Whoever first advised people to feed a cold probably did it for the wrong reasons. Colds aren't the result of being chilled, and eating raises body temperature only slightly for only about 20 to 30 minutes (which is why experts advise you to wait that long before sticking a thermometer under your tongue). But that anonymous sage got the most important thing right: Eating well is an important part of nursing a cold.
Research shows that your immune system needs to be properly nourished to function properly, and that's especially important when you're run down. In the mid-1990s, for example, the U.S. Army noticed that Ranger trainees were succumbing to infections during training [source: McBride]. Government researchers discovered the problem wasn't the stress of hard exercise, but rather an inadequate diet. When male soldiers didn't consume enough calories to meet their daily needs, their T cells' ability to attack invading microbes decreased by as much as 60 percent [source: McBride].
Studies on animals also indicate that being undernourished makes it tougher to fight off an infection. In a study published in 2008, for example, Michigan State University nutritional immunology researcher Elizabeth Gardner found that mice with a calorie-restricted diet were more likely to die during the first few days of infection than mice with a normal diet, and they took longer to recover from the illness [source: MSU News].
Conversely, a 2002 study by Dutch researchers found that eating actually stimulates the type of immune response that destroys the viruses that cause colds. Six hours after a meal, human subjects' levels of gamma interferon, a substance involved in the process by which T cells destroy cells invaded by pathogen, more than quadrupled. In contrast, a group who drank only water saw their gamma interferon levels drop slightly [source: van den Brink].
But just stuffing your face with fast food or whatever happens to be in your refrigerator isn't necessarily a good idea, either. What are the best menu items for cold sufferers?