In 1979, Karen Eby, a 3-year-old in Austin, Tex., was taking zinc gluconate as a dietary supplement because she had leukemia and -- like many leukemic youngsters -- was deficient in zinc. One day, when she was coming down with a cold, she refused to swallow the tablet and insisted on letting it melt in her mouth.

It was to change her father's life.

When Karen's sneezes, sniffles and scratchy throat vanished within hours, George Eby, an urban planner, couldn't help noticing. Had the child stumbled onto an important discovery? Or was this merely a fluke?

Eby dug into the considerable scientific literature on the healing properties of zinc and brought his findings to the attention of Dr. William Halcomb, the family's general practitioner, and nutritional scientist Dr. Donald Davis from the University of Texas' Clayton Foundation Biochemical Institute in Austin. At first, the three men used the compound on themselves when they had colds and gave it to relatives and friends. The results were so consistently promising that when Eby inherited some money, the trio recruited some cold sufferers for a more rigorously scientific trial.

Participants were volunteers who, without knowing which was which, took either actual zinc gluconate tablets or placebos -- look-alike dummy lozenges. Ideally, these human guinea pigs would also have been tested to be sure they were actually infected with rhinoviruses -- the known cause of common colds -- but Eby and his colleagues could not afford to hire a microbiologist to do the analyses. However, Halcomb examined the recruits and disqualified those he suspected might have allergies or bacterial infections rather than bona fide colds.

Each volunteer was given either a seven-day supply of 180-milligram zinc gluconate tablets (each containing 23 milligrams of zinc) or an equivalent number of placebos. They were instructed to suck on them for at least 10 minutes to bring the tablets' contents into direct contact with the tissues of the throat where rhinoviruses replicate. (Cold viruses also spawn in the nasal passages, and Eby, Halcomb and Davis had earlier informally tried zinc nose drops and zinc nasal sprays. At effective concentrations, both were painful, and when diluted until they did not burn, they also did not work.)

Adults and youngsters weighing 60 pounds or more took two tablets at the outset, then one every two hours for as long as they were awake, but never more than 12 tablets a day for the adults and nine for the youngsters. For smaller children, the dosage was halved and six tablets a day was the limit. All were instructed to do nothing else for their colds for the duration of the study and to stop treatment entirely six hours after symptoms disappeared.

Because very few of the 146 participants embarked on the experiment with brand-new colds, the results weren't as dramatic as with young Karen. Still, test subjects who had actually used zinc gluconate were symptom-free in an average of 3.9 days, while it was typically 10.8 days before the placebo users were well again.

The researchers reported in the journal Antimicrobial Agents and Chemotherapy last year that, no matter how severe the cold, subjects receiving the zinc typically got better seven days sooner than those who received the placebo.

"It didn't matter," says Eby, "whether people had bad colds or mild ones or how long they had them when they entered our study; they got well about seven days earlier than they would have normally." TT he publication of that first report has brought Eby, its senior author, letters T and inquiries from all over the world. It has also brought him a venture capitalist of sorts, J.C. Godfrey, an organic chemist associated with the Center for Concept Development, a New York marketing research firm.

Godfrey has arranged, with the Food and Drug Administration's approval, to have a group of Florida physicians repeat the study that Eby, Halcomb and Davis conducted in Texas. If these physicians get similar results, more than two dozen other studies will be launched to be certain that zinc gluconate is not only effective against colds, but also safe.

"Among the things we need to nail down in order to get the FDA's ultimate approval," says Godfrey, "is what the ideal dose is and whether there are some people for whom zinc gluconate may be hazardous. George chose the 23-milligram dose arbitrarily, because that is what Karen had been taking, but we really don't know whether a smaller dose would work just as well or a larger one would work even better. And, oh yes, there's the matter of zinc gluconate's bitter taste."

Some people find this taste merely unpleasant, but 12 of the 83 Texas volunteers who took zinc gluconate felt sick to their stomachs and two of these actually threw up. Godfrey, who has served as a flavor consultant to major food companies, has come up with several formulations -- one of them sugar-free -- that make the tablets taste like hard candy. Nonetheless, it is still uncertain whether the tablets will retain their apparent effectiveness if they are also made palatable. MM eanwhile, back in Austin, two things have happened. One is that M Karen Eby, now 8, has recovered from her leukemia. The other is that her father has set up George Eby Research Inc. -- a nonprofit, tax-exempt public charity to delve further into the therapeutic potential of zinc. Eby has been notified that his patent of a zinc gluconate lozenge to shorten the duration of colds will be issued Jan. 22. Assuming the lozenges eventually win FDA approval, sales will help to fund further research.

Still, full FDA approval will probably take at least three years, and Eby is already champing at the bit. If he can get funding, he plans to launch studies that will pit zinc against herpes viruses -- both genital and oral -- and then to probe further the common metal's alleged ability to detoxify insect stings and snake bites and relieve menstrual cramps.

Even this tall order will, says Eby, barely scratch the surface of zinc's potential since there are also reports in the scientific literature of its activity against dozens of other viruses. Zinc may be good for boosting the aging immune system and for treating certain types of prostate gland inflamation.

"I intend to stay in medical research," he says. "True, I don't have scientific credentials. But you don't have to be highly trained in medicine to offer leadership."