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Am J Hum Biol. 2015 Nov-Dec;27(6):807-15. doi: 10.1002/ajhb.22729. Epub 2015 May 6.

Breastfeeding over two years is associated with longer birth intervals, but not measures of growth or health, among children in Kilimanjaro, TZ.

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Department of Biology and Women's, Gender, and Sexuality Studies Program, Boston University, Boston, Massachusetts, 02215.
Department of Anthropology, University of Auckland, Auckland, 1142, New Zealand.
Department of Anthropology, Binghamton University, SUNY, Binghamton, New York, 13902.
Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138.



Breastfeeding has been associated with numerous health and well-being benefits for both children and their mothers, including prolonging the birth interval to the subsequent sibling. The clearest associations between breastfeeding and health outcomes, per se, reflect exclusive breastfeeding in the first months of postnatal life and are most evident during infancy. Fewer studies explore the consequences of breastfeeding for multiple years. In this article, we ask whether breastfeeding for more than 2 years is associated with discernible health and well-being benefits to children.


Data were collected from 315 children, aged 2 to 7, and their caretakers residing in Kilimanjaro, Tanzania. Basic demographic and health information was solicited, and anthropometric and blood markers of health were evaluated.


Our results indicate a strong positive relationship between breastfeeding for 2 or more years and interbirth interval, but little evidence for a relationship between prolonged breastfeeding and several indicators of child growth and health.


We suggest that these relationships may support the recently rekindled birth spacing hypothesis, positing selection for longer interbirth intervals, rather than, or in addition to, more direct health benefits associated with breastfeeding for 2 or more years. Our results may indicate attenuating health benefits associated with longer breastfeeding.

[Indexed for MEDLINE]

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