image: This is a traditional Shuar home. view more
Credit: PNAS
A study examines trade-offs between immunity and growth in Amazonian forager-horticulturalist children. Humans allocate energy expenditures in the form of calories to various metabolic tasks at different times, with trade-offs occurring as some tasks, such as immune function, receive increased energy and other tasks, such as growth, receive decreased energy. Samuel Urlacher and colleagues measured growth, subcutaneous body fat, and immune biomarkers in 261 children, 4-11 years of age, who are members of the Amazonian Shuar indigenous group. The study participants are forager-horticulturalists who consume a diet with low nutrient density and experience high rates of parasitic and infectious disease. The authors found that children expressing mild acute inflammation displayed a 49% reduction in concurrent growth. Various immune biomarkers reflecting different branches of immune function were associated with impacts on growth that lasted from 1 week to more than 1 year. The children with the highest body fat, however, exhibited no reduction in growth during periods of inflammation, suggesting that adipose tissue served to meet the energy shortfalls associated with immune function. According to the authors, the trade-off between growth and immune function suggests that immune energetics likely shapes patterns of human life history and may have contributed to the development of an extended childhood in human evolution.
Article #17-17522: "Tradeoffs between immune function and childhood growth among Amazonian forager-horticulturalists," by Samuel Urlacher et al.
MEDIA CONTACT: Samuel S. Urlacher, Hunter College, New York, NY; tel: 406-860-0090; e-mail: <samuel.urlacher@hunter.cuny.edu>
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