Journal Article

Amino acid stable carbon isotopes in nail keratin illuminate breastfeeding and weaning practices of mother – infant dyads

Waters-Rist, Andrea L., Longstaffe, Fred J., Salahuddin, Hana

2025

Overview

Compound-specific stable carbon isotope analysis of amino acids (CSIA-AA) is widely used in ecological studies to analyze food-webs and is gaining use in archaeology for investigating past diets. However, its use in reconstructing breastfeeding and weaning practices is not fully understood. This study evaluates the efficacy of stable carbon isotope analysis of amino acids in early life diet reconstruction by analyzing keratin from fingernail samples of three mother-infant pairs during late gestation and early postpartum periods. Our results show that stable carbon isotope ratios ( δ 13 C) of glycine, and to a lesser extent glutamate, effectively trace the onset of exclusive breastfeeding and the end of weaning in infants. We propose that glycine’s ‘conditionally essential’ metabolic pathway during infancy allows it to reflect maternal glycine δ 13 C, indicating breastmilk consumption. Subtle changes in glutamate δ 13 C likely result from its ‘non-essential’ status. Additionally, δ 13 C values of glycine and glutamate indicate maternal physiological and pathological stress due to catabolic effects such as gluconeogenesis. These findings have significant implications for ecological and archaeological research using CSIA-AA for dietary reconstructions. They highlight the need to understand how metabolic pathways affecting δ 13 C of amino acids may change over an individual’s lifespan or be altered due to various forms of stress.

• Publisher: Springer Vienna,Springer Nature B.V,Springer
• Subject: Adult / Amino acids / Amino Acids - analysis / Amino Acids - metabolism / Analytical Chemistry / Archaeology / Biochemical Engineering / biochemical pathways / Biochemistry / Biomedical and Life Sciences / Breast Feeding / breast milk / Breastfeeding / Breastfeeding & lactation / Carbon / Carbon 13 / Carbon isotopes / Carbon Isotopes - analysis / Diet / Ecological effects / Female / Fingernail / Food chains / Food webs / Gluconeogenesis / glutamic acid / Glutamic Acid - metabolism / Glycine / Glycine - metabolism / Humans / infancy / Infant / Infant, Newborn / Infants / Isotope analysis / Isotope ratios / Isotopes / Keratin / Keratins - chemistry / Keratins - metabolism / Life Sciences / Life span / longevity / Metabolic pathways / Metabolism / Milk, Human - chemistry / Mother-offspring interactions / Nails - chemistry / Nails - metabolism / Neurobiology / Original / Original Article / Physiological effects / Pregnancy / Proteomics / stable isotopes / Weaning