Zinc deficiency most often occurs when zinc intake
is inadequate or poorly absorbed and it can have serious
health consequences. Moderate to severe zinc deficiency
is rare in the United States. However, it is highly
prevalent in developing countries.
The symptoms of
severe deficiency include the slowing or cessation of
growth and development, delayed sexual maturation,
skin rashes, chronic and severe diarrhea, immune system
deficiencies, poor wound healing, decreased appetite,
impaired taste sensation, night blindness, swelling
and clouding of the corneas, and behavioral disorders.
These symptoms were first accurately described
when a genetic disorder called acrodermatitis enteropathica
was linked to zinc deficiency.
Although
mild dietary zinc deficiency is unlikely to cause such
severe symptoms, it is known to contribute to several
health problems, especially in young children. Zinc
deficiency leads to impaired physical and neuropsychological
development, and to an increased risk of
life–threatening infections in young children. Individuals
at risk of zinc deficiency include:
-infants and children
-pregnant and breastfeeding women, especially
teenagers
-patients receiving intravenous feeding
-malnourished individuals, including those with anorexia
nervosa
-people with severe or persistent diarrhea
-people with malabsorption syndromes, including celiac
disease and short bowel syndrome
-people with inflammatory bowel disease, including
Crohn’s disease and ulcerative colitis
-people with alcoholic liver disease
-people with sickle cell anemia
-elderly people
-strict vegetarians whose major food staples are grains
and legumes because the high levels of phytic acid in
these foods lower the absorption of zinc
Fortified foods include many types of breakfast
cereals that make it easier to consume the RDA for
zinc. However, they also make it easier to consume too
much zinc, especially if zinc supplements are also
taken. Anyone considering zinc supplementation
should accordingly first consider whether their needs
could be met by dietary zinc sources and from fortified
foods.
Intakes between 150 and 450 mg of zinc per day
lead to copper deficiency, impaired iron function,
reduced immune function, and reduced levels of
high-density lipoproteins, the ‘‘good cholesterol’’. A
few isolated cases of acute zinc toxicity have been
reported for food or beverages contaminated with
zinc present in galvanized containers. Single doses of
225–450 mg of zinc are known to induce vomiting.
Milder gastrointestinal distress has been reported at
doses of 50–150 mg/day of supplemental zinc.
In the case of zinc deficiency, oral zinc therapy
usually results in the complete disappearance of symptoms,
but it must be maintained indefinitely in individuals
with the acrodermatitis enteropathica.
Excessive intake can be corrected by bringing levels
back to the RDA values.
It has been estimated that 82% of pregnant
women worldwide are likely to have inadequate zinc
intakes. Zinc deficiency has been associated with a
number of pregnancy complications, including low
birth weight, premature delivery, and labor and delivery
complications.
The adverse effects of zinc deficiency on immune
system function are also likely to increase complications
in children that have infectious diarrhea. Persistent
diarrhea contributes to zinc deficiency and
malnutrition. Recent research has shown that zinc
deficiency may also increase the harmful effects of
toxins produced by diarrhea-causing bacteria like
E. coli. Zinc supplementation in combination with
drinking plenty of liquids has also been shown to
significantly reduce the duration and severity of childhood
diarrhea.
Significant delays in growth and weight gain,
known as growth retardation or failure to thrive, are
common symptoms of mild zinc deficiency in children.
But since many of the symptoms associated with zinc
deficiency are general and also observed with other
medical conditions, parents should not assume that
they are due to a zinc deficiency. It is important to
consult with a health care professional concerning medical
symptoms so that appropriate care can be given.
