Fish arsenic may influence human blood arsenic, selenium, and T4:T3 ratio

The effects of an arsenic-rich fish diet and selenium (Se) supplementation on blood arsenic (As), Se, and thyroid hormones were studied in 32 women divided into four equal groups. Groups 1 and 4 received 400 microg Se-methionine daily, group 2 received 400 microg selenite daily, and group 3 received placebo tablets for 15 wk. In addition, groups 1-3 increased their fish intake, eating at least three fish dinners weekly. Mean blood Se concentrations (initially 1.68 +/- 0.24 micromol/L) increased twofold in the Se-methionine groups (p < 0.0001) and by 32% in the selenite group (p < 0.01). Group means of blood As concentrations increased by 63% (p < 0.01), 50% (p < 0.01), 106% (p < 0.01), and 29% (p < 0.05) in the four groups, respectively. Analyzed As intake from duplicate portions of consumed fish correlated with final blood As concentrations (r = 0.85, p < 0.001, n = 32). In the group not receiving Se, there was a positive correlation between final blood As concentrations and plasma T4:T3 ratio (r = 0.80, p < 0.02, n = 8). Initially, blood As concentrations correlated negatively with both T3 and T4 in plasma, but this correlation disappeared upon Se supplementation. The results demonstrate that increased intake of fish may influence blood As concentrations and that circulating thyroid hormones may be influenced by Se-As interactions.