It pays to befriend bacteria - the good kind, that is.
Probiotics are friendly microbes that may strengthen the immune system by crowding out bad germs that make us sick. A German study found that healthy men and women who took probiotics daily for three months shortened bouts of the common cold by almost two days and reported reduced severity of symptoms, such as headaches, coughing, and sneezing.
Aim for three servings a day of probiotic-rich foods--yogurt with live bacteria, aged cheese, kefir, or other fermented foods (like sauerkraut or kimchi), says Dr. Gary Huffnagle, a professor of internal medicine at the University of Michigan Medical School and author of "The Probiotics Revolution."
If you prefer a supplement, Huffnagle recommends choosing one with 3 billion to 5 billion CFU (colony-forming units).
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