| Zinc Supplement Overdose
Can Have Toxic Effects
Prolonged consumption of large doses of over-the-counter mineral
and vitamin supplements--such as the increasingly popular mineral
zinc--can cause major health complications, California researchers
The researchers highlight the case
of a high school basketball player who suffered from extreme fatigue
after taking large amounts of zinc on a daily basis to treat a
chronic skin condition for more than a year and a half.
"In general, these supplements
are safe if the doses that are written on the bottles are followed,"
noted Dr. Mark B. Salzman of Kaiser Permanente West Los Angeles
Medical Center, the study's lead author. "(But) this was a 17-year-old
teenager who felt that since the usual dose was not working, more
In the current issue of the Journal
of Pediatric Hematology/Oncology, Salzman and his colleagues report
that the patient had initially been advised by a dermatologist
to take zinc supplements as an acne treatment. However, when the
teen saw no quick improvement in his skin he decided to up the
dosage from 50 milligrams (mg) per day to 300 mg per day.
After repeatedly witnessing the
teen tire easily when playing basketball, the patient's mother
became concerned that he might have a heart condition and brought
her son in for a series of medical evaluations.
The doctors discovered that the
boy had an abnormally low red blood cell count, or anemia. An
inadequate supply of red blood cells results in a drop in the
delivery of oxygen throughout the body, leading to fatigue, weakness,
dizziness and even heart attack or stroke in some cases.
In addition, the tests revealed
that the teen suffered from neutropenia, a condition in which
the amount of neutrophils in the blood is abnormally low. Neutrophils,
a type of white blood cell, serve as the body's main cellular
defense against infection and play a critical role in healing.
Two weeks after he stopped taking
zinc, the teen's blood levels of the mineral remained two to three
times greater than normal. Salzman and his team concluded that
an overdose of zinc accounted for the blood complications. The
patient was given no medication for treatment, and 4 months after
he had stopped taking zinc he had almost fully recovered.
The researchers observed, however,
that even after 6 months, the patient's zinc levels remained at
slightly above normal levels, and note that zinc elimination is
an extremely slow process. In more severe cases of elevated zinc
levels, they note, a patient may be given copper supplements,
since normal absorption of copper by the body can be blocked by
excessive zinc consumption.
The authors caution that as the
market in vitamin and mineral products is virtually unregulated,
the toxic effects of overdosing may become increasingly common.
They added that zinc, in particular, has grown recently in popularity
as a remedy for the common cold. They urged doctors to be on the
lookout for overuse of zinc or any other minerals when taking
"This may be an isolated case,
but I would think it happens regularly since so may people take
supplements," Salzman told Reuters Health. "The public needs to
know that over-the-counter medications and supplements can have
serious adverse effects when larger than recommended doses are
taken without the advice of a health professional."
SOURCE: Journal of Pediatric Hematology/Oncology 2002;24:582-584.
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