The relation of dietary protein intake before and during the pregnancy with gestational diabetes mellitus (GDM): A GRADE-assessed systematic review and dose-response meta-analysis of epidemiologic studies.

Background: Although previous studies investigated the relation of protein intake and gestational diabetes mellitus (GDM), their findings were controversial. Therefore, we aimed to summarize this association, through a comprehensive systematic review and dose-response meta-analysis.
Methods: Electronic databases including MEDLINE (PubMed), ISI Web of Science, Scopus and motor engineering of Google Scholar were systematically searched up to April 2023. Observational studies which investigated odds of GDM in relation to protein intake were included.
Results: A total of 31,005 participants with 3451 cases of GDM from 13 eligible investigations were included in the systematic review and meta-analysis. Comparing the highest and lowest intakes of total, animal, and plant proteins revealed the summary RRs of 1.82 (95% CI: 1.42, 2.33), 1.79 (95% CI: 1.50, 2.14), and 0.98 (95% CI: 0.81, 1.20), respectively, indicating a significant positive association between total and animal protein intake and GDM. In the dose-response analyses, each 5% increment in energy intake from total protein during pregnancy was related to 20% increased odds of GDM (RR = 1.20; 95% CI: 1.09, 1.33). In the non-linear dose-response analyses, we found a non-linear association for animal protein intake during pregnancy (P for non-linearity <0.001); so that, a risk increase was seen from zero to 10% of energy intake from animal proteins, however, a risk reduction was seen after 10% of energy intake. However, there was not any significant non-linear trend between plant protein intake during pregnancy and risk of GDM. Based on the GRADE assessment, the quality of evidence for total, animal and plant protein was rated as "moderate", "moderate" and "very low", respectively.
Conclusion: We found a significant positive association between total protein intake and GDM; however, the associations of animal and plant protein intake with GDM were dose-dependent.
Competing Interests: Conflicts of interest None of the authors had any personal or financial conflicts of interest.
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