Zinc is a nutrient found throughout the body. It helps the body's immune system and metabolism work correctly. Zinc also is important for wound healing and for the sense of taste.

Most people who eat a healthy, varied diet get enough zinc. Zinc can be found in foods such as beef, chicken, fish, seafood, and fortified breakfast cereals.

Some people take a zinc supplement by mouth to help treat colds. But it's important to know that if you take a zinc supplement, it could lessen the effectiveness of some other medicines. And zinc can cause side effects.

Women age 19 and older who are not pregnant should get 8 milligrams (mg) of zinc a day, and men age 19 and older should get 11 mg. The amount of zinc needed every day is different for children and people who are pregnant or breastfeeding. If you have questions about how much zinc you need, talk with your healthcare professional.

Here's what the research shows about zinc that's taken by mouth for the following conditions:

• Zinc deficiency. People who have low levels of zinc seem to benefit most from zinc supplements. Zinc deficiency isn't common in the United States. But some medicines, such as thiazide diuretics taken to treat high blood pressure, can raise the amount of zinc lost in urine. That could lead to zinc deficiency.
• Colds. Research suggests that if zinc syrup or lozenges are taken within 24 hours after cold symptoms start, zinc can help shorten the length of a cold. But the use of zinc that's placed into the nose, called intranasal zinc, has been linked to loss of the sense of smell. Sometimes, the loss of smell may last for a long time. And it's possible that the sense of smell may not come back at all.
• Wound healing. People who have wounds such as skin ulcers and who also have low levels of zinc might benefit from taking a zinc supplement by mouth.
• Diarrhea. Zinc supplements can ease symptoms of diarrhea in children who have low levels of zinc. That may happen in children who have malnutrition. There isn't enough research to recommend use of zinc supplements for children with diarrhea who eat a healthy, varied diet.
• Age-related macular degeneration. Research suggests that zinc supplements taken by mouth might slow the progression of this eye disease.

Zinc that's used on the skin is called zinc oxide. Zinc oxide cream, ointment or paste is put on the skin to prevent conditions such as diaper rash and sunburn.

Zinc supplements taken by mouth may cause:

• Diarrhea.
• Dizziness.
• Headache.
• Nausea.
• Upset stomach.
• Vomiting.

Taking zinc supplements by mouth long-term and in high doses can lead to copper deficiency. People with low copper levels might have brain and nervous system issues. Those issues may include numbness and weakness in the arms and legs.

According to the National Institutes of Health, 40 mg of zinc a day is the upper limit of a daily dose of zinc taken by mouth for all people age 19 and older. For people 18 and younger, the upper daily limit of zinc varies depending on age. If you have questions about how much zinc a child needs, talk with a healthcare professional.

Don't use zinc that's placed in the nose, called intranasal zinc. This form of zinc has been linked to loss of the sense of smell.

A zinc supplement taken by mouth may lead to problems if you're taking the following medicines:

• Antibiotics. Taking a zinc supplement by mouth while you're taking quinolone or tetracycline antibiotics can hinder the antibiotics' ability to fight bacteria. Taking the antibiotic two hours before or 4 to 6 hours after taking zinc can lower this effect.
• Penicillamine (Cuprimine, Depen). Taking a zinc supplement by mouth with the rheumatoid arthritis medicine penicillamine can lower penicillamine's ability to ease arthritis symptoms. Taking zinc at least one hour before or one hour after taking penicillamine can lower this effect.

Talk with your healthcare professional before you start taking a zinc supplement to make sure it's right for you.