Feb. 19, 2001 -- When a cold bug begins making the rounds in her family of 10, Barbara Rennard does what her mother and her mother's mother did: She cooks up a batch of chicken soup.
"It's a wonderful recipe from her Jewish grandmother, who was convinced it helped fight colds," says her husband, Stephen Rennard, MD.
Mothers everywhere have been offering chicken soup to cold suffers for centuries, of course. The Jewish physician and philosopher Maimonides recommended it way back in the 12th century. And there's evidence that even the ancient Greeks were quick to help themselves to chicken soup at the first sign of a cold.
"I've heard it a zillion times from patients," says Stephen Rennard. "So finally my wife and I decided to put it to the test."
The results of their experiment, published in the October 2000 issue of the journal Chest (along with a recipe for Grandma's soup), support once again that age-old advice: listen to your mother.
Chicken Soup for Your Immune System
The Rennards aren't the first researchers to test the chicken soup cure. In an October 1978 article published in the same journal, scientists reported that sipping hot chicken soup did indeed help clear up clogged nasal passages. But they also found that sipping just plain hot water could clear stuffy noses -- suggesting that the benefit comes simply from inhaling hot water vapor. Even so, chicken soup still proved to be more effective than hot water in this earlier experiment (not to mention more satisfying).
Enter the Rennards. "If chicken soup really does make a difference, we figured it might do so by affecting the inflammatory system," says Stephen Rennard. It turns out, he says, that the sniffles and sneezes of a cold aren't caused directly by cold viruses but rather by the inflammatory system's response to the virus. The viral infection triggers localized inflammation, which produces the characteristic congestion of a head cold.
To find out if chicken soup directly affected one of the kinds of cells involved in that inflammation, the Rennards and their colleagues at the University of Nebraska cooked up batches of Grandma's soup in the lab. Then they collected inflammatory cells called neutrophils from blood samples taken from a group of healthy volunteers. Finally, they exposed the cells to diluted broth from the soup.
Sure enough, the diluted broth slowed the movement of the cells involved in causing congestion. "The study was done in the laboratory. However, if the same thing happened in the body, by inhibiting the migration of these cells in sinus passages, we think chicken soup may in fact reduce the symptoms of a stuffy nose from a cold," says Stephen Rennard.
Canned vs. Homemade
Exactly what components in the chicken soup might be responsible remains a mystery. Broth simmered only a short time was less effective at slowing neutrophil migration than soup that had been on the stove longer. But whether the magic ingredient comes from the chicken itself or the vegetables in the recipe remains an open question.
Happily, in this season of sniffles and sneezes, you can test the cold-fighting power of Grandma's soup yourself. (See recipe below.)
If you're feeling too sick to cook up a pot of homemade soup, never fear. Many canned versions appear to work just as well, the researchers found. The Rennards purchased 13 different soups from their local market and tested them against Grandma's recipe. All but two proved just as effective in inhibiting immune cell migration as the family's traditional recipe. In fact -- don't tell Grandma -- five of the commercial soups actually were more effective. But none of them, Stephen Rennard is quick to report, came even close to being as delicious.