Why Zinc Should Be In YOur Diet
Zinc has been known for more than 50 years to be an essential
mineral. It is found in almost every cell in the body and is required
for for biochemical reactions of more than 300 enzymes, covering all
six classes of enzymes. Zinc is important for a healthy immune system,
for healing cuts and wounds, and for maintaining your sense of taste
and smell. The body needs zinc for normal growth and health. Zinc also
supports normal growth and development during pregnancy, childhood, and
adolescence.
Meat and poultry provide the majority of zinc in the American diet.
Other food sources include seafood (especially herring and oysters),
peas, and beans. Zinc is also found in whole grains; however, large
amounts of whole-grains have been found to decrease the amount of zinc
that is absorbed. Oysters are the food containing the most zinc by
weight, but beef is a more common source in the U.S. diet. The zinc
found in meat and oysters is easily absorbed by the body. Dietary
phytates, which are found in whole grain cereals and unleavened bread,
may significantly decrease the body's absorption of zinc. Additional
zinc may be added to the diet through treated (galvanized) cookware.
Foods stored in uncoated tin cans may cause less zinc to be available
for absorption from food.
Results of two national surveys, the National Health and Nutrition
Examination Survey (NHANES III 1988-91) and the Continuing Survey of
Food Intakes of Individuals (1994 CSFII) indicated that the diets of
many adults, especially older Americans and women, do not provide the
recommended amounts of zinc.
Zinc deficiency can occur when zinc intake is inadequate, when there
are increased losses of zinc from the body, or when the body's
requirement for zinc increases. There is no specific deficiency disease
associated with zinc. Instead, many general signs of zinc deficiency
can appear, including poor appetite, weight loss, poor night vision,
delayed healing of wounds, a decrease in sense of taste and smell, poor
development of reproductive organs and mental lethargy. As body stores
of zinc decline, these symptoms worsen and are accompanied by diarrhea,
hair loss, recurrent infection, and a form of dermatitis, a skin
disorder. Zinc deficiency has also been linked to poor growth in
childhood.
Zinc supplements are used to prevent or treat zinc deficiency.
For patients who are unable to get enough zinc in their regular diet
or who have a need for more zinc, zinc supplements may be necessary.
They are generally taken by mouth but some patients may have to receive
them by injection.
People who may benefit from a zinc supplement include those who do
not consume enough calories, vegetarians, the elderly, pregnant and
lactating women, and people who suffer from alcoholism or digestive
diseases that cause diarrhea.
Anyone with a low caloric intake is at higher risk for having a low
zinc intake and for developing a zinc deficiency. Vegetarians who
consume a variety of legumes and nuts will probably meet their zinc
requirement, but otherwise a vegetarian diet may be inadequate in zinc.
Since the zinc from plant sources is absorbed less readily, this
increases the concern about zinc status in vegetarians who do not
consume legumes and nuts.
Dietary surveys suggest that many Americans aged 51 and older,
pregnant women and breastfeeding mothers do not consume recommended
amounts of zinc. Therefore, to decrease their risk for developing a
zinc deficiency, it is important for individuals in these groups to
include sources of zinc in their daily diet. Zinc supplementation has
been found to improve the growth rate in children with mild zinc
deficiency and mild to moderate growth failure. Maternal zinc
deficiency can delay fetal growth, and mothers who give birth to small
for gestational age babies have been found to have lower zinc intakes
during pregnancy. Breastfeeding increases the risk of depleting
nutritional zinc status when dietary zinc intake is chronically low
because of the greater need for zinc during lactation.
Zinc deficiency is frequently associated with alcoholism, which is
often due to a lower intake of food. The need for a supplement as part
of an overall treatment plan is usually evaluated by a physician in
this situation.
Diarrhea causes a loss of zinc. Therefore, digestive diseases or
gastrointestinal surgery that result in diarrhea are often associated
with zinc deficiency. Individuals who experience chronic diarrhea
should make sure they include sources of zinc in their daily diet. A
medical doctor can evaluate the need for a zinc supplement if diet
alone fails to maintain normal zinc levels in the body.
Zinc supplements may be used for other conditions as determined by your health care professional.
Some conditions may increase your need for zinc. These include:
In addition, premature infants may need additional zinc and zinc
supplements are used in certain patients with the following medical
condition:
Increased need for zinc should be determined by your health care professional.
The immune system is adversely affected by even moderate degrees of
zinc deficiency. People who are zinc-deficient have a more difficult
time resisting infections. T-cell lymphocytes, white blood cells that
help fight infection, do not function efficiently when zinc stores are
low. When zinc supplements are given to individuals with low zinc
levels, the numbers of T-cell lymphocytes circulating in the blood
increase and the ability of lymphocytes to fight infection improves.
Studies show that poor, malnourished children in India, Africa, South
America, and Southeast Asia experience shorter courses of infectious
diarrhea after taking zinc supplements. Zinc supplements are often used
to treat skin ulcers or bed sores , but they do not increase rates of
wound healing when zinc levels are normal.
A study of over 100 employees of the Cleveland Clinic indicated that
zinc lozenges decreased the duration of colds by one-half. Some of the
participants reported fewer days of congestion and nasal drainage, but
no differences were seen in how long their fevers lasted or in the
level of muscle aches they experienced. However, this study has been
criticized by some researchers who believe that since zinc lozenges
often have a bad taste, the participants may have known the difference
between the supplement and placebo, which would compromise the results.
Also, since other studies have shown no benefit the debate continues on
the true value of zinc supplements for cold symptoms.
Iron deficiency anemia is considered a serious public health problem
in the world today. Iron fortification programs were developed to
prevent this deficiency and they have been credited with improving the
iron status of millions of women, infants, and children. Some
researchers, however, have raised concern about the effects of iron
fortification on other nutrients, including zinc. Iron taken in
solution can inhibit the absorption of zinc, but foods fortified with
iron do not.
Zinc supplements are most effective if they are taken at least 1
hour before or 2 hours after meals. However, if zinc supplements cause
stomach upset, they may be taken with a meal. You should tell your
health care professional if you are taking your zinc supplement with
meals.
The health risk of taking too much zinc is moderate to high. Zinc
toxicity has been seen in both acute and chronic forms. Intakes of 150
to 450 mg of zinc per day have been associated with low copper status,
altered iron function, reduced immune function, and reduced levels of
high-density lipoproteins (the good cholesterol). One case report cited
severe nausea and vomiting within 30 minutes after the person ingested
four grams of zinc gluconate (570 mg elemental zinc). The 1989 RDA
committee stated that "chronic ingestion of zinc supplements exceeding
15 mg/day is not recommended without adequate medical supervision." The
National Academy of Sciences is currently reviewing recent research and
considering new recommendations on zinc intake and risk.
Zinc has been known for more than 50 years to be an essential
mineral. It is found in almost every cell in the body and is required
for for biochemical reactions of more than 300 enzymes, covering all
six classes of enzymes. Zinc is important for a healthy immune system,
for healing cuts and wounds, and for maintaining your sense of taste
and smell. The body needs zinc for normal growth and health. Zinc also
supports normal growth and development during pregnancy, childhood, and
adolescence.
Meat and poultry provide the majority of zinc in the American diet.
Other food sources include seafood (especially herring and oysters),
peas, and beans. Zinc is also found in whole grains; however, large
amounts of whole-grains have been found to decrease the amount of zinc
that is absorbed. Oysters are the food containing the most zinc by
weight, but beef is a more common source in the U.S. diet. The zinc
found in meat and oysters is easily absorbed by the body. Dietary
phytates, which are found in whole grain cereals and unleavened bread,
may significantly decrease the body's absorption of zinc. Additional
zinc may be added to the diet through treated (galvanized) cookware.
Foods stored in uncoated tin cans may cause less zinc to be available
for absorption from food.
Results of two national surveys, the National Health and Nutrition
Examination Survey (NHANES III 1988-91) and the Continuing Survey of
Food Intakes of Individuals (1994 CSFII) indicated that the diets of
many adults, especially older Americans and women, do not provide the
recommended amounts of zinc.
Zinc deficiency can occur when zinc intake is inadequate, when there
are increased losses of zinc from the body, or when the body's
requirement for zinc increases. There is no specific deficiency disease
associated with zinc. Instead, many general signs of zinc deficiency
can appear, including poor appetite, weight loss, poor night vision,
delayed healing of wounds, a decrease in sense of taste and smell, poor
development of reproductive organs and mental lethargy. As body stores
of zinc decline, these symptoms worsen and are accompanied by diarrhea,
hair loss, recurrent infection, and a form of dermatitis, a skin
disorder. Zinc deficiency has also been linked to poor growth in
childhood.
Zinc supplements are used to prevent or treat zinc deficiency.
For patients who are unable to get enough zinc in their regular diet
or who have a need for more zinc, zinc supplements may be necessary.
They are generally taken by mouth but some patients may have to receive
them by injection.
People who may benefit from a zinc supplement include those who do
not consume enough calories, vegetarians, the elderly, pregnant and
lactating women, and people who suffer from alcoholism or digestive
diseases that cause diarrhea.
Anyone with a low caloric intake is at higher risk for having a low
zinc intake and for developing a zinc deficiency. Vegetarians who
consume a variety of legumes and nuts will probably meet their zinc
requirement, but otherwise a vegetarian diet may be inadequate in zinc.
Since the zinc from plant sources is absorbed less readily, this
increases the concern about zinc status in vegetarians who do not
consume legumes and nuts.
Dietary surveys suggest that many Americans aged 51 and older,
pregnant women and breastfeeding mothers do not consume recommended
amounts of zinc. Therefore, to decrease their risk for developing a
zinc deficiency, it is important for individuals in these groups to
include sources of zinc in their daily diet. Zinc supplementation has
been found to improve the growth rate in children with mild zinc
deficiency and mild to moderate growth failure. Maternal zinc
deficiency can delay fetal growth, and mothers who give birth to small
for gestational age babies have been found to have lower zinc intakes
during pregnancy. Breastfeeding increases the risk of depleting
nutritional zinc status when dietary zinc intake is chronically low
because of the greater need for zinc during lactation.
Zinc deficiency is frequently associated with alcoholism, which is
often due to a lower intake of food. The need for a supplement as part
of an overall treatment plan is usually evaluated by a physician in
this situation.
Diarrhea causes a loss of zinc. Therefore, digestive diseases or
gastrointestinal surgery that result in diarrhea are often associated
with zinc deficiency. Individuals who experience chronic diarrhea
should make sure they include sources of zinc in their daily diet. A
medical doctor can evaluate the need for a zinc supplement if diet
alone fails to maintain normal zinc levels in the body.
Zinc supplements may be used for other conditions as determined by your health care professional.
Some conditions may increase your need for zinc. These include:
- Acrodermatitis enteropathica (a lack of absorption of zinc from the intestine)
- Alcoholism
- Burns
- Diabetes mellitus (sugar diabetes)
- Down's syndrome
- Eating disorders
- Intestine diseases
- Infections (continuing or chronic)
- Kidney disease
- Liver disease
- Pancreas disease
- Sickle cell disease
- Skin disorders
- Stomach removal
- Stress (continuing)
- Thalassemia
- Trauma (prolonged)
In addition, premature infants may need additional zinc and zinc
supplements are used in certain patients with the following medical
condition:
- Wilson's disease (a disease of too much copper in the body)
Increased need for zinc should be determined by your health care professional.
Zinc, infections, and wound healing
The immune system is adversely affected by even moderate degrees of
zinc deficiency. People who are zinc-deficient have a more difficult
time resisting infections. T-cell lymphocytes, white blood cells that
help fight infection, do not function efficiently when zinc stores are
low. When zinc supplements are given to individuals with low zinc
levels, the numbers of T-cell lymphocytes circulating in the blood
increase and the ability of lymphocytes to fight infection improves.
Studies show that poor, malnourished children in India, Africa, South
America, and Southeast Asia experience shorter courses of infectious
diarrhea after taking zinc supplements. Zinc supplements are often used
to treat skin ulcers or bed sores , but they do not increase rates of
wound healing when zinc levels are normal.
Zinc and the common cold
A study of over 100 employees of the Cleveland Clinic indicated that
zinc lozenges decreased the duration of colds by one-half. Some of the
participants reported fewer days of congestion and nasal drainage, but
no differences were seen in how long their fevers lasted or in the
level of muscle aches they experienced. However, this study has been
criticized by some researchers who believe that since zinc lozenges
often have a bad taste, the participants may have known the difference
between the supplement and placebo, which would compromise the results.
Also, since other studies have shown no benefit the debate continues on
the true value of zinc supplements for cold symptoms.
Zinc and iron absorption
Iron deficiency anemia is considered a serious public health problem
in the world today. Iron fortification programs were developed to
prevent this deficiency and they have been credited with improving the
iron status of millions of women, infants, and children. Some
researchers, however, have raised concern about the effects of iron
fortification on other nutrients, including zinc. Iron taken in
solution can inhibit the absorption of zinc, but foods fortified with
iron do not.
Zinc supplements are most effective if they are taken at least 1
hour before or 2 hours after meals. However, if zinc supplements cause
stomach upset, they may be taken with a meal. You should tell your
health care professional if you are taking your zinc supplement with
meals.
The health risk of taking too much zinc is moderate to high. Zinc
toxicity has been seen in both acute and chronic forms. Intakes of 150
to 450 mg of zinc per day have been associated with low copper status,
altered iron function, reduced immune function, and reduced levels of
high-density lipoproteins (the good cholesterol). One case report cited
severe nausea and vomiting within 30 minutes after the person ingested
four grams of zinc gluconate (570 mg elemental zinc). The 1989 RDA
committee stated that "chronic ingestion of zinc supplements exceeding
15 mg/day is not recommended without adequate medical supervision." The
National Academy of Sciences is currently reviewing recent research and
considering new recommendations on zinc intake and risk.
- Zinc Supplements. U.S. National Library of Medicine. Medlineplus.
- Facts about Dietary Supplements, Zinc. NIH Office of Dietary Supplements
- Sandstead HH. Understanding zinc: Recent observations and interpretations. J Lab Clin Med 1994;124:322-7.
- Heyneman CA. Zinc deficiency and taste disorders. Ann Pharmacother 1996;30:186-7.
- Fabris N and Mocchegiani E. Zinc, human diseases and aging. Aging (Milano) 1995;7:77-93.
- Gibson RS. Content and bioavailability of trace elements in vegetarian diets. Am J Clin Nutr 1994;59:1223S-1232S.
- Prasad AS. Zinc deficiency in women, infants and children. J Am Coll Nutr 1996;15:113-20.
- Garland ML, Hagmeyer KO. The role of zinc lozenges in treatment of the common cold. Ann Pharmacother 1998;32:63-9.
- Whittaker P. Iron and zinc interactions in humans. Am J Clin Nutr 1998;68:442S-446S.
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