Anthropology & Human Biology, Indiana University
Friday 8:45-9:00, Galleria South
The relationship between childhood diets and age at menarche has long been of interest, especially as they contribute to overall energy balance or macronutrient intake. Here I consider how a particular food, cow milk, might affect age at menarche. While the contribution of any one type of food to sexual maturation is likely to be slight, there is reason to believe that milk might be an exception. Mammalian milk is produced to support the growth and development of infants, yet among humans, consumption is both of milk from another species with a more rapid rate of growth and development and, for many, it continues well beyond the traditional age at nursing. Thus this pattern of milk consumption may influence life history parameters. Among the components of milk that might influence age at menarche, beyond calories and overall protein, is insulin-like growth factor I (IGF-I). Circulating levels of IGF-I increase with milk consumption, and IGF-I is a potent mitogen. IGF-I levels surge during pubertal development, and hence IGF-I is a candidate biomarker linking milk consumption to sexual maturation in girls. This paper uses data from the National Health and Examination Survey 1999-2004 to evaluate whether milk consumption during childhood is associated with age at menarche or the risk of early menarche after controlling for overall energy and macronutrient intake. This will allow an assessment of whether milk in the diet has some unique associations with sexual maturation in girls independent of its contribution to energy budgets, macronutrient status, or linear growth.