More than 50 years ago, in 1934, zinc essentiality was first suggested. Not until the early 1960s, however, was it known that low intake or low body stores of zinc can cause deficiency symptoms. In recent years, since the discovery that this mineral is becoming less available in our soil and thus in our food chain, zinc has been given more attention, and increased research has produced much new information. We now know that zinc is needed in probably more than 100 enzymes and is probably involved in more body functions than any other mineral. It is important in normal growth and development, the maintenance of body tissues, sexual function, the immune system, and detoxification of chemicals and metabolic irritants. Carbohydrate metabolism is influenced by zinc, and zinc is needed in the synthesis of DNA, which aids our body's healing process. Zinc is often helpful in reducing healing time after surgery or burns, in many male prostate problems, in skin diseases, and in many other difficulties.

Zinc is found in the body in small amounts, only about 2-2.5 grams total. Of the trace minerals, it is second in concentration to iron, with 33 ppm to iron's 60 ppm. (Although fluoride is found at 37 ppm in the average human body, it is still questionable whether it is essential. This 37 ppm is also a result of the use of fluoridated water, vitamins, and stannous fluoride toothpaste.) Though zinc is the twenty-fifth most abundant element in the earth's crust, measuring about 0.01 percent, it is water soluble both in the soil and in food. Rains can wash zinc (as well as iodine, sulfur, and selenium) from our farming soils, as can modern agricultural techniques. When we cook food, much of the zinc may go into the water, as do other minerals and vitamins, so the cooking liquids, especially from vegetables, should be consumed as well. More importantly, when foods are processed, as in the refining of grains, much of the zinc is lost, along with manganese, chromium, molybdenum, and B vitamins. Usually, only iron and sometimes vitamins B1 and B2 are added back in "enriched" foods (and this iron isn't even in the easily usable form). Adding zinc, manganese, chromium, and more B vitamins such as B6, would be much better and help us avoid common deficiencies.

Zinc absorption may vary from about 20-40 percent of ingested zinc, depending mainly on body needs and stomach acid concentrations. Like iron, zinc from animal foods where it is bound with proteins has been shown to be better absorbed. When bound with the phytates or oxalates found in grains and vegetables, less zinc is absorbed. Calcium, phosphorus, copper, iron, lead, and cadmium all compete with zinc for absoprtion. Milk and eggs reduce zinc absorption. Fiber foods, bran, and phytates, found mainly in the outer covering of grains, may also inhibit zinc absorption. Phytic acid may combine with the zinc in the upper intestine before this mineral can be absorbed.

The zinc-cadmium relationship is interesting. Cadmium is considered a potentially toxic heavy metal. When it contaminates our food, it is found in the center of grain; zinc is found mainly in the grain covering. So eating whole grains, which have a higher amount of zinc than of cadmium, will reduce any possible absorption of cadmium. With refining of grains into flour, the zinc-cadmium ratio is decreased, and cadmium is more likely to be absorbed and cause problems.