It is a well established fact that Zinc is an important regulator in the proper functioning of the immune system - the organized structure that protects the body by producing immune response.
Zinc ensures the proper action of leucocytes, neutrophils, monocytes, and lymphocytes. Leucocytes are large colorless (contains no hemoglobin) white blood cells. Neutrophils are the chief phagocytes in white blood cells; they eat bacteria and debris. Monocytes are large white blood cells that are formed in the bone marrow, enters the blood and migrates into connective tissue where it differentiates into macrophages - they also destroy foreign antigens such as bacterias and viruses. Lymphocytes are white blood cells produced in the lymphoid tissue. B lymphocytes produce antibodies while T lymphocytes attack and destroy antigens directly.
A recent study conducted by Dr. Veverka and his colleagues shows that subjects who took zinc supplements experienced lower risks of upper respiratory infections than those in the placebo group. The seven (7) month randomized double-blind placebo investigation involved 40 cadets. The results of the trial were published in the 2009 issue of Complementary Therapies in Clinical Practice.Their findings confirm what other researchers have documented. In 1998, Sazawal and colleagues reported that zinc supplementation reduced the severity and frequency of respiratory infections in children. The subjects involved 609 children aged 6-35 months old. The control group received 10 mg of elemental zinc for 120 days while the other group received a placebo. The researchers found that dietary zinc supplementation significantly reduced the incidence and morbidity of respiratory illness in pre-school children.
In 2006, Aggarwal and others reviewed 17 previous studies on zinc's efficacy in reducing the incidence, and severity of respiratory infections. They also found that those who received zinc supplemenation experienced fewer episodes of respiratory tract infections than those who received placebos.
The Nature and Biological Functions of Zinc
Zinc is a trace element required as a co-factor in more than 100 enzymes. Almost all cells contain zinc with the highest amounts in bone and muscle tissues. Zinc:
- bolsters the work of many proteins including metalloenzymes - enzymes that contain one or more minerals as part of their structures
- stabilizes cell membranes, helping to strengthen their defense against free radical attacks
- participates in the storage, and release of insulin in the pancreas
- interacts with platelets in blood clotting
- affects thyroid hormone function
- influences behaviour and learning performance
- is required in the activation of vitamin A and the retinol-binding protein that transports vitamin A
- is essential to normal taste perception
- is vital in wound healing and immune function
Zinc deficiency is not prevalent in developed countries. However, Middle Eastern countries (Egypt, Iran, and Turkey) have been reported to have zinc deficient diets due to their lower meat content. The typical diet contain legumes, unleavened breads, and other whole-grain, high-fiber (phytate) foods that prevents zinc absorption. Pregnant women, young children, the elderly, the poor, and those with compromised immune systems who face increased risks of infections are the most vulnerable populations.
Minimum and Maximum Recommended Zinc Daily Allowances for Healthy Adult Men and Women
Males: 11 mg/day; Females: 8 mg/day; Maximum: 40 mg/day
Significant Dietary Sources: Meats, fish, poultry, seafood such as oysters, legumes and nuts.
References
Veverka DV et al. "Use of zinc supplements to reduce upper respiratory infections in United States Air Force Academy Cadets" Complimentary Therapies in Clinical Practice May 2009;15(2):91-95
Sazarwal S et al. "Zinc Supplementation Reduces the Incidence of Acute Lower Respiratory Infections in Infants and Preschool Children: A Double-Blind, Controlled Trial" Paedriatrics July 1998;102(1):1-5
Aggarwal R et al. "Role of Zinc Administration in Prevention of Childhood Diarrhea and Respiratory
Illness: A Meta-Analysis" Paediatrics June 2007; 119(6):1120-1130
Whitney EN & Rolfes SR "Zinc" Understanding Nutrition, Ninth Edition Wadsworth, CA, 2002 Chapter 13, pp:439-443
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