Anti-nutritive effects of dietary tin

Tin is usually present in foods at levels of less than 4 micrograms/g. Higher levels may be found in some processed foods due to the addition of tin-based preservatives and stabilizers or to corrosion and leaching of the metal from unlacquered cans or from tin foils used in packaging. Estimates of dietary intake range from about 0.2 to greater than 5 mg Sn/day. Diets including a high proportion of canned vegetables and fish could supply greater than 30 mg Sn/day. Although intakes from dietary sources are generally considered to be harmless, a variety of adverse effects of tin have been reported, including effects on serum and bone alkaline phosphatase, lactic dehydrogenase, heme oxygenase, and 5-aminolevulinic acid dehydratase. Perturbations in glutathione metabolism have been reported, as have adverse effects on metabolism of essential trace minerals such as copper, zinc, and iron. Specific effects on calcium content of bone, serum, and kidney have also been described. Reported effects vary with the chemical form, dose of tin, and route and frequency of administration. Effects of tin in animal systems and on essential trace mineral absorption and excretion in human volunteers are reviewed. A summary of recent investigations on dietary tin-copper interactions and effects of tin on rat hepatocellular antioxidant protection are also presented.