April 10, 2016

Are You Getting These Nutrients? - Part 14

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.

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.

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.

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

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 a 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.

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