We read with interest the paper by Mossad and colleagues [1] on the use of zinc gluconate for treating colds. However, we were concerned by the authors' statement that "individual patients must decide whether the possible beneficial effects of zinc gluconate on cold symptoms outweigh the possible adverse effects." In the United States, approximately 1 million persons are hemochromatosis homozygotes; in most persons, however, this condition is not diagnosed. An estimated 25 million persons are hemochromatosis heterozygotes. In most homozygotes and some heterozygotes, the gastrointestinal absorption of iron, cobalt, and lead is increased [2]. In homozygotes, the hepatic retention of zinc is increased fivefold, an effect apparently unassociated with the presence or absence of hepatic cirrhosis [3]. In homozygotes, whole-body zinc excretion is normal or increased [4]. These observations suggest that zinc absorption is also increased in hemochromatosis.

Mossad and coworkers chose zinc gluconate because of its high degree of bioavailability. Zinc absorption and retention from this medication may be increased in persons with hemochromatosis alleles. Serum zinc concentrations are usually normal in persons with hemochromatosis [5] and thus are unreliable indicators of zinc nutriture. Copper depletion is the only known consequence of excess zinc absorption in humans, but other ill effects may await discovery. Further, little information exists about the role of zinc in the causation or alleviation of liver or other tissue injury in patients who have hemochromatosis, with or without iron overload. However, use of zinc to treat colds may be uncontrolled because absorbable zinc salts are available without prescription; some patients may repeatedly use these salts as cold treatments. Until further investigations demonstrate the long-term safety of therapy with zinc gluconate, we believe it is imprudent for persons known to be hemochromatosis homozygotes or heterozygotes to use zinc salts to treat colds.