Conflict or congruence? Maternal and infant-centric factors associated with shorter exclusive breastfeeding durations among the Tsimane

Abstract

Six months of exclusive breastfeeding (EBF) is considered optimal for infant health, though globally most infants begin complementary feeding (CF) earlier—including among populations that practice prolonged breastfeeding. Two frameworks for understanding patterns of early CF emerge in the literature. In the first, maternal and infant needs trade-off, as “maternal-centric” factors—related to time and energy demands, reproductive investment, cultural influences, and structural barriers— favor supplanting breastfeeding with earlier and increased CF. A second framework considers that “infant-centric” factors—related to infant energetic needs—favor CF before six months to supplement breastfeeding. We apply these two frameworks in examining early CF among the Tsimane—a high-fertility, high-mortality, forager-horticulturalist population residing in the Bolivian Amazon. Data were collected from a mixed-longitudinal sample of 161 Tsimane mother-infant pairs from August 2012 – April 2013. Tsimane mothers generally reported introducing CF because of perceived infant needs. However, CF is introduced with continued intensive breastfeeding, and generally coupled with premastication. Risks of earlier CF relative to the minimum hazard (estimated at 5 births) were elevated for lower and higher parity mothers, but were significantly greater only after 9 births. Seventeen percent of mothers reported introducing CF because of low milk supply. Introducing CF because of low milk was most common from 0-3 months of age and among higher parity mothers, which may reflect physiological constraints. Maternal reproductive trade-offs and perceived infant needs may help explain the low prevalence of EBF to six months among other populations in which breastfeeding is not structurally or culturally constrained.

Growth references for Tsimane forager‐horticulturalists of the Bolivian Amazon

“…Pseudo-velocity curves suggest that between 6 and 24 months Tsimane height velocities for both boys and girls dip below WHO values. The timing of this divergence may coincide with the introduction of complementary foods, which may be a vector for disease and may affect nutritional availability (Veile et al, 2014; Martin, 2015). Divergence after 6 months is primarily in height, with Tsimane infants maintaining higher median BMIs and mean BMI velocities than infants in WHO references.…”

Salivary microbiomes of indigenous Tsimane mothers and infants are distinct despite frequent premastication

“…With increasing age and dental maturation, Tsimane infant oral microbiomes become more adult like, while the frequency of breastfeeding and premastication gradually decline (Martin, 2015; Veile et al, 2014). Younger children, therefore, may be protected by prebiotic and immunological constituents in breast milk and maternal saliva that selectively promote the growth of some commensals while inhibiting establishment of pathogens.…”

“…In a recent survey on the feeding practices of 132 Tsimane infants and young children aged 0–35 months (from here on “infants”), 84% of mothers reported premasticating foods for their infants at least once, and 54% reported premasticating foods the day prior (Martin, 2015). Fathers and siblings were observed sharing snacks with infants on occasion, but were not observed or systematically documented to premasticate.…”

Old friends and friendly fire: Pregnancy, hookworm infection, and anemia among tropical horticulturalists

“…The average Tsimane woman will give birth to nine children over her lifetime (Gurven, Costa, et al, 2016;Mcallister, Gurven, Kaplan, & Stieglitz, 2012). Tsimane women breastfeed on demand, with a mean weaning age of 19 months (Martin, Garcia, Kaplan, & Gurven, 2016;Veile, Martin, McAllister, & Gurven, 2014) and an average length of lactation amenorrhea of 13 months (Blackwell, unpublished analysis).…”