Maternal BMI is positively associated with human milk fat: a systematic review and meta-regression analysis

Background: Lack of robust estimates of human-milk nutrient composition and influential maternal factors, such as body composition, are barriers to informing nutrition policies and programs. Objective: The objective was to understand the relation between maternal BMI and human-milk energy, fat, and/or total protein. Methods: Four electronic databases (MEDLINE, Embase, CINAHL, and Web of Science) were searched. Outcomes assessed were human-milk energy (kcal/L), fat (g/L), and total protein (g/L) from mothers 1 to 6 mo postpartum. Studies with data on maternal BMI or weight and height that quantified human-milk energy, fat, or protein between 1 and 6 mo postpartum were eligible. Random-effects meta-regression weighted by the inverse of the study-level SE was completed for each of the 3 outcomes. The certainty of evidence for each outcome was assessed using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Results: A total of 11,373 titles and abstracts were identified, and after full-text screening, 69 articles of 66 studies were included. Meta-regression results showed a positive association between maternal BMI and human-milk fat (beta: 0.56 g/L; 95% CI: 0.034, 1.1; P = 0.04; I-2 = 93.7%, n = 63 datapoints). There was no significant association between maternal BMI and human-milk energy (beta: 3.9 kcal/L; 95% CI: -1.6, 9.5; P = 0.16, I-2 = 93.3%, n = 40 datapoints) or total protein (beta: 0.13 g/L; 95% CI: -0.16, 0.41; P = 0.37, I-2 = 99.1%, n = 40 datapoints). The certainty of evidence for human-milk energy was low and the certainty of evidence for fat and total protein was very low. Conclusions: Meta-regression analysis of available literature suggested an association between maternal BMI and human-milk fat between 1 and 6 mo postpartum. Future studies are needed to confirm the relation between maternal BMI; variation in human-milk energy, fat, and protein content; and the implications for child growth and development.

Automated summary

The study aimed to understand the relation between maternal BMI and human-milk energy, fat, and total protein. It was found that there was a positive association between maternal BMI and human-milk fat, but no significant association with energy and total protein. The certainty of evidence for human-milk energy was low, while for fat and total protein it was very low.