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absorption of Cd is dependent on factors such as age, pH, diet and intestinal metallothionein (MT) production. The chemical forms of Cd such as Cd-MT in foods or inorganic Cd administered directly in foods or drinking water have also been considered in literature. The bioavailability or absorption of Cd as Cd-MT in foods has been shown in many reports to have decreased in relation to Cd administered directly as inorganic Cd in drinking water or foods. However, some other studies have reported
contrary findings. Although research evidence has indicated that the type or components of a diet may also influence the absorption or toxicity of Cd irrespective of the chemical form involved. Diets low in proteins, minerals and certain vitamins have been reported to increase Cd absorption and toxicity. Conversely, diets rich in fibres have the reverse effect. The lack of conclusive information on the availability of Cd in Cd-MT for intestinal uptake in relation to that of ionic Cd is noticeable, and as a result there is a great need for further studies in this area. Also, since humans are usually exposed to Cd-MT in foods and rarely to inorganic Cd, the toxicity of food-incorporated Cd deserves further investigation, in view of the observed differences in tissue accumulation from these forms of Cd.