Effect of a controlled dietary change on carbon and nitrogen stable isotope ratios of human hair

The carbon (¹³C/¹²C) and nitrogen (¹⁵N/¹⁴N) stable isotope ratios of human hair can be used for the interpretation of dietary habits and nutritional status in contemporary or past populations. Although the results of bulk or segmental isotope ratio analysis of human hair have been used for the reconstruction of an individual's diet for years, only limited data of controlled dietary changes on the carbon and nitrogen isotopic composition of human hair are available. Hair of four individuals, two males and two females, who participated in a dietary change experiment for 28 days was segmentally analysed for δ¹³C and δ¹⁵N. The dietary change included a change from C3 to C4 plant enriched diets and a simultaneous replacement of terrestrial animal products by marine products. This resulted in an increase in δ¹³C_diet of +8.5 to +9.9‰ and in δ¹⁵N_diet of +1.5 to +2.2‰. All subjects showed significant increases in δ¹³C_hair and δ¹⁵N_hair during the dietary change period, although no subject reached a new steady state for either carbon or nitrogen. The change in δ¹⁵N_hair was faster than the change in δ¹³C_hair for all individuals. The magnitude of change of the isotopic composition during the dietary change period could be attributed to the degree of physical activity of the individuals, with a higher physical activity resulting in a faster change. Copyright © 2009 John Wiley & Sons, Ltd.