Zinc, an essential trace mineral, is necessary for a myriad of life-sustaining body functions, including cell division, the synthesis of protein, the catalytic activity of enzymes, proper immune function and the healing of wounds. It also supports growth and development in children and teenagers and is essential for your sense of taste and smell. According to New Jersey Medical School, roughly 15 percent of the United States population take supplementary zinc. However, excessive dosages of zinc can cause serious health problems; consult your physician before taking supplementary zinc.
Dietary and Supplementary Zinc
Zinc is found in meat, poultry, seafood and dairy products; good vegetarian sources include legumes, nuts and whole grains. The Office of Dietary Supplements lists the recommended dietary allowance for men as 11 mg per day; women should get 8 mg. Doctors prescribe supplemental zinc to treat a variety of conditions, including macular degeneration, ulcers and herpes simplex. Zinc may help reduce the duration of cold symptoms, especially when taken within 24 hours of onset. Supplemental zinc is available in the form of zinc gluconate, zinc sulfate, zinc acetate and zinc picolinate. The ODS reports that the amount of actual -- or elemental -- zinc varies according to each formulation; check the supplement facts panel on the container for the exact proportion of elemental zinc. Zinc nasal sprays, linked with loss of sense of smell, were withdrawn from the market after the FDA issued a consumer warning in 2009.
Acute Zinc Toxicity
Acute zinc toxicity, a onetime overdosage of zinc, can be caused when you eat or drink food or beverages that have been contaminated with zinc due to storage in galvanized containers. Symptoms are abdominal pain, severe nausea and vomiting, and diarrhea. The American Cancer Society reports at least one case on record of zinc toxicity causing kidney failure and death. Linus Pauling Institute at Oregon State College notes that doses of zinc between 225 and 450 mg can cause vomiting; amounts as low as 50 mg can cause gastrointestinal distress.
Chronic Excessive Zinc
Dosages as low as 50 mg of zinc a day can interfere with your body's absorption of copper, putting you at risk for copper deficiency and anemia. Symptoms include lethargy, nausea, a metallic taste, blood in the urine, and reduced levels of beneficial HDL cholesterol. According to New Jersey Medical School, taking more than 100 mg of zinc a day may promote more aggressive tumors in cases where prostate cancer has developed. However, no relationship was found between dietary zinc and prostate cancer. Taking over 300 mg a day of zinc decreases white blood cells and impairs immune function. The National Institutes of Health advises an upper limit of 40 mg of zinc a day from food and supplements combined.
Research
In a scientific analysis published in 2007 in the "Journal of Urology," researchers found that patients taking 80 mg of zinc for six years as part of an age-related eye disease study experienced significantly more hospital admissions for genitourinary infections than the control group. Benign prostatic hyperplasia, urinary tract infections and kidney failure were among the most common disorders. The team concluded that high-dose zinc supplementation has negative effects on urinary physiology.
References
- Office of Dietary Supplements: Zinc
- University of Maryland Medical Center: Zinc
- Linus Pauling Institute at Oregon State University; Micronutrients: Zinc; Jane Higdon, PhD.; December 2003
- "Journal of Urology"; High Dose Zinc Increases Hospital Admissions Due to Genitourinary Complications; A.R. Johnson et al.; February 2007
- New Jersey School of Medicine: Too Much Zinc Could Be Harmful
- The American Cancer Society: Zinc
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