Get Acquainted With Your Nutrients - Zinc

Zinc is a very important mineral and is found in almost every cell in the body. It exists as a constituent of several enzymes and also in hormone insulin. Zinc is crucial for normal development and function of immune system.

The body of an adult may contain about 2–3 grams of zinc and about 1% of it is replaced daily (1). Zinc is also present in skin, bone and prostate. Zinc is present in blood and is found in higher concentration in red blood cells than in plasma.

What does zinc do in the body?

Zinc is an essential mineral that is critical to a large number of structural proteins, enzymatic processes, and transcription factors. Zinc deficiency may cause a wide range of clinical symptoms.  Zinc plays a role in the biochemical reactions that regulate protein and nucleic acid synthesis and turnover. Zinc is important for preservation of ribosomal tertiary structure. It is a part of over 300 catalytic enzymes in the body (2).

Zinc is necessary for

• A healthy immune system
• For proper wound healing
• To maintain sense of taste and smell
• For DNA synthesis
• Normal growth and development
• Heme production
• Mineralization of bone (3)

Zinc also exhibits antioxidant activity and helps in protecting cells from damaging effects of free radicals (5)

How much zinc do we need per day?

The Adequate intake (AI) for zinc varies depending on age, sex and physiological status. Adults need 11mg (men) and 8 mg (women) per day. A pregnant lady needs 11 mg zinc per day and a lactating woman 12 mg a day (2).

Sources of zinc

Zinc is found in a wide variety of foods. Oysters are richest sources of zinc. Herring is also a rich source of zinc. Red meat and poultry are good sources of zinc. Beans, nuts, seafood, whole grains, fortified breakfast cereals and dairy products also provide dietary zinc (1, 2, 3).

Zinc absorption

Most of the dietary zinc absorption takes place in the small intestine (4). Zinc absorption depends on protein digestion. Zinc binds strongly to proteins near neutral Pᴴ. As protein is digested, zinc becomes available for transport through intestinal cells. Diets rich in protein need to be digested for the zinc to become available for absorption.

Zinc absorption is better from foods containing animal proteins than plant proteins. For example, cereals contain phytates which bind zinc and make it unavailable for absorption. Phytates inhibit the absorption and utilization of zinc in the body (5). Phytates which are found in whole grain breads, cereals, legumes and other products can decrease zinc absorption.

Zinc deficiency

Zinc deficiency may occur due to several reasons such as

• Dietary zinc intake is not sufficient
• When zinc is poorly absorbed
• When there is increased loss of zinc from the body
• When requirement for zinc increases

Zinc deficiency affects the normal functioning of several organ systems. Severe zinc deficiency affects integumentary (skin, hair, nails and exocrine glands), gastrointestinal, central nervous system, immune, skeletal, and reproductive systems (5).

Common signs of zinc deficiency include

• Growth retardation
• Hair loss
• Diarrhea
• Loss of appetite
• Rough skin
• Immune system damage

There is also research evidence that weight loss, delayed healing of wounds, taste abnormalities, and mental lethargy also may be seen in cases of zinc deficiency (5).

References

1. Cabrera A. J. (2015) Zinc, aging and immunosenescence: An overview, Pathobiology of aging & age related diseases. Vol. 5.

   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4321209/

2. Huang, L., Drake, V.J. and Ho, E. (2015) Zinc, Advances in Nutrition. Vol. 6(2).

   https://academic.oup.com/advances/article/6/2/224/4616692

3. Wildman, R. (2009) The Nutritionist-Food, Nutrition, and Optimal Health, Second Edition; The Minerals of Our Body 233; Routledge, Taylor and Francis Group, New York and London.
4. Roohani, N., Hurrell, R., Kelishadi, R. and Schulin, R. (2013) Zinc and its importance for human health: An integrative review, Journal of research in medical sciences. Vol. 18(2).
   

   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3724376/

5. Tuerk, M.J.. and Nasim, F. (2009) Zinc deficiency, Current Opinion in Gastroenterology. Vol.25 (2).

   https://journals.lww.com/co-gastroenterology/Fulltext/2009/03000/Zinc_deficiency.9.aspx#pdf-link