Association between protein intake and risk of gestational diabetes mellitus: A systematic review and dose-response meta-analysis of cohort studies

Background: Gestational diabetes mellitus (GDM) is a common condition in pregnancy, the prevalence of which has increased. Identifying modifiable risk factors for GDM, such as dietary factors, could prevent or delay the onset of the condition. Our goal was to perform a comprehensive meta-analysis of cohort studies, to summarize the current evidence on the relationship between total, animal, and plant protein intake during pregnancy, as well as pre-pregnancy protein intake, and the risk of GDM. Methods: A literature search was completed using Scopus, PubMed, Web of Science, and Google Scholar up to January 2023 and references of retrieved relevant articles. Observational studies examining the association between the consumption of dietary protein from different sources in pre-pregnancy or/and during pregnancy and the risk of GDM were included. To combine effect sizes for the comparison between the highest and lowest categories of protein intake, a random effects model was utilized. Dose -response relationships were investigated using a 1 -stage random-effects model. Results: 8 observational studies were included in the systematic review and 5 prospective cohort studies in the meta-analysis, involving a total of 24,160 participants and 2450 cases of GDM. The analysis revealed a significant association between total protein intake during pregnancy and an elevated risk of GDM (relative risk (RR): 2.24, 95 % confidence interval (CI): 1.67-3.0 0, P = 0.000). Conversely, no significant association was found between total protein intake before pregnancy and the risk of GDM. Both animal protein intake before pregnancy (RR: 1.47, 95 % CI: 1.06-2.03, P = 0.021) and during pregnancy (RR; 2.31, 95 % CI: 1.43-3.73, P = 0.001) showed a significant association with GDM. Interestingly, there was no significant association between the consumption of plant protein both before and during pregnancy and the risk of GDM. Further analysis revealed that an additional 5 % energy from total protein and animal protein per day was associated with a 24 % and 32 % before and 114 % and 67 % increased risk of GDM during pregnancy respectively. Conclusion: In conclusion, consumption of animal protein and total protein before pregnancy is associated with an increased risk of GDM, although the association is not significant for total protein. Conversely, plant protein intake is linked to a decreased risk of GDM, however, the results are not significant. The intake of any protein type (plant/animal/total) during pregnancy is associated with an elevated risk of GDM, with this association being statistically insignificant for plant protein. Further cohort studies are required to validate the findings presented in this study. Registration: PROSPERO (CRD42023396215). (c) 2024 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.