Arsenic metabolites in humans after ingestion of wakame seaweed

Abstract

Abstract. Seaweed contains large amounts of various arsenic compounds such as arsenosugars (AsSugs), but their relative toxicities have not yet been fully evaluated. A risk evaluation of dietary arsenic would be necessary. After developing an arsenic speciation analysis of wakame seaweed (Undaria pinnatifida), we conducted a wakame ingestion experiment using volunteers. Five volunteers ingested 300 g of commercial wakame after refraining from seafood for 5 days. Arsenic metabolites in the urine were monitored over a 5-day period after ingestion. Total arsenic concentration of the wakame seaweed was 34.3 ± 2.1 mg arsenic/kg (dry weight, n = 3). Two AsSugs, 3-[5′-deoxy-5′-(dimethyl-arsinoyl)-β-ribofuranosyloxy]-propylene glycol (AsSug328) and 3-[5′-deoxy-5′-(dimethyl-arsinoyl)-β-ribofuranosyl-oxy]-2-hydroxypropyl-2,3-dihydroxy-propyl phosphate (AsSug482) were detected, but arsenobetaine, dimethylarsinic acid (DMA), monomethylarsonic acid, and inorganic arsenics (iAs) were not detected. The major peak was AsSug328, which comprised 89% of the total arsenic. Approximately 30% of the total arsenic ingested was excreted in the urine during the 5-day observation. Five arsenic compounds were detected in the urine after ingestion, the major one being DMA, which comprised 58.1 ± 5.0% of the total urinary arsenic excreted over the 5 days. DMA was believed to be metabolized not from iAs but from AsSugs, and its biological half-time was approximately 13 h.

Effects of Dietary Intake of Arsenosugars and Other Organic Arsenic Species on Studies of Arsenic Methylation Efficiency in Humans

“…Ma and Le observed about 4.5 times increase of urinary DMA concentration from <20 μg/L in urine collected before ingestion to 90 μg/L in urine collected 26.5 h after the ingestion of 10 g yakinori seaweed. 64 Hata et al 86 observed significant increases in the excretion rate of DMA at 24 h after ingestion of wakame seaweed: 2.14 μg As/h vs 0.38 μg As/h. A total of 176.3 μg/L of arsenic (DMA proportion was over 50%) was excreted over 5 days after the ingestion of 300 g of wakame seaweed.…”

“…Hata et al observed significant increases in the excretion rate of DMA at 24 h after ingestion of wakame seaweed: 2.14 μg As/h vs 0.38 μg As/h. A total of 176.3 μg/L of arsenic (DMA proportion was over 50%) was excreted over 5 days after the ingestion of 300 g of wakame seaweed . A study on 16 volunteers in Korea with total arsenic 6.98 mg/person/day through seafood consumption found significant increases of total urinary arsenic with primary increase of DMA.…”

“…A total of 176.3 μg/L of arsenic (DMA proportion was over 50%) was excreted over 5 days after the ingestion of 300 g of wakame seaweed. 86 A study on 16 volunteers in Korea with total arsenic 6.98 mg/person/day through seafood consumption found significant increases of total urinary arsenic with primary increase of DMA. Average DMA% changed from 86% before seafood intake to 95% in urine collected 48 h after the end of six-day seafood intake.…”

The Health-Promoting Properties of Seaweeds: Clinical Evidence based on <i>Wakame</i> and <i>Kombu</i>

“…Wakame (soaked in 10 min) and kombu (soaked in 1 min) have an arsenic content of 34.7 and 51.2 µg/g, respectively 9 . The detection of arsenic metabolites in humans after ingesting wakame has been reported 10 .…”