Some people avoid dairy products when they’re sick because they are thought to further increase mucus secretions, but scientific evidence has yet to support this. 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.
So go ahead and have that glass of milk or a latte—the vitamin D in it may help boost your immune system. In a study of more than 300 Japanese children, those who took daily vitamin D supplements (1,200 IU) were 40 percent less likely to get a common flu virus than kids who took a placebo. Studies indicate that the nutrient may help immune cells identify and destroy bacteria and viruses that make us sick, says Adit Ginde, M.D., M.P.H., a public health researcher at the University of Colorado School of Medicine in Denver. Because a cup of milk delivers about 115 IU of vitamin D, and other food sources (oily fish, such as salmon or sardines) also only deliver small amounts, you may need to consider a supplement.
Don’t skimp on yogurt, either—it contains good-for-you probiotics that may actually stimulate your immune system.