This dissertation research concerns the intergenerational predictors of breast milk characteristics and infant growth in a Philippine women. Past work has shown that maternal investment of nutrients in offspring in utero is conditioned by a woman's own early life nutritional experiences, with women better-nourished as fetuses giving birth to larger offspring. This study will investigate whether a woman's early life nutritional experiences continue to influence nutrient transfer after birth, as reflected in the composition of breast milk that she produces and in the growth rate of her offspring. An ability to adjust investment in offspring in response to prior nutritional experiences could serve an adaptive function by allowing offspring growth rate to be set to match local nutritional availability. In addition, it is now known that mode of infant feeding and diet composition can have lasting effects on adult risk for diseases like diabetes.
To clarify these issues, this study has the following aims: 1) document natural variation of milk macronutrients; 2) investigate the association between a woman's early life nutrition and growth and the composition of milk that she produces as an adult; 3) explore the possible influences of milk composition on the growth and body composition of her offspring. These objectives will be addressed in collaboration with a study that has followed a large sample of women and their offspring living in Cebu City (the Philippines) since 1983. Detailed health, nutrition, and anthropometric data have been collected on all participants at regular intervals, starting with bi-monthly interviews during the first two years of life. As these original offspring are now beginning their own reproductive careers, this study will identify new pregnancies and follow up their newborns, collecting nutritional, behavioral, anthropometrics and breast milk samples at two, four and six months of life. Milk will be analyzed for nutritional composition. The associations of current diet, activity, and body composition with variation in milk composition, and the possible influence of early life nutrition and growth velocity, will be modeled using multivariate statistical techniques.
This study's primary intellectual merit is in expanding understanding of the natural complexities and determinants of human milk variation, while testing ideas about the adaptive and evolutionary significance of that variation. Specifically, it will explore the possible role of variation in milk composition as a source of intergenerational "information" about the mother's chronic or early life nutritional experiences. Because the flow of nutrients to offspring influences offspring growth rate and the adult phenotype, this sensitivity to the mother's prior experiences could increase the phenotypic "fit" with the environment.
The broader impacts of this study include training a graduate student, and contributions to public health. Diet and lifestyle are being transformed globally, with resulting increases in obesity and Type II diabetes in individuals who were malnourished or stunted as infants. Breast feeding and milk composition have been shown to predict future disease risk. This study will illuminate these issues by exploring how milk variation arises and what effects it has on offspring growth.
