Effects of vitamin D on the absorption and retention of lead

Abstract

A relationship between lead retention and vitamin D has been recognized for many years, but the reasons for this association remained unknown. In rats, the manipulation of dietary vitamin D content had no significant effect on the absorption of lead from isolated gut loops and parenteral vitamin D stimulation did not affect lead absorption in rachitic animals. In contrast, dietary vitamin D deficiency and repletion resulted in increased absorption in intact animals due to prolonged gastrointestinal transit time. Both dietary vitamin D deficiency and repletion were associated with decreased body retention of radiolead given intravenously. Further, single doses of parenteral vitamin D administered to animals previously given tracer radiolead resulted in a dose-related enhancement of lead excretion and changes in tissue lead content.

Chronic Ayurvedic medicine use associated with major and fatal congenital abnormalities

“…Exposure to lead and reduced iron status result in greater impairment than the lead-associated impairment in heme biosynthesis alone (Kwong et al 2004;Mahaffey-Six and Goyer 1973). Such findings were confirmed in humans, as well as experimental animals (Barton et al, 1978;Mahaffey 1983). …”

“…Iron deficiency is associated with increases in absorption and deposition of lead (Barton et al 1978). Several cross-sectional studies in children showed an inverse relationship between iron status and blood lead (Brad man et al 2003;Choi and Kim 2003;Hammad et al 1996).…”

Seasonal changes in lead absorption in laboratory rats.

“…This result suggests that lead absorption among children could also be increased in the summer, but this latter phenomenon is not necessarily a result of the same mechanisms operant in laboratory rats. The seasonal maxima in blood concentrations of vitamin D metabolites may not stimulate lead absorption, but vitamin D could precipitate or exacerbate plumbism by accelerating the release of lead from storage sites in bone (17,32). Although body iron repletion, dietary iron content, and intestinal iron transport mechanism(s) are significant regulator(s) of lead absorption and important epidemiologic factors in childhood plumbism, the effect of season on iron absorption and metabolism is virtually unstudied.…”

Seasonal Changes in Lead Absorption in Laboratory Rats

“…Blood vitamin D was not quantified in our rats, but their lighting exposure alone appears to be an inadequate explanation for seasonal variation in vitamin D metabolites. 1,25-dihydroxyvitamin D administration increased the retention of orally administered radiolead in mice and rats, and the absorption of radiolead in chicks (17,46,47); in rats, however, this was an effect of prolonged gastrointestinal transit time rather than stimulation of the mucosal phase of radiolead absorption (17). Further, the active transport of calcium (48), but not lead (49), occurs with circadian rhythmicity in rat intestine tn vitro.…”

“…This result suggests that lead absorption among children could also be increased in the summer, but this latter phenomenon is not necessarily a result of the same mechanisms operant in laboratory rats. The seasonal maxima in blood concentrations of vitamin D metabolites may not stimulate lead absorption, but vitamin D could precipitate or exacerbate plumbism by accelerating the release of lead from storage sites in bone (17,32). Although body iron repletion, dietary iron content, and intestinal iron transport mechanism(s) are significant regulator(s) of lead absorption and important epidemiologic factors in childhood plumbism, the effect of season on iron absorption and metabolism is virwtually unstudied.…”