Racial differences in nitrogen content of nails among adolescents

Ectodermal derivatives provide a readily accessible means of chemically evaluating body protein composition. Therefore, it has been postulated that the analysis of nail nitrogen content may reflect recent nutritional status. Assessment of nail nitrogen content has been previously reported in a small group of neonates and school children. The present study was undertaken to determine if standards for nail nitrogen content could be established for adolescents which could then be used in the assessment of protein nutritional status. Nail clippings were obtained from 118 economically indigent urban black youth, 10 black and 39 white subjects from wealthy suburban communities in the New York area, and 10 poor white-Indian adolescents residing within a barrio in Lima, Peru. Nail samples were analyzed for protein content using the micro Kjeldahl technique. Mean nail nitrogen content for wealthy suburban and impoverished urban black youth was 136 and 137 mg N/g of nail, respectively. Values for poor Peruvian white-Indian and affluent suburban white adolescents were 142 and 141 mg N/g of nail, respectively. The differences between ethnic groups were significant using t test analysis at a P value of less than 0.001. No differences, however, were found between either wealthy and poor of the same racial background or when the data were analyzed by gender. These results suggest that differences in nail nitrogen content are at least in part a reflection of ethnicity. These racial differences must be considered in assessing nutritional status by nail nitrogen analysis.