A Scoping Review of Methodologies Exploring Diet and Health Outcomes in Lactating Women: What Has Been Done and Where to Next?

Developing dietary guidelines for lactating women presents significant challenges, due to limited evidence being available on their specific nutrient needs and the biological impacts of various dietary dimensions. Current dietary recommendations often rely on data from nonlactating women, leading to potential inaccuracies. The relationship between diet and health outcomes in lactating women remains underexplored, particularly across different dietary dimensions, such as nutrients, food groups, dietary patterns, and other specific dietary variables. The aims of this scoping review were to map the diverse methodologies employed in research into maternal diet during lactation, to identify the current gaps, and to suggest areas for future investigation. The review focused on the dietary variables studied in relation to breastfeeding outcomes, and offers insights into the current state of lactation nutrition research. A comprehensive search was conducted in the CINAHL, MEDLINE, and Embase databases up to December 13, 2022. The included studies encompassed original quantitative research on dietary intake among lactating women and any associated outcomes. Data extracted included study characteristics, dietary variables, and outcome measures, and they were analyzed using descriptive statistics and pivot tables. Of the 1666 relevant studies identified, 231 met the inclusion criteria. Most research was conducted in high-income and upper-middle-income countries. Studies mainly focused on relatively short lactation durations, nutrient-based dietary dimensions, and maternal outcomes, particularly breast milk composition. Maternal metabolic status and child outcomes, such as infant micronutrient status and longitudinal growth, were underexplored. Specific dietary variables included meal frequency and nutrient intake from various food sources. Commonly adjusted covariates were maternal age and socio-economic status, while contraceptive use and sanitation were often overlooked. Many areas of research concerning the diet-health relationship in lactating women remain unexplored. Filling these gaps will gather evidence to inform the development of dietary guidelines for this population.