Understanding Zinc and Its Functions

Zinc is a trace mineral: the body needs only a few milligrams a day, but it is found in cells throughout the body and takes part in a remarkable number of processes. Because the body has no dedicated store of zinc, a regular intake from food is important.

What zinc does

• Immune function: zinc helps the immune system fight off bacteria and viruses.
• Protein and DNA: the body needs zinc to make proteins and DNA, the genetic material in all cells.
• Growth and development: it is needed during pregnancy, infancy, childhood and adolescence.
• Wound healing: zinc helps wounds heal.
• Taste and smell: zinc is important for proper sense of taste.

How much you need

Recommended daily amounts from the NIH Office of Dietary Supplements:

• Men 19 and over: 11 mg
• Women 19 and over: 8 mg
• Pregnancy: 11 mg
• Breastfeeding: 12 mg

Food sources

• Oysters, which contain more zinc per serving than any other food
• Beef, pork and poultry
• Crab, lobster and other seafood
• Fortified breakfast cereals
• Beans, nuts and whole grains
• Dairy products and eggs

Zinc from plant foods is less well absorbed, because compounds called phytates in whole grains and legumes bind it. Soaking beans and choosing leavened bread can improve absorption.

Who may not get enough

Most people in the United States get enough zinc from food. Groups at greater risk of low intake include:

• people who have had gastrointestinal surgery or have digestive disorders such as Crohn’s disease or ulcerative colitis;
• vegetarians and vegans;
• pregnant and breastfeeding women;
• older infants who are exclusively breastfed;
• people with alcohol use disorder.

Signs of deficiency

Zinc deficiency can cause loss of taste and smell, poor appetite, slow wound healing, hair loss, diarrhea and more frequent infections. In children it slows growth. These symptoms have many other causes, so see a doctor rather than self-diagnosing.

Zinc and the common cold

Some studies suggest that zinc lozenges or syrup, started within a day of the first symptoms, may shorten a cold slightly. Results vary with the dose and form, and more research is needed. Zinc nasal sprays and gels have been linked to loss of the sense of smell, in some cases permanent, and should be avoided.

Supplements

Zinc is included in most multivitamin and mineral products, including our Daily Multivitamin, and is sold alone as zinc gluconate, zinc sulfate, zinc citrate and other forms. Check the label for the amount of elemental zinc.

Upper limit and side effects

The upper limit for adults is 40 mg a day from food and supplements combined. Too much zinc can cause nausea, vomiting, loss of appetite, stomach cramps, diarrhea and headaches. Taken over a long period, high doses can lower copper levels, reduce immunity and lower levels of HDL (“good”) cholesterol.

Interactions

• Antibiotics: zinc can reduce the absorption of quinolone and tetracycline antibiotics. Separate doses as your pharmacist advises.
• Penicillamine: zinc can reduce its absorption.
• Thiazide diuretics: increase the amount of zinc lost in urine.

Getting the balance right

Zinc illustrates a general rule for minerals: the gap between the amount you need and the amount that causes problems is not large. For most people, food plus a standard multivitamin is ample. High-dose zinc should be used only for a limited time or on medical advice.

The bottom line

Zinc supports immunity, healing and growth, and most balanced diets supply enough. Keep total intake below 40 mg a day unless your doctor says otherwise. See mineral-containing products in our vitamins and nutrition department.

Sources

1. NIH Office of Dietary Supplements. Zinc.
2. MedlinePlus. Minerals.
3. NHS. Vitamins and minerals.