The bioavailability of iron, lead and cadmium via gastrointestinal absorption: a review.

The primary route of entry of essential metals and most pollutant metals into the body is by gastrointestinal absorption. Although intraluminal factors influence the bioavailability of metals, the major control level of absorption probably resides in the intestinal mucosal cell. Interrelationships between various metals may effect their bioavailability at both the luminal and mucosal levels. It has also been shown that the nutritional status may have a profound influence on the absorption of some metals; iron, calcium, and protein deficiency may enhance the absorption of several pollutant metals, although this is apparently not simply an increased gut permeability to all heavy metals. Valid speculations regarding the absorption of pollutant metals is difficult since, even after several decades of intensive study, the precise mechanisms of controlling the absorption of iron and other trace metals are unknown.