three-part Developments in the Field of Nutrition systematic review reveals much we still don’t know
The World Health Organization (WHO) recommends exclusive breastfeeding for the first six months and continuing breastfeeding as part of the baby’s nutrition until at least two years of age. The positive growth and development outcomes observed in breastfed infants according to WHO guidelines may be partly attributable to the array of nutritional and non-nutritional components of breast milk. On the other hand, inadequate breastfeeding, especially in the first six months of life, can result in the death of up to 1.4 million children annually, accounting for an estimated 10% of the total burden of childhood diseases worldwide.
Although there has been a marked increase in breast milk research in recent years, there are still large gaps in our understanding of how breast milk components affect childhood growth and development. However, as technology has advanced, there has been increasing pressure to expand the scope and breadth of existing research, moving beyond individual nutrient analysis to investigate various breast milk components and their associated combined clinical outcomes among children.
“Human Milk Composition and Child Growth and Body Composition in the First 2 Years: A Systematic Review,” published on: Developments in the Field of Nutritionexplores the available evidence that will help us better understand the link between human milk constituents and growth and body composition during the first two years of life. Due to the large number of research studies in this field, the results are organized into three articles divided into (1) human milk macronutrients, (2) human milk micronutrients, and (3) human milk biologically active (bioactive) components.
This Supplement is free to view. Readers can access all three articles regardless of subscription status.
The authors of this three-part review are Dr. James, a Canadian Tier 2 Research Chair in Early Nutrition and the Developmental Origins of Health and Disease, funded by the Bill & Melinda Gates Foundation. It is part of the International Milk Compounding Consortium, led by Meghan Azad. The International Milk Composition Consortium was founded in 2020 to develop an effective, harmonized approach to breast milk research and analysis by bringing together maternal-child health and breast milk researchers with statistical experts. Among the authors are Dr. It features Meredith Brockway and ASN members Lindsay H. Allen, Daniela Hampel and Sarah M. Reyes.
Below is a brief summary of the key findings from each of the three papers:
Human Milk Macronutrients and Child Growth and Body Composition in the First 2 Years: A Systematic Review
The macronutrients in human milk are well researched. However, their relationship to growth and body composition in early life is still poorly understood. In response, the authors of this review systematically searched the scientific literature, leading them to 57 studies collected from 5,979 mother-infant dyads that investigated the relationship between macronutrients in breast milk and infant growth and body composition. The authors found that overall, “digestible carbohydrates were positively associated with infant weight outcomes.” Moreover, “protein was positively associated with infant length, but no association was reported for infant weight.” Interestingly, “human fat was not consistently associated with any infant growth measures.” The authors noted that their ability to reach strong conclusions was limited by differences in study design and underreporting of results. Going forward, the authors urge researchers to “accurately record and account for the privilege of breastfeeding; use consistent sampling protocols that account for temporal variation in human milk macronutrients; and use reliable, sensitive and accurate techniques for human milk macronutrient analysis.”
Human Milk Micronutrients and Child Growth and Body Composition in the First 2 Years: A Systematic Review
Micronutrients play a critical role in children’s growth and development. Although it is well documented that deficiencies in some micronutrients, such as zinc, iron, and vitamin A, can lead to poor growth in childhood, information on specific relationships between breast milk micronutrients and infant and child growth is lacking. Specifically, “this systematic review reveals that little is known about how individual human milk micronutrients affect infant and young child anthropometry.” The authors noted that data were sparse for many micronutrients. Moreover, despite the WHO recommendation to breastfeed for at least two years or longer, most studies have focused on the first six months of life. However, the authors observed that “available evidence suggests a positive correlation between infant growth and concentrations of iodine, manganese, calcium, and zinc in breast milk.” But the authors cautioned that even these relationships “remain largely unclear due to sparse data, small sample sizes, and methodological limitations of existing studies.”
Bioactive Components of Human Milk and Child Growth and Body Composition in the First 2 Years: A Systematic Review
Non-nutritional human milk bioactives, including hormones, breast milk oligosaccharides, and immunomodulatory components, may have a long-term impact on the infant’s microbiome, immune function, and growth and development. While infant formula can potentially provide nutrients found in human milk, it does not replace many of the critical non-nutritive breast milk bioactives. The largest body of evidence among these bioactive components in human milk shows an inverse relationship between concentrations of the hormones leptin and adiponectin and infant growth, although not all studies agree. But overall, this systematic review “revealed inconsistent relationships between bioactive constituents in human milk and body composition in the infant’s first 2 years.” Moreover, it “highlighted inconsistent data collection methods and identified many knowledge gaps for future research.” The authors believe that “future research should ideally capture human milk intake, use biologically relevant anthropometry and integrate components across categories, adopting a systems biology approach to better understand how human milk components work independently and synergistically to influence infant growth.”
To gain a deeper understanding of the relationship between the components of breast milk and childhood growth and development, we invite you to review this three-part systematic review in its entirety. The authors can also direct you to areas where more research is needed to improve infant and child health.
