Zinc
Zinc
is an essential mineral that is found in almost every cell of the body. It is necessary for proper growth and immune function. Oysters are well known for their zinc content. But, other animal foods are excellent sources of zinc, as well. You can also get zinc from plant-based foods. But, this zinc is not as well absorbed.
Functions
Zinc's functions include:
- Supporting normal growth and development during pregnancy, childhood, and adolescence
- Playing a role in tissue repair
- Helping the body use carbohydrate, protein, and fat
- Helping to maintain proper immune function, including promoting wound healing
- Serving as part of more than 70 enzymes that control body processes
- Maintaining a sense of taste and smell
- Maintaining normal vitamin A levels and usage
Recommended Intake
| Age Group |
Recommended Dietary Allowance
(mg/day) |
|
|---|---|---|
| Male | Female | |
| 0-6 months | 2 | 2 |
| 7-12 months | 3 | 3 |
| 1-3 years | 3 | 3 |
| 4- 8 years | 5 | 5 |
| 9-13 years | 8 | 8 |
| 14-18 years | 11 | 9 |
| 19+ years | 11 | 8 |
| Pregnancy: < 18 years | n/a | 12 |
| Pregnancy: 19-50 years | n/a | 11 |
| Lactation: < 18 years | n/a | 13 |
| Lactation: 31-50 years | n/a | 12 |
Zinc Deficiency
The human body is able to adapt to a short-term mild zinc deficiency by absorbing greater amounts from the foods you eat and excreting less. However, sustained inadequate zinc intake will affect bodily functions. While relatively rare in the US among most people, a zinc deficiency can have the following effects:
- Poor growth
- Hair loss
- Diarrhea
- Delayed sexual maturation
- Impotence
- Sterility
- Eye lesions
- Loss of appetite
- Reduced sense of taste and smell
- Skin lesions and inflammation
- Reduced resistance to infections
- Poor wound healing
- Mental lethargy
People who may be at risk for a zinc deficiency include:
- Pregnant or lactating women
- Elderly people
- Vegetarians
- People with sickle cell disease
- Alcoholics or others with chronic liver disease
- People with malnutrition from a variety of causes, including cancer and digestive diseases, that cause malabsorption and/or diarrhea, for example:
Zinc Toxicity
Zinc toxicity is rare in the US. However, people who take zinc supplements may reach toxic levels. Oversupplementation with zinc can cause a copper deficiency. Excess zinc may also cause the following:
- Diarrhea
- Cramps
- Nausea
- Vomiting
- Loss of appetite
- Suppressed immune function
- Impaired formation of red blood cells
- Reduced levels of HDL ("good") cholesterol
Major Food Sources
The Office of Dietary Supplements offers these examples of foods that are packed with zinc:
| Food | Serving size |
Zinc content
(mg) |
|---|---|---|
| Oysters | 6 medium | 76.7 |
| Beef shanks, cooked | 3 ounces | 8.9 |
| Crab, Alaska king, cooked | 3 ounces | 6.5 |
| Pork shoulder, cooked | 3 ounces | 4.2 |
| Breakfast cereal fortified with 25% of the Daily Value of zinc | ¾ cup | 3.8 |
| Chicken leg, roasted | 1 leg | 2.7 |
| Baked beans, canned | ½ cup | 1.7 |
| Cashews, dry roasted | 1 ounce | 1.6 |
| Yogurt, fruit, low-fat | 1 cup | 1.6 |
Health Implications
Sufficient levels of zinc are essential for your immune system to function properly. For example, zinc is required for the development and activity of T-lymphocytes. These are a type of white blood cells that help fight infection.
When people deficient in zinc are given zinc supplements, their immunity improves. These effects are most clearly seen among children in developing countries. For example, when these children are given zinc supplements, they have shorter courses of infectious diarrhea and are at a decreased risk of developing pneumonia.
Zinc lozenges, nasal sprays, and nasal gels may help to decrease the duration and severity of cold symptoms. They are believed to directly inhibit viruses in the nose and throat. However, this topic is still controversial, since the findings from scientific studies have been mixed. Moreover, nasal gels and sprays may cause permanent smell loss when used incorrectly.
Those studies that have found a positive effect suggest beginning zinc at the first sign of a cold. Different doses have been used in studies. For example, one trial found that 13 mg of zinc was helpful in shortening the length of a cold. This treatment should continue until symptoms subside, but not for longer than two weeks.
Zinc is also studied for its possible preventive effects. A recent review of zinc studies involving almost 400 children found that daily zinc supplements may reduce the risk of getting a cold.
If you want to take zinc on a daily basis or at the start of a cold, keep in mind the safe upper intake levels for this mineral:
| Age Group |
Tolerable Upper Intake Levels (ULs) for Zinc (mg/day) |
|
|---|---|---|
| Male | Female | |
| 0-6 months | 4 | 4 |
| 7-12 months | 5 | 5 |
| 1-3 years | 7 | 7 |
| 4- 8 years | 12 | 12 |
| 9-13 years | 23 | 23 |
| 14-18 years | 34 | 34 |
| 19+ years | 40 | 40 |
| Pregnancy: < 18 years | n/a | 34 |
| Pregnancy: 19-50 years | n/a | 40 |
| Lactation: < 18 years | n/a | 34 |
| Lactation: 31-50 years | n/a | 40 |
Minerals can compete with one another for absorption in the body. This is especially a concern when they are taken at high doses, such as those in supplements.
If you take calcium supplements but consume little or no zinc, you might need to take a multivitamin/mineral containing zinc. Most multivitamin/mineral pills contain 100% of the RDA for zinc.
Large doses of zinc can interfere with the body's absorption of copper and iron, other minerals that are essential. If you are taking a zinc supplement, talk to your doctor about your need for other supplements.
Resources:
American Dietetic Association
National Institutes of Health
Canadian Resources:
Dietitians of Canada
Health Canada
References:
The American Dietetic Association's Complete Food & Nutrition Guide. Chronimed Publishing; 1998.
Caruso TJ, Prober CG, Gwaltney JM Jr. Treatment of naturally acquired common colds with zinc: a structured review. Clin Infect Dis. 2007;45:569-574.
Dietary supplement fact sheet: zinc. National Institutes of Health website. Available at: http://ods.od.nih.gov/FactSheets/Zinc.asp. Accessed February 28, 2011.
Duyff RL. The American Dietetic Association's Complete Food & Nutrition Guide. 3rd ed. Hoboken, NJ: John Wiley and Sons, Inc; 2006.
Facts about dietary supplements. National Institutes of Health website. Available at: http://www.nih.gov/.
Garrison RH, Somer E. The Nutrition Desk Reference. New Canaan, CT: Keats Publishing; 1995.
Wardlaw G, Insel PM. Perspectives in Nutrition. 2nd ed. St. Louis, MO: Mosby; 1993.
Zinc. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/thisTopic.php?mar...ID=15topicID=114. Accessed January 2011.
2/4/2011 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance: Lassi Z, Haider B, Bhutta Z. Zinc supplementation for the prevention of pneumonia in children aged 2 months to 59 months. Cochrane Database Syst Rev. 2010;(12):CD005978.
Bhutta ZA, Black RE, Brown KH, et al. Prevention of diarrhea and pneumonia by zinc supplementation in children in developing countries: pooled analysis of randomized controlled trials. Zinc Investigators' Collaborative Group. J Pediatr. 1999;135(6):689-697.
Bhandari N, Bahl R, Taneja S, et al. Effect of routine zinc supplementation on pneumonia in children aged 6 months to 3 years: randomised controlled trial in an urban slum. BMJ. 2002;324(7350):1358.
Brooks WA, Santosham M, Naheed A, et al. Effect of weekly zinc supplements on incidence of pneumonia and diarrhoea in children younger than 2 years in an urban, low-income population in Bangladesh: randomised controlled trial. Lancet. 2005;366(9490):999-1004.
2/25/2011 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance: Sing M, Das R. Zinc for the common cold. Cochrane Database Syst Rev. 2011;(2):CD001364.
Last reviewed February 2011 by Brian Randall, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.