title: Vitamin A dynamics in breastmilk and liver stores: a life history perspective.
abstract: OBJECTIVE
  Newborns are dependent on breastmilk vitamin A for building hepatic stores of vitamin A that will become critical for survival after weaning. It has been documented that vitamin A concentrations in breastmilk decline across the first year postpartum in both well-nourished and malnourished populations. The reason for this decline has been assumed to be a sign of concurrently depleting maternal hepatic stores. This study investigates this assumption to clarify why the decline occurs, drawing on life history theory.
  
  
  METHODS
  A cross sectional survey was conducted among lactating mothers in Kenya in 2006. Data were used to examine (1) the relationship between liver vitamin A and time, (2) if the relationship between milk and liver vitamin A varies by time, and (3) by maternal parity.
  
  
  RESULTS
  The relationship between liver vitamin A and time fits the quadratic pattern with marginal significance (P = 0.071, n = 192); the liver vitamin A declined during early postpartum then recovered in late postpartum time, controlling covariates. The milk-liver vitamin A relationship varied by postpartum time periods (P = 0.03) and by maternal parity (P = 0.005). Mothers in earlier postpartum or higher parity had a stronger positive relationship between milk and liver vitamin A than mothers in later postpartum or lower parity.
  
  
  CONCLUSIONS
  Our observations are consistent with life history tradeoffs and negate the assumption that maternal hepatic and milk vitamin A decline together. Rather, maternal liver vitamin A has a dynamic relationship with milk vitamin A, particularly depending on postpartum time and maternal parity.
authors.affiliation: Department of Anthropology, Michigan State University, East Lansing, Michigan, USA. masakof@msu.edu
authors.forename: Masako
authors.initials: M
authors.lastname: Fujita
authors.forename: Bettina
authors.initials: B
authors.lastname: Shell-Duncan
authors.forename: Philip
authors.initials: P
authors.lastname: Ndemwa
authors.forename: Eleanor
authors.initials: E
authors.lastname: Brindle
authors.forename: Yun-Jia
authors.initials: YJ
authors.lastname: Lo
authors.forename: Yeri
authors.initials: Y
authors.lastname: Kombe
authors.forename: Kathleen
authors.initials: K
authors.lastname: O'Connor
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007630:Kenya; D008099:Liver / Q000737:chemistry*; D008895:Milk, Human / Q000737:chemistry*; D008954:Models, Biological; D010298:Parity; D049590:Postpartum Period; D011247:Pregnancy; D013997:Time Factors; D014801:Vitamin A / Q000032:analysis* / Q000097:blood
chemical_list: D014801:Vitamin A