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 warn.

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 is better."

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 medical histories.

"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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