By Rachel Johnson, Ph.D, M.P.H., R.D., March/April 2007
Before she became a full-time mom, my mother was a registered nurse. It was a career she had been proud of and whenever my sister or I got sick, she jumped right back into that role, doing everything short of donning her starched white nursing cap. She’d examine the thermometer critically and shake it down with a crack of her wrist, and announce, “You’ll be spending the day in bed!” No child could have been better cared for. A glass of ginger ale (with a bendy straw) was always placed in easy reach. And I can still taste her chicken soup, with its perfectly cooked noodles.
Mom was following a timeless tradition: people have always looked to food as medicine. This cold and flu season, I decided to look into the beliefs long held by my mom and many others to see which are nutritionally valid and which are merely folklore.
It turns out there is something to chicken soup after all. In one study, researchers measured nasal mucus velocity (science-speak for “runny nose”) and nasal airflow resistance (stuffy nose) after volunteers drank cold water, hot water or chicken soup. Of the three, hot chicken soup was the most effective at making noses run—a good thing since nasal secretions help rid the body of pathogenic viruses and bacteria. Like any hot liquid, soup also helps hydration and raises the temperature of the airways, both important for loosening secretions. Adding a few hot chiles might help loosen things up even more.
Ever since biochemist Linus Pauling proposed megadoses of vitamin C to stave off cold symptoms, research has been piling up to assess its effectiveness. For perspective, I turned to a well-regarded review of 29 studies that involved more than 11,000 participants. The reviewers found that vitamin C failed to reduce the incidence of colds. But overall, with doses of 200 mg or greater (more than twice the 60-75 mg current recommended dietary intake for adults), the duration of colds was shortened by about 8 percent—not a huge difference, but something. There was also a significant reduction in the number of days subjects took off from work or school, which suggests vitamin C might help reduce a cold’s severity. The likelihood of success seems to vary with the person—some people improve after taking vitamin C supplements, others don’t. Try it and see for yourself but don’t exceed 2,000 milligrams per day. More than this can cause an upset stomach.
Zinc’s effectiveness against cold symptoms is more controversial. One study found that zinc lozenges shortened the duration of colds by one-half, while others found no advantage over a placebo. If you want to try zinc lozenges, follow the protocol used in scientific studies: take the lozenges every two hours and stop when your symptoms die down. Don’t assume more is better; excessive doses of zinc can interfere with the absorption of other minerals, and high doses can be toxic.
Since colds and flu tend to strike during the darker winter months, some researchers believe a lack of vitamin D, the “sunshine” vitamin, might have something to do with making us more susceptible. At least one study found that a group of kids who took vitamin D supplements had fewer colds than another group that didn’t. There’s still much to learn, but unless you get steady exposure to the sun in the winter it seems prudent to take a multivitamin that contains 100 percent of the daily value for vitamin D.
Some people avoid dairy products because they are thought to increase mucus secretions, but scientific evidence has yet to support this. There may be some placebo effect at work: interestingly, people who say they believe that milk causes more mucus production tend to report more respiratory symptoms after they’re given milk. But in a blind test using a soy-based drink with similar sensory characteristics as milk, subjects reported the same changes in mucus production as they did with cow’s milk. Don’t skimp on calcium-rich milk and especially not yogurt, which contains beneficial bacteria that may actually stimulate the immune system.
Today, I wonder if my mother would have given me something else to wash down with my ginger ale (maybe vitamin C?). I do know that she made me feel loved and cared for, and that did wonders for my prognosis.
And without a doubt the chicken soup helped.
Rachel Johnson, EatingWell’s senior nutrition advisor, is dean of the University of Vermont College of Agriculture & Life Sciences.