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What is zinc?

Zinc is one of the most active minerals in the body as it influences the functioning of hundreds of different enzymes. Although often overshadowed in the popular press by the likes of iron and chromium, lately zinc has been thrust into the limelight. Zinc supplements have been purported to reduce the length and severity of the common cold, which will be discussed.

 

What foods provide zinc?

In living things, zinc is more associated with amino acids and proteins. Therefore, it is logical to presume that animal foods, with their higher protein content, would be better zinc sources than plant foods. This is true. The best sources of zinc include organ meats, other red meats, and seafood (especially oysters and mollusks). Poultry, pork, milk and milk products, whole grains (especially germ and bran), and leafy and root vegetables are also respectable contributors of zinc.

What are the levels of recommended intake for zinc?

The AI for zinc varies depending on age gender and condition. For instance, the AI for adult women and men is 8 and 11 mg while the AI for pregnant and lactating women is 11 and 12 mg daily.

 

What factors can influence zinc absorption?

Absorption of zinc from the digestive tract is not well understood. However, it does seem that many factors can influence how efficiently zinc is absorbed. For instance, zinc derived from meat boasts better absorption than zinc from plant sources. Zinc absorption from meat may actually be enhanced by certain amino acids, which would be present during simultaneous protein digestion. On the other hand, the efficiency of zinc absorption from plant foods seems to be lower which may in part be due to the presence of phytate, oxalates, and probably other substances (tannins) also found in many plants. Recommendations for dietary zinc takes into consideration the impact of various substances on zinc absorption.

 

What does zinc do in the body?

The distribution of zinc in the body may provide some indication as to its broad and extensive function. Zinc is found in all tissue of the body and is believed to be necessary for more than 200 different chemical reactions. Zinc largely functions as a necessary component of various enzymes, which would regulate all of those chemical reactions. In fact, the number of enzymes whose optimal function relies upon zinc is probably greater than the total number of enzymes that rely on all of the other trace elements combined. Zinc is involved with enzymes that affect body:

 

  • Antioxidant protection (super­oxide dismutase)

  • pH (carbonic anhydrase)

  • Alcohol metabolism (alcohol dehydrogenase)

  • Bone mineralization (alkaline phos­phatase)

  • Protein digestion (carboxypeptidases)

  • Protein and nucleic acid metabolism (polymerases)

  • Heme production

  • Immunity.

     

What happens if we get too little zinc?

Zinc deficiency results in aberrations stemming from a decreased activity of zinc-dependent enzymes. These signs include stunted growth in children, abnormal bone growth and/or mineralization, delayed sexual maturation, decreased immune capacity, and poor wound healing. Because of zinc’s widespread function throughout cells, many people feel that zinc supplementation is a necessity.

 

Can zinc become toxic?

Zinc toxicity would tend to happen only by supplementation. One of the biggest concerns with higher zinc intakes is its relationship to copper. It is possible to reduce copper intake and induce signs of copper deficiency by consuming as little as three to ten times the RDA for zinc over several months. Because of the inverse relationship between dietary zinc and copper absorption, the utilization of high zinc supplements is not recommended unless a physician has recognized a need. This is particularly true for people who use zinc supplements to treat the common cold. These supplements should not be continued beyond five to seven days.