DAVID GREENE, HOST:
We are in the midst of this coronavirus outbreak, but it's also worth pointing out that most people in the United States who are sick with a viral illness have something else. One likely suspect - the old fashioned common cold, which does a pretty reliable job of making us feel miserable. NPR's Allison Aubrey reports on one type of cold medicine, zinc lozenges. Can they really shorten the length of a cold?
ALLISON AUBREY, BYLINE: Back in the early 1960s, a young physician named Ananda Prasad studied a group of young Egyptian men who were completely deficient in zinc. They suffered from stunting and had not grown to a normal height. Prasad is now 91 years old and is still a researcher at Wayne State University. He told me that when he gave the young men zinc, something remarkable happened.
ANANDA PRASAD: They grew at a rate of five to six inches in height the first year.
AUBREY: He says he was stunned.
PRASAD: I couldn't believe it.
AUBREY: Lots of scientists questioned his findings, but eventually, in 1974, the National Academy of Sciences declared zinc an essential mineral for human health and established a recommended daily intake. Prasad felt vindicated.
PRASAD: Absolutely. Absolutely (laughter).
AUBREY: What came next may be just as surprising. Prasad knew that zinc had an effect on immunity, so he theorized it may help shorten the duration and symptoms of the common cold. To test this theory, he collaborated with a scientist named Thomas Fitzgerald at the University of Michigan, who says he was very skeptical.
JAMES THOMAS FITZGERALD: I got to admit, when I first heard this, I actually told us this research assistant, I think he's losing it.
AUBREY: But he agreed to help conduct a study. They recruited a bunch of people in Detroit who had colds and gave them zinc lozenges made by a pharmacist. It was a double-blind, placebo-controlled trial, so neither the participants nor the researchers knew who was getting the real thing and who was getting the placebo.
FITZGERALD: Lo and behold, when I did the analysis, it indeed did shorten common cold symptoms by about two or three days. And I got admit, I was stunned by that result.
AUBREY: Several other studies have confirmed these findings, and Harri Hemila of the University of Helsinki in Finland has reviewed all of them. He says low doses don't work, but taking about 80 to 90 milligrams of zinc per day at the onset of a cold is shown to help shorten it. He says he now uses zinc.
HARRI HEMILA: And I'm also encouraging my patients to try zinc.
AUBREY: But here's the caveat, and it's a big one - in the U.S., many zinc lozenges don't contain enough zinc, and many have a bunch of ingredients that can undercut the effectiveness. For instance, some contain citric acid, which binds with the zinc and makes it completely ineffective. Thomas Fitzgerald says the lozenges used for the original study are not commercially available.
FITZGERALD: It was specially designed for the study.
AUBREY: So the rule of thumb is do your homework - check your ingredients and doses because not all products are going to help.
Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.