Zinc is an essential trace mineral, so you get it through the foods you eat. Next to iron, zinc is the most common mineral in the body and is found in every cell. It has been used since ancient times to help heal wounds and plays an important role in the immune system, reproduction, growth, taste, vision, and smell, blood clotting, and proper insulin and thyroid function.

Zinc also has antioxidant properties, meaning it helps protect cells in the body from damage caused by free radicals. Free radicals may contribute to the aging process, as well as the development of a number of health problems, including heart disease and cancer. Antioxidants can neutralize free radicals and may reduce or even help prevent some of the damage they cause.

Your body doesn't need a large amount of zinc. The recommended daily allowance for adults is 8 - 11 mg. It’s common to have slightly low levels of zinc, but taking a multivitamin, plus eating a healthy diet, should give you all the zinc you need.

It's rare for people in industrialized countries to be seriously deficient in zinc. Low zinc levels are sometimes seen in the elderly, alcoholics, people with anorexia, and people on very restricted diets. People who have malabsorption syndromes, such as Crohn's disease or celiac disease, may also be deficient in zinc.

Symptoms of zinc deficiency include loss of appetite; poor growth; weight loss; lack of taste or smell; poor wound healing; skin problems such as acne, atopic dermatitis and psoriasis; hair loss; lack of menstrual period; night blindness; white spots on the fingernails; and depression.

Zinc reduces the amount of copper your body absorbs, and high doses of zinc can cause a copper deficiency. For that reason, many doctors recommend that you take 2 mg of copper along with a zinc supplement.

Acne

Some studies suggest that taking oral zinc supplements may help improve acne. However, most studies used a high dose of zinc that could have toxic effects, and not all studies found any benefit. There is some evidence that a topical form of zinc, used along with the topical antibiotic erythromycin, might be helpful.

Age-Related Macular Degeneration(AMD)

Doctors often recommend zinc to slow the progress of AMD, an eye disease that occurs when the part of the retina that is responsible for central vision starts to deteriorate. A major clinical trial, the Age Related Eye Disease Study (AREDS1), found that people who had macular degeneration could slow down the damage by taking zinc (80 mg), vitamin C (500 mg), vitamin E (400 mg), beta-carotene (15 mg), and copper (2 mg). If you have macular degeneration, ask your doctor whether these vitamins and minerals might help you. This is a very large amount of zinc and should only be used under a doctor's supervision.

A new study, AREDS2, is examining exactly what role zinc plays in macular degeneration.

Colds

Many people believe that taking zinc lozenges or using zinc nasal spray when they first show signs of a cold can reduce the duration and severity of symptoms. Not all studies agree, but most suggest that zinc acetate or gluconate lozenges may help you get over a cold faster. In one study, people who had early symptoms of a cold took either a lozenge with 13.3 mg of zinc gluconate or placebo. Those who took the zinc saw symptoms, such as coughing, runny nose, and sore throat, disappear faster than those who took placebo. But researchers aren’t sure what type of zinc works best for colds and whether flavorings added to the lozenges might affect how they work.

Zinc nasal sprays are controversial. Some studies have found zinc nasal sprays may help reduce cold symptoms, but other studies have found no effect. In addition, zinc nasal sprays may cause some people to lose their sense of smell. To be safe, talk to your doctor before using a zinc nasal spray.

There is some evidence that zinc supplements (not lozenges) may help lower the risk of getting a cold in the first place. In one study, elderly people in a nursing home who had normal levels of zinc had a lower risk of pneumonia, fewer new antibiotic prescriptions and fewer days of antibiotic use. More and better studies are needed that examine which kinds of zinc may be effective and against which kinds of cold viruses.

Sickle Cell Disease

People who have sickle cell disease are often deficient in zinc. Studies suggest that taking zinc supplements may help reduce symptoms of the disease. Children who took zinc showed improvements in height and weight, and had fewer sickle-cell crises.

Stomach Ulcers

Some studies suggest that zinc may help speed the healing of stomach ulcers. The studies used a form of zinc not available in the U.S.

Attention Deficit Hyperactivity Disorder (ADHD)

For children who have low levels of zinc, some evidence suggests that taking zinc may cause a slight improvement in symptoms, reducing hyperactivity, impulsivity, and impaired socialization in children. However, there was no change in attention deficit symptoms. Zinc may be most helpful to children with a high body mass index, low levels of free fatty acids in their blood, and low levels of zinc.

Herpes simplex (Cold Sores)

Cold sores are caused by the herpes simplex virus. In one study, people with cold sores used either a zinc oxide cream or placebo every 2 hours until their cold sores got better. Those who used the zinc cream had fewer symptoms and got better faster.

HIV/AIDS

It’s common for people with HIV or AIDS to have low levels of zinc, even before symptoms appear. In people with AIDS, low levels of zinc may be a result of poor absorption, medications, and loss of this important nutrient through vomiting or diarrhea. Low levels of zinc can make the body more susceptible to infection, called an opportunistic infection. Some studies show that HIV positive people who take zinc have fewer infections, gain more weight, and have a better immune system response. But not all studies agree, and one even suggests that taking zinc may be associated with higher death rates. If you have HIV or AIDS, talk to your doctor before taking zinc or any supplement.

Wilson's Disease

Preliminary evidence suggests that zinc may help treat Wilson's disease, a condition which causes copper to build up in the body. Because zinc reduces how much copper the body absorbs, it may help reduce levels of copper in people with Wilson's disease.

Other

Other conditions may increase the need for zinc or affect how your body absorbs or uses this mineral. Researchers don’t know, however, whether taking zinc will help treat any of these conditions:

• Acrodermatitis enteropathica (a skin disorder due to an inherited inability to absorb zinc properly)
• Alcoholism
• Cirrhosis (liver disease)
• Kidney disease
• Celiac disease
• Inflammatory bowel disease (ulcerative colitis and Crohn's disease)

Your body absorbs 20 - 40% of the zinc present in food. Zinc from animal foods like red meat, fish, and poultry is more readily absorbed by the body than zinc from plant foods. Zinc is best absorbed when taken with a meal that contains protein.

The best sources of zinc are oysters (richest source), red meats, poultry, cheese (ricotta, Swiss, gouda), shrimp, crab, and other shellfish. Other good, though less easily absorbed, sources of zinc include legumes (especially lima beans, black-eyed peas, pinto beans, soybeans, peanuts), whole grains, miso, tofu, brewer's yeast, cooked greens, mushrooms, green beans, tahini, and pumpkin, and sunflower seeds.

Zinc is available in several forms. Zinc sulfate is the least expensive form, but it is the least easily absorbed and may cause stomach upset.

More easily absorbed forms of zinc are zinc picolinate, zinc citrate, zinc acetate, zinc glycerate, and zinc monomethionine. If zinc sulfate causes stomach irritation, you can try another form, such as zinc citrate.

The amount of elemental zinc is listed on the product label (usually 30 - 50 mg). To determine the amount to take in supplement form, remember that you get about 10 - 15 mg from food.

Zinc lozenges, used for treating colds, are available in most drug stores. There are also nasal sprays developed to reduce nasal and sinus congestion, although they may have some safety issues (see “Precautions”).

You should take zinc with water or juice. If zinc causes stomach upset, it can be taken with meals. Don't take zinc at the same time as iron or calcium supplements.

A strong relationship exists between zinc and copper. Too much of one can cause a deficiency in the other. If you take zinc, including zinc in a multivitamin, you should also take copper.

Do not give zinc supplements to a child without talking to your doctor.

Daily intake of dietary zinc (according to the National Academy of Sciences) are listed below:

Pediatric

• Infants birth - 6 months: 2 mg (AI)
• Infants 7 - 12 months: 3 mg (RDA)
• Children 1 - 3 years: 3 mg (RDA)
• Children 4 - 8 years: 5 mg (RDA)
• Children 9 - 13 years: 8 mg (RDA)
• Boys 14 - 18 years: 11 mg (RDA)
• Girls 14 - 18 years: 9 mg (RDA)

Adult

• Men 19 years and older: 11 mg (RDA)
• Women 19 years and older: 8 mg (RDA)
• Pregnant women 14 - 18 years: 12 mg (RDA)
• Pregnant women 19 years and older: 11 mg (RDA)
• Breastfeeding women 14 - 18 years: 13 mg (RDA)
• Breastfeeding women 19 years and older: 12 mg (RDA)

You should not take high doses of zinc for more than a few days unless your doctor tells you to. Talk to your doctor before taking more than 40 mg of zinc per day and take breaks from zinc supplementation. During those breaks, get zinc from a well-balanced diet.

Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable health care provider.

Research has shown that less than 40 mg a day is a safe amount to take over time, but researchers are not sure what happens if more is taken over a long period. Additional concerns have been raised about combining multivitamins and additional zinc supplements and an increased risk of dying from prostate cancer. Speak with physician.

Taking 100 mg of zinc daily, or taking supplemental zinc for 10 years or longer, has been linked with a doubling of the risk developing prostate cancer in men.

Common side effects of zinc include stomach upset, nausea, vomiting, and a metallic taste in the mouth. High doses of zinc can cause dizziness, headache, drowsiness, increased sweating, loss of muscle coordination, alcohol intolerance, hallucinations, and anemia.

There are reports that a single dose of zinc as high as 10-30 grams can be lethal.

Very high doses of zinc may actually weaken immune function. High doses of zinc may also lower HDL ("good") cholesterol and raise LDL ("bad") cholesterol.

Some people who have used certain zinc nasal sprays to treat a cold have lost their sense of smell. Talk to your doctor before using a zinc nasal spray.

If you are being treated with any of the following medications, you should not use zinc without first talking to your health care provider.

Amiloride (Midamor) -- Amiloride is a potassium-sparing diuretic (water pill) that may increase the levels of zinc in your blood. Do not take zinc supplements if you take amiloride.

Blood pressure medications, ACE Inhibitors -- A class of medications called ACE inhibitors, used to treat high blood pressure, may decrease the levels of zinc in your blood. ACE inhibitors include:

• Benazepril (Lotensin)
• Captopril (Capoten)
• Enalapril (Vasotec)
• Fosinopril (Monopril)
• Lisinopril (Zestril)
• Moexipril (Univasc)
• Perindopril (Aceon)
• Quinapril (Accupril)
• Ramipril (Altace)
• Trandolapril (Mavik)

Antibiotics -- Zinc may decrease your body's absorption of two kinds of antibiotics, quinolones and tetracyclines. These include:

• Ciprofloxacin (Cipro)
• Gatifloxacin (Tequin)
• Levofloxacin (Levaquin)
• Moxifloxacin (Avelox)
• Norfloxacin (Noroxin)
• Ofloxacin (Floxin)
• Demeclocycline (Declomycin)
• Minocycline (Minocin)
• Tetracycline

However, doxycycline (Vibramycin) does not seem to interact with zinc.

Cisplatin (Platinol-AQ) -- This drug, used for chemotherapy to treat some types of cancers, may cause more zinc to be lost in your urine. If you are undergoing chemotherapy, do not take zinc or any other supplement without talking to your oncologist.

Deferoxamine (Desferal) -- This medication, used to remove excess iron from the blood, also increases the amount of zinc that is lost in urine.

Immunosuppressant medications -- Since zinc may make the immune system stronger, it should not be taken with corticosteroids (such as prednisone), cyclosporine, or other medications intended to suppress the immune system.

Penicillamine -- This medication, used to treat Wilson's disease (where excess copper builds up in the brain, liver, kidney, and eyes) and rheumatoid arthritis, decreases the levels of zinc in your blood.

Thiazide diuretics (water pills) -- These medications lower the amount of zinc in your blood by increasing the amount of zinc that is passed in your urine. If you take thiazide diuretics, your doctor will monitor levels of zinc and other important minerals in your blood:

• Chlorothiazide (Diuril)
• Chlorthalidone (Hygroton)
• Hydrochlorothiazide
• Indapamide (Lozol)
• Metolozone (Zaroxolyn)
• Polythiazide (Renese)
• Quinethazone (Hydromox)
• Trichlormethiazide (Metahydrin, Naqua, Diurese)

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