Amino Acid Composition of Human Hair

Samples of hair from five different female Caucasians were selected, while attempting to eliminate or minimize variables introduced by factors, suggested in previous literature, related to genetics, malnutrition, and cosmetic alteration, to analyze for 18 amino acids. The objective was to determine if human hair from such a similarly sampled group differs in composition from individual to individual. Significant differences were found for 9 of the 18 amino acids analyzed at the α = 0.01 level, however, the percent deviations for 16 of the amino acids were within ± 6%. Comparison of these samples of hair with pooled dark brown hair, from female Causasians, and purchased from a hair dealer, indicated a note-worthy difference only in the cystine content. Comparison of these data from human hair with that from 64's Merino wool indicates substantial differences between cystine, glycine, tyrosine, and phenylalanine. Statistically significant differences were suggested for other amino acids between Merino wool and human hair; however, the magnitude of the numerical differences, in these instances, was substantially lower than for the above mentioned four amino acids. Weathering effects in human hair were also explored, suggesting degradation to the amino acid residues of cystine, tyrosine, hysine, and histedine by the elements.