Zinc

Animals, plants, and microbes all have enzymes which require zinc. There are more than 200 enzymes which need this element to function. They regulate growth, development, digestion, fertility, and the immune system.

Zinc in diets

The average adult takes in up to 40 mg of zinc per day, depending on their liking for red meats, which have some of the highest concentrations of zinc. The minimum intake needed to avoid zinc-deficiency symptoms is 2 mg per day. However, as only around 30% of ingested zinc is absorbed, the total intake has to be around 7 mg. Strict vegetarians get their zinc from sunflower or pumpkin seeds, brewer's yeast, maple syrup and bran. 

John Emsley explores zinc.