Stable carbon and nitrogen isotope analysis of archaeological human hair: Reconstructing diet and health of ancient individuals

Stable isotope analysis is a powerful tool for reconstructing the diet and health of ancient individuals. The carbon and nitrogen stable isotope compositions of human tissues reflect those of the foodstuffs consumed and can be altered by physio-pathological stressors. The delta C-13 and delta N-15 values can be measured in the protein as a whole or in the amino acids constituting the protein by using a bulk or compound-specific isotope technique, respectively. Human scalp hair is considered an ideal tissue in stable isotope studies because it is resistant to degradation, is predominantly composed of proteins (keratins), grows fast and at a 'known' rate (circa 1 cm/month when in anagen phase), and it does not remodel after deposition. The isotope signal is recorded sequentially as the tissue grows and remains unaltered through time, with the most recent information found at the hair root. The sampling procedure is minimally invasive and therefore comparative studies on living individuals can be performed. Stable isotope analysis of sequential segments of scalp hair is a means of achieving a highly detailed and temporally resolved reconstruction of an individual's life. Dietary intake and health status of individuals can be reconstructed on a fortnightly basis when 0.5-cm-long hair segments are incrementally analysed.