The intake of total protein and animal protein, especially eggs, dairy products, and fish, can reduce the risk of GDM while consuming unprocessed red meat increases the risk. There is no significant association between the intakes of plant protein, processed meat, and poultry meat and the occurrence of GDM. The results of this study are expected to provide a basis for precise nutritional education, health guidance during pregnancy, and early prevention of GDM.