
Dietary
Mineral Status Key to Cadmium ToxicityBy Rosalie Marion
Bliss July 22, 2002A lack of dietary iron, zinc and
calcium results in unhealthy increases in cadmium uptake into the kidney and
liver, Agricultural Research Servicescientists report. Staple grains such as rice, wheat and maize differ greatly
in their levels of these three key minerals that counteract the absorption, or
bioavailability, of cadmium. The scientists examined test rats fed a rice-based diet with various
marginal levels and combinations of iron, zinc and calcium, along with cadmium
at levels that actually occur in foods. Rats fed adequate amounts of the same
mineral or minerals served as control groups. Rats fed only marginal iron or
calcium had a threefold higher retention of cadmium than controls. But rats fed
marginal levels of all three--zinc, iron and calcium-- retained a whopping
eight times more cadmium than rats fed adequate minerals. The research suggests that populations exposed to marginal mineral intakes
are at greater risk of absorbing increased amounts of cadmium than
well-nourished populations exposed to similar amounts of cadmium. The study
could have serious implications for people who eat subsistence rice diets too
low in zinc, iron or calcium. In areas of Japan and China where rice is grown on soils contaminated by
mining wastes, people have suffered adverse health effects from cadmium intake.
Yet people in other countries who consumed similar amounts of cadmium in foods
grown on more highly contaminated soils did not experience adverse effects from
cadmium intake; those foods contained adequate zinc, iron, and calcium to
retard cadmium absorption into the body. Previous studies only hinted at the importance of zinc, iron and calcium's
preventative effects on the absorption of cadmium. Those studies employed
unnaturally high quantities of the minerals and looked only at intestinal
absorption. The current study, which appears in July's Environmental Science
& Technology, was conducted by research chemist Philip G. Reeves
and research agronomist Rufus L. Chaney, both with ARS, the
U.S. Department of Agriculture's chief
scientific research agency. U.S. Department of Agriculture |