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Zinc

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image 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
  • Maintaining a sense of taste and smell

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
  • Reduced resistance to infections
  • Poor wound healing
  • Mental lethargy
People who may be at risk for a zinc deficiency include:

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

Most of what we eat on a daily basis can give us the amount of zinc we need. Here are some common foods that have zinc:
Food Serving size Zinc content
(mg)
Oysters 6 medium 76.2
Beef , chuck or roast, cooked 3 ounces 8.7
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, broiler or fryer, cooked 3 ounces 2.4
Baked beans, canned ½ cup 1.7
Yogurt, fruit, low-fat 1 cup 1.6
Remember to read labels. If there is zinc in the food product, it will be listed with the amount.

Health Implications

Infections

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.

The Common Cold

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.
Some studies of taking zinc pills have found that the duration of cold symptoms to be shorter when zinc was taken, but each study had different doses, which can affect the outcomes. Age also plays a factor in whether or not zinc relieves cold symptoms. In a review of 17 trials, there was little effect on children and the duration of their cold symptoms.
Zinc is also studied for its possible preventive effects. A review of zinc studies involving almost 400 children found that daily zinc supplements may reduce the risk of getting a cold.
Some of the more common side effects included bad taste in the mouth, and nausea. 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

Absorption of Calcium, Iron, and Copper

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 Recommended Daily Allowance 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.

Pregnancy Nutrition Support and Prevention of Preterm Birth

Good nutrition is important during pregnancy for the mother and the baby. This includes eating plenty of fruits, vegetables and healthy proteins. Your doctor may recommend supplements like a zinc supplement if you are having a hard time with nutrition during pregnancy. Getting correct amounts of zinc may help prevent delivering a baby prematurely.

RESOURCES

American Dietetic Association http://www.eatright.org

National Institutes of Health http://www.nih.gov

CANADIAN RESOURCES

Dietitians of Canada http://www.dietitians.ca

Health Canada http://www.hc-sc.gc.ca/index%5Fe.html

References

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.

Copper deficiency. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what. Updated November 15, 2012. Accessed January 25, 2013.

Nutrition in pregnancy. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what. Updated January 23, 2013. Accessed January 25, 2013.

Zinc. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/healthLibrary. Updated September 10, 2012. Accessed January 25, 2013.

Zinc. National Institutes of Health Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/Zinc-QuickFacts/. Updated September 20, 2011. Accessed January 25, 2013.

Zinc content of selected foods per common measure. USDA National Nutrient Database for Standard Reference. Available at: http://www.nal.usda.gov/fnic/foodcomp/Data/SR20/nutrlist/sr20w309.pdf. Accessed January 25, 2013.

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.

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.

10/25/2012 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance: Mori R, Ota E, Middleton P, Tobe-Gai R, Mahomed K, Bhutta ZA. Zinc supplementation for improving pregnancy and infant outcome. Cochrane Database Syst Rev.2012 Jul 11;7:CD000230.

Revision Information

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

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