Harvard Health Letter

What you should know about: Probiotics

When you consider ways to stay healthy as cold and flu season approaches, consuming live bacteria may not be at the top of your list. But not all bacteria are bad for you. In fact, "good" bacteria found in food and dietary supplements may help you ward off illness this winter and throughout the year. The supplements are called probiotics. "Probiotics have been shown to secrete protective substances which turn on the immune system and prevent pathogens from taking hold and creating major disease," says Dr. Allan Walker, director of the Division of Nutrition at Harvard Medical School and a world-renowned expert in the probiotics field.

The bacteria balance

Your lower gastrointestinal tract is home to 100 trillion microbes, most of which help digest food, fight harmful bacteria, and regulate your immune system. Such helpful microbes are "good bacteria." An imbalance of the good and bad bugs in your gut can make you sick. For example, germ-killing antibiotics may disrupt the balance, leading to diseases that cause diarrhea. Imbalances may also lead to certain autoimmune diseases and allergies.

Probiotics to the rescue

You can help restore the bacteria balance by beefing up your inventory of good bugs with probiotics. They are live colonies of good bacteria found in dietary supplements and in foods. The most commonly used species (among a potential 3,000 or so) are in the Lactobacillus and the Bifidobacterium families. These are routinely used to treat a variety of gastrointestinal conditions, vaginal and urinary tract infections, and oral health problems. Dr. Walker says there's also evidence that probiotics as a supplement can reduce the number of colds you'll have in a year.

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