13Carbon and 15nitrogen isotopes in autopsy liver tissue samples from Greenlandic Inuit and Danes: consumption of marine versus terrestrial food

Abstract

The content of (13)C and (15)N isotopes is higher in marine than in terrestrial food. (13)C and (15)N in human tissue therefore reflects the relative proportions of marine and terrestrial food consumed by the individual. The objective of this study was to measure (13)C and (15)N in liver tissue from Greenlandic Inuit and Danes. Normal liver tissue was obtained at autopsy in 1992-1994 from 60 Inuit with a median age of 61 years (range 25-83) and in 1986 from 15 ethnic Danes with a median age of 84 years (range 66-93). By sieving, liver tissue was separated in a 'cellular fraction' and a 'connective tissue fraction'. (13)C and (15)N in dry liver tissue was measured on a mass spectrometer. delta(13)C indicates the (13)C content relative to the IAEA-CH-6 reference standard. delta(15)N indicates (15)N content relative to the atmospheric nitrogen reference standard. Inuit: median delta(13)C was -21.2 per thousand in cellular and -20.0 per thousand in connective tissue fractions (P=0.001). Median delta(15)N was 10.6 per thousand in both cellular and connective tissue fractions. Body mass index was negatively correlated with delta(13)C in the connective tissue fraction (r(s)=-0.42, P=0.057). Danes: median delta(13)C was -27.0 per thousand in cellular and -24.3 per thousand in connective tissue fractions (P=0.11). Median delta(15)N was 9.5 per thousand in cellular and 8.9 per thousand in connective tissue fractions (P=0.5). Inuit had higher delta(13)C than Danes in both cellular and connective tissue fractions (P<0.001) as well as higher delta(15)N in the cellular fraction (P=0.01). Inuit showed considerable variation in the ratio between marine and terrestrial food consumption, reflecting a vanishing hunter culture where elderly Inuit still adhere to the traditional hunters food with a high content of marine food, whereas the younger urbanized Inuit population consume food with a lower content of marine food and a higher content of terrestrial food. Danes consumed food of almost exclusively terrestrial origin. The present (13)C and (15)N analyses are in accordance with the dietary patterns obtained by dietary surveys.