Zinc is an essential nutrient present naturally in some foods and sometimes also consumed as a dietary supplement. It plays a role in cellular metabolism, immune function, protein synthesis, wound healing, DNA synthesis and cell division. As a nutrient, it is required all through pregnancy to adolescence. A daily intake of zinc is required to maintain a steady state because the body has no specialized zinc storage system. The daily recommended allowance for zinc is 8 mg/ day in adult females and 11 mg/ day in adult males. Zinc deficiency is characterized by growth retardation, loss of appetite, and impaired immune function.
Zinc deficiency is common for crop plants and hence supplemented through fertilizers. Other ways by which the soil can become contaminated with zinc is through fossil fuel combustion, dumping of sludge and industrial waste. Although excess zinc in the body can cause toxicity, the occurrence is isolated and rare. Acute toxicity could be caused by zinc released from galvanized containers into food and beverages. The signs of toxicity include- abdominal pain, diarrhea, nausea, and vomiting. The major complication of long term consumption of zinc is copper deficiency.
Zinc limits
In drinking water, the permissible limit of zinc as per BIS (Bureau of Indian Standards) IS 10500:1991 is 15 mg/l, in the absence of alternate source and 5 mg/l is the requisite limit.
The limits for zinc in various food categories have been specified by FSSAI as follows:
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