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 <i>ρ</i> = 0.384, <i>p</i> < 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.