Impact of Maternal Dietary Intake on Breast Milk Composition and Infant Nutrition Status Among Lactating Women in Nyeri County, Kenya
Kiboi, Willy Kahanya
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Exclusive breastfeeding for the first six months of life, with continued breastfeeding up to 2 years after the introduction of complementary feeds, is considered as the standard norm for infant feeding. Although the benefits of breastfeeding have long been known, studies on the composition of human milk are still ongoing. Considering that breast milk is the sole source of the nutrition for the infant in the first six months of life, it is essential to have accurate and up to date data on its composition. The composition of human milk could vary according to many maternal factors such as diet, nutritional status, genetics and environmental exposures, among other factors. The amount of variability in human milk composition that could be attributed to maternal dietary intake remains largely unknown. In Africa, particularly in Kenya, there is scanty information available on the nutrient composition of breast milk and the factors that affect its composition. This study therefore investigated the association between maternal dietary intake with breast milk nutrient composition and their effect on the nutrition status of the infant (under six months). The longitudinal study was conducted in Nyeri County, Kenya. Participants included lactating mothers with infants under six months. The lactating mothers’ dietary intake, nutrition status (BMI, MUAC and serum micronutrients) and that of their infants (recumbent length and weight) were assessed. Additionally, breast milk samples were collected and analyzed for selected nutrient content and correlated with both maternal dietary intake and the infant’s nutritional status. The breast milk samples were analysed for energy, macronutrients and selected micronutrients (vitamin A, calcium, magnesium, zinc and iron). All the measurements were done at two time points (first and the fifth month of lactation) among a comprehensive sample of 104 mother-child dyads. Significant changes in the mean nutrient composition were noted between the first and fifth month of lactation (protein-0.96 g/dL and 0.85 g/dL, p = 0.03; vitamin A-22.48 and 31.61 μg/dL, p value, p < 0.001; iron-0.39 mg/L and 0.47 mg/L, p = 0.02). There was statistically significant (p < 0.05) relationship between mother energy intake with milk lactose (r = 0.30); carbohydrate intake with milk true proteins (r = 0.24); protein intake with milk true protein (r = 0.44) and milk iron (r = 0.31); fat intake with milk energy (r = 0.29), milk true protein (r = 0.40) and milk fat (r = 0.35); percent of energy from fat with milk energy (r = 0.39) and milk fat (r = 0.45). Furthermore, vitamin A intake with milk retinol (r = 0.56), calcium intake with milk zinc (r = -0.32) and iron (r = -0.27), zinc and iron (r = -0.26). For maternal nutrition status, hemoglobin (Hb) was correlated with both milk energy (r = 0.30) and true protein (r = 0.44). Serum retinol, magnesium and iron were correlated with milk retinol (r = 0.34), magnesium (r = 0.29) and iron (r = 0.33), respectively. Association between breast milk nutrient composition and infant nutrition status revealed that the milk true protein (r = 0.58) and retinol (r = 0.32) were positively correlated with weight for age and MUAC (r = 0.31) of the infant. Weight for length was also positively correlated with milk lactose (r = 0.47). No relationship was found between other maternal factors (age, parity, child sex and mode of delivery) and any of the selected breast milk nutrient content (p > 0.05). The study observes that breast milk nutrient composition is variable over the course of lactation. Further, both maternal dietary intake and nutrition status (serum micronutrient status) are associated with the nutrient composition of human milk. Moreover, breast milk nutrient composition is related to the infant nutrition status. Promoting adequate nutrient intake and optimal maternal nutritional status during lactation is essential to ensure adequate child growth and development.