Oct. 17, 2000 -- Run, chicken, run! From the plains of Nebraska comes evidence to uphold a mother-hen myth: Chicken soup, prepared with a variety of vegetables, has been scientifically shown to inhibit a process that leads to the respiratory symptoms seen with the common cold -- and just in time for cold season.
Researchers at the Nebraska Medical Center in Omaha came up with this conclusion after first preparing and testing a homemade chicken soup containing a whole chicken and additional wings, onions, sweet potato, parsnips, turnips, carrots, celery, and parsley. After cooking for a couple of hours, the chicken was removed and not used any further. The vegetables, meantime, were passed through a food processor and strained, then returned to the broth.
Healthy, nonsmoking volunteers made up the study subjects -- or rather, their blood did -- because the experiment was strictly done outside the body: No one ate the soup. Samples were collected, and neutrophils, a type of white blood cell important in defending the body against infections, were obtained from the volunteers' blood. "Neutrophils are responsible for migrating to sites where the body has been invaded [by germs]," says lead author Stephen Rennard, MD. "They eat germs and kill them." What draws them to those invaded sites are chemicals called 'chemotactic factors.' The whole reaction leads to inflammation -- and in the case of a cold, symptoms such as coughing."
To test the effect of the chicken soup, the researchers separated the chemotactic factors and neutrophils in a lab. After mixing the soup with the neutrophils, they checked to see whether it stopped the cells' tendency to move toward the chemotactic factors. If the soup worked, inflammation would not take place, and the symptoms of a cold might be avoided. The overall conclusion: Chicken soup inhibits neutrophil movement toward chemotactic factors. In other words, soup is good for a cold.
"There very clearly are medicinal or biologically active compounds in the soup. There's really no surprise. The vegetables we used are known to be chock full of active compounds," says Rennard. "To be right, we shouldn't say anything about what people should do in real life. However, if your grandmother always said you should take chicken soup when you have a cold, this would be data that could provide theoretical evidence to support that."
And how much soup should you eat in order to feel better? Well, Rennard and his colleagues can't really say. But, they did check the power of the brew at various dilutions. "We could detect an effect at a 1:200 dilution," he says, "which corresponds with [the volume of] one bowl diluted into the total body volume. But, we have no idea whether the active compounds in soup are even absorbable." Another interesting tidbit about the soup: Rennard says the complete soup wasn't harmful to cells -- even though some of the vegetables alone mildly were.
"Grandma's soup," as the researchers called it, was a bit unusual in that it contained that many different vegetables. Would other chicken soups work? Thirteen supermarket-bought brands were put to the test. Five -- made by Knorr, Campbell's, Lipton, and Progresso -- worked as well as Grandma's concoction at taming neutrophil activity. But, don't go looking for an effect from Campbell's Ramen noodle, chicken flavor. Even tap water worked better.
The authors say other things may contribute to the seemingly positive effect of chicken soup on cold sufferers. Sipping warm liquid can help clear the nose. The healing atmosphere surrounding the serving of chicken soup may exert a placebo effect. And, particles in soup can physically affect neutrophils. Still, a clear, strained version of Grandma's soup did work -- leading the researchers to hypothesize that chicken soup is quite possibly a brew with medical significance.
Others were impressed with the quality of the research behind what might seem a wacky theory. "This study showed it did have a mild, anti-inflammatory effect," says Alan Plummer, MD, chief of pulmonary and critical care at Emory University Hospital in Atlanta. He does caution, though, that chicken soup, helpful as it might be, isn't a cure for anything.
Respiratory therapist Bill Gutman, president of the Georgia Society for Respiratory Care, says he would suggest that some patients give it a try. "This says it may actually keep inflammation down," he says. "It certainly makes sense."