Zinc is an essential trace element that plays an important role in many physiological functions. One of the key functions of zinc is its influence on the immune system. Zinc is required for the development and functioning of immune cells in the innate and the adaptive immune system. Zinc homeostasis is finely controlled within each cell and any deregulation results in impairment of normal functions. Consequences of impaired homeostasis can be observed in many disease models such as infections, allergies, autoimmune diseases, and cancers. Zinc deficiency negatively influences the hematopoiesis and compromises the immune response at multiple molecular, cellular, and systemic levels. This chapter summarizes how zinc is involved in the immune system and how altered zinc levels within cells influence the immune response.

Why do people take zinc?

Zinc has become a popular treatment for the common cold. Some studies have found that zinc lozenges may reduce the duration of cold, perhaps by a day or so, and may reduce the number of upper respiratory infections.

Zinc helps fight infection and heal wounds. However, if you already have enough zinc from your diet, it is not clear that getting even more — from supplements — has a benefit.

Topical zinc is used to treat diaper rash and skin irritations. Zinc has also been shown to help with ulcers, ADHD, acne, sickle cell anemia, and other conditions.

In addition, zinc has also been studied as a treatment for herpes, high cholesterol, rheumatoid arthritis, HIV, and more. However, the evidence of zinc’s benefit for these conditions is inconclusive.

Zinc may be part of an effective treatment for age-related macular degeneration, but more proof is needed.

Health care providers may recommend zinc supplements for people who have zinc deficiencies. Strict vegetarians, alcohol abusers, and people who have a poor diet are at higher risk for zinc deficiency. So are those with certain digestive problems, such as Crohn’s disease.

How much zinc should you take?

The recommended dietary allowance (RDA) includes the zinc you get from both the food you eat and any supplements you take.

Category	Recommended Dietary Allowance (RDA) of Zinc
CHILDREN
7 months to 3 years	3 mg/day
4-8 years	5 mg/day
9-13 years	8 mg/day
FEMALES
14-18 years	9 mg/day
19 years and up	8 mg/day
Pregnant	14-18 years: 12 mg/day 19 years and over: 11 mg/day
Breastfeeding	14-18 years: 13 mg/day 19 years and over: 12 mg/day
MALES
14 years and up	11 mg/day

The tolerable upper intake level (UL) of a supplement is the highest amount that most people can take safely. Never take more unless your health care provider says so. Keep in mind that this upper limit includes the zinc you get from foods and supplements.

Category (Children & Adults)	Tolerable Upper Intake Level (UL) of Zinc
0-6 months	4 mg/day
7-12 months	5 mg/day
1-3 years	7 mg/day
4-8 years	12 mg/day
9-13 years	23 mg/day
14-18 years	34 mg/day
19 years and up	40 mg/day

To avoid irritating the stomach, take zinc with food. For the common cold, zinc lozenges are typically taken every 2 to 3 hours within 48 hours of the start of symptoms. Then, take the zinc lozenges every 2 to 3 hours while awake until the symptoms go away. There are zinc supplements in pill and liquid form. 

What foods contain zinc?

Zinc is present in a wide variety of foods, but it is important to remember that phytates (the major storage form of phosphorous) can bind zinc and inhibit its absorption. Phytates are found in whole-grain bread, cereals, and legumes. This means that zinc contained in grains and plants is not as well absorbed as zinc found in seafood and meat.

Vegetarians should note that foods such as garlic and onions may increase the absorption of zinc from plant foods.

Examples of foods that are high in zinc and the amount of zinc they contain include:

• Oysters 3 ounces: 74mg
• Beef roast 3 ounces: 7mg
• Crab 3 ounces: 6.5mg
• Beef patty 3 ounces: 5.3mg
• Lobster 3 ounces: 3.4mg
• Baked beans ½ cup: 2.9mg
• Fortified breakfast cereal 1 serving: 2.8mg
• Pumpkin seeds 1 ounce: 2.2mg
• Yogurt 8 ounces: 1.7mg
• Cheese, swiss 1 ounce: 1.2mg
• Oatmeal 1 serving: 1.1mg
• Peas ½ cup: 0.5mg.

What are the signs of zinc deficiency?

Zinc deficiency may cause:

• Delayed sexual maturation
• Delayed wound healing
• Eye and skin lesions
• Growth delays
• Hair loss
• Hypogonadism in males or erectile dysfunction
• Impaired immune function
• Loss of appetite
• Taste abnormalities.

Zinc deficiency is difficult to measure in a laboratory because it is tightly contained throughout our body within proteins and nucleic acids. Sometimes zinc deficiency can be present even though laboratory results are normal.

Doctors need to consider a person’s risk factors (such as poor diet, presence of inflammatory bowel disease, alcoholism) together with symptoms of zinc deficiency before determining if zinc supplementation is needed.

Who is at risk of zinc deficiency?

Zinc deficiency in North America is uncommon. The following factors increase the risk of zinc deficiency:

• Age over 60 years
• Alcoholics
• Breastfeeding women
• Cancer
• Chronic diarrhea
• Chronic liver or kidney disease
• Diabetes
• Gastrointestinal surgery
• Infants older than 7 months who are exclusively breastfed
• Inflammatory bowel disorders, such as ulcerative colitis or Crohn’s disease
• Malabsorption syndrome
• Pregnant women with a marginal zinc status to begin with
• Short bowel syndrome
• Sickle cell disease
• Other chronic illnesses.

Vegetarians are at higher risk of zinc deficiency because they do not eat meat or seafood. They may require up to 50% more of the RDA to account for reduced zinc absorption because of the presence of phytates. The following increases the bioavailability of zinc from plant-based foods:

• Soaking beans, seeds, and grains in water for several hours before cooking
• Eating sprouted grains
• Eating leavened grain products, such as bread, rather than unleavened products such as crackers.

Can zinc cause side effects?

Yes. Zinc is a trace mineral which means we need a certain amount of it each day but taking high doses of zinc supplements can cause toxicity.

Side effects of zinc include nausea, vomiting, a loss of appetite, a bad taste, and a loss of smell.

High zinc can also inhibit the absorption of copper, which may result in copper deficiency and anemia.

Zinc supplements may also interact with medicines such as antibiotics, diuretics, and penicillamine.

You cannot over-consume zinc from zinc-containing foods.