Arsenic Species and Nitrogen Stable Isotope Ratios in the Japanese Diet—Dietary Markers of Seafood

Interest in seafood diet and health warrants a biomarker for seafood consumption. Nitrogen isotope ratio (15N/14N, expressed as δ15N (‰)) has been regarded as a biomarker for such a purpose. This study aims to elucidate the applicability of levels of arsenobetaine (AB), a non-toxic organic arsenic compound, in the diet as a marker of seafood abundance because of its known distribution in marine animals. The concentrations of AB and other arsenic species and δ15N in duplicate diet samples collected from 150 Japanese adults were analyzed for a possible relationship with the inclusion of seafood and seaweed in the diet samples. Information was collected from the menu reported from the duplicate diet donners, and a possible correlation between the levels of AB and δ15N was tested. As expected, median levels of AB and δ15N were more elevated in the duplicate diet that contained seafood (54.6 ng/g dry and 3.60‰) than that without seafood (<7 ng/g dry and 3.01‰). Additionally, there was a significant positive correlation between the two components (Spearman’s ρ = 0.384, p < 0.001). The distinct difference between the seafood-containing and non-containing diet suggested that the AB content of the diet is a more sensitive marker of seafood abundance than δ15N.