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:
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 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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