What is zinc and why is it important?
Zinc is an essential trace element needed by all forms of life. In the human body, over 300 enzymes require zinc for proper functioning. It is also estimated that 3000 of the over 10,000 proteins in our bodies contain zinc. Additionally, our bodies contain about 2-3g of this mineral. There are no specific storage sites known for zinc and so a regular supply in the diet is required. About 60% of our body's zinc is found in muscle, 30% in bone and about 5% in our skin. Particularly high concentrations of zinc are also found in the prostate gland.
What is the best way to increase our zinc intake?
The current Recommended Daily Allowance (RDA) for zinc is 15 milligrams per day. Short term doses of 40mg/day are often beneficial but taking large quantities of zinc (50 mg/day or more) over a period of weeks can interfere with copper bioavailability and can cause toxicity and can suppress the immune system.
Zinc is found in a wide variety of foods. Oysters contain more zinc per serving than any other food, but red meat and poultry provide the majority of zinc in the American diet. Other good food sources include beans, nuts, seeds, seafood, whole grains, fortified breakfast cereals, and dairy products. For vegetarians, remember that pumpkin seeds provide one of the most concentrated plant based food sources of zinc.
Who can benefit most from extra zinc?
Symptoms of zinc deficiency include but are not limited to acne, weight loss, chronic infections, slow wound healing, rough skin, impaired taste and smell, hair loss, mental lethargy and chronic diarrhea.
The following groups are most susceptible to zinc deficiency and should consider increasing their ingestion of zinc rich foods and/or adding a zinc supplement:
Infants and children
Pregnant and breast-feeding women
Patients receiving intravenous feedings
Malnourished and anorexia nervosa patients
Individuals with severe or persistent diarrhea
Individuals with malabsorption syndromes and inflammatory bowel disease
Chronic alcoholics
Older adults (65 years and older)
Strict vegetarians
What does the scientific research say about the benefits of zinc?
1. Colds and the immune system
A study was performed in 2000 in which 48 students were given either a 12.8 mg zinc lozenge or a placebo. Both groups received 50 lozenges and were asked to take one every 2-3 hours for the duration of their cold symptoms. The group receiving the zinc suffered from cold symptoms an average of 4.5 days while the placebo group was sick for an average of 8.1 days. Also, the zinc recipients coughed for only 3 days compared to the 6 days for the placebo patients. No other cold remedies were taken at the time of the study so the conclusion strongly suggests that zinc supplementation strengthens the immune response. Think of zinc next time you have a cold!
Recent research has also helped us to understand why zinc is so necessary to the immune system. Researchers in the department of cell biology and human anatomy at the University of California Davis School of Medicine, have found that deficiencies of zinc may reduce natural killer (NK) cell function. A reduction in NK cells leaves the immune system vulnerable and less able to clean up pathogens like bacteria, viruses and even cancer cells.
2. Wound Healing
Zinc is also necessary to maintain the health and integrity of epithelial cells that line the intestines. A study has shown that supplementation with adequate zinc at 12.5-50 mg/day enhanced intestinal wound healing. This is exciting information as inflammatory bowel disease, a serious intestinal disorder, causes intestinal lesions, which zinc has been found to help heal.
3. Prostate Health
A multi center hospital-based case-control study on prostate cancer was performed in Italy. Approximately 3000 prostate cancer patients were given varying amounts of zinc supplementation. The findings from this large study are that higher doses of zinc equate with a lower risk of prostate cancer. Another similar study correlated low concentrations of zinc in prostate tissue with the increased presence of prostate cancer. The number of studies connecting prostate health with zinc is growing daily. Just remember to always consider zinc when treating the male reproductive system.
Erika Correnti, ND
Kirkland, WA
References
Cortesi M, et al: Clinical assessment of the cancer diagnostic value of prostatic zinc: a comprehensive needle-biopsy study Prostate. Jun; 68(9): 994-1006, 2008.
Erickson KL, et al: Micronutrients and innate immunity. J Infect Dis Sep;182(Suppl)1:5S-10S, 2000.
Gallus S et al: Dietary zinc and prostate cancer risk: a case-control study from Italy. Eur Urol. Oct; 52(4):1052-6, 2007.
Hocke M et al: Oral zinc therapy in patients with supposed mild zinc deficiency—a critical review. Z Gastroenterol Jan;39(1):83-8, 2001.
Prasad: Duration of Symptoms and Plasma Cytokine Levels in Patients with the Common Cold Treated with Zinc Acetate: A Randomized, Double-blind, Placebo-controlled Trial Annals of Internal Medicine Aug; 133 (4): 245—252, 2000.
