2
          
          
            ZnSO
            
              4
            
            
              
            
          
          +
          2
          
          
            H
            
              2
            
            
              
            
          
          O
          ⟶
          2
          
          Zn
          +
          
            O
            
              2
            
            
              
            
          
          +
          2
          
          
            H
            
              2
            
            
              
            
          
          
            SO
            
              4
            
            
              
            
          
        
      
    
    {\displaystyle {\ce {2ZnSO4 + 2H2O -> 2Zn + O2 + 2H2SO4}}}
  The sulfuric acid is regenerated and recycled to the leaching step.
With adequate zinc in the soil, the food plants that contain the most zinc are wheat (germ and bran) and various seeds, including sesame, poppy, alfalfa, celery, and mustard. Zinc is also found in beans, nuts, almonds, whole grains, pumpkin seeds, sunflower seeds, and blackcurrant.Other sources include fortified food and dietary supplements in various forms. A 1998 review concluded that zinc oxide, one of the most common supplements in the United States, and zinc carbonate are nearly insoluble and poorly absorbed in the body. This review cited studies that found lower plasma zinc concentrations in the subjects who consumed zinc oxide and zinc carbonate than in those who took zinc acetate and sulfate salts. For fortification, however, a 2003 review recommended cereals (containing zinc oxide) as a cheap, stable source that is as easily absorbed as the more expensive forms. A 2005 study found that various compounds of zinc, including oxide and sulfate, did not show statistically significant differences in absorption when added as fortificants to maize tortillas. Deficiency
Nearly two billion people in the developing world are deficient in zinc. Groups at risk include children in developing countries and elderly with chronic illnesses. In children, it causes an increase in infection and diarrhea and contributes to the death of about 800,000 children worldwide per year. The World Health Organization advocates zinc supplementation for severe malnutrition and diarrhea. Zinc supplements help prevent disease and reduce mortality, especially among children with low birth weight or stunted growth.