The power of probiotics: learn why these friendly bugs are vital for immunity and more.(SUPPLEMENTS: SHOP SMART)

THE BASICS: Your digestive tract contains more than 500 different types of bacteria and an estimated 100 trillion individual bacteria, most of which are beneficial. In fact, you have 10 times more bacteria in your gastrointestinal tract than you have cells in your entire body. Probiotic supplements contain some of these bacterial species and can provide many health benefits.

ALIAS: The term probiotics is a general one. The names of specific intestinal bacteria can be confusing because there are so many different types. For example, lactobacillus refers to a genus of bacteria that consists of many species, including L. acidophilus, L. rhamnosus, and L. casei. Some species, such as L. casei, have subspecies, such as L. casei GG. There's more--all bacteria have two names, such as Bifidobacteria bifidum; the first represents the genus, and the second identifies the species. The names are usually abbreviated, such as B. bifidum.

HOW PROBIOTICS WORK: Intestinal bacteria contribute to our health in numerous ways, and probiotic supplements support these functions. They help us digest food and also make small amounts of some vitamins. They protect against infectious bacteria, in large part by crowding them out. Intestinal bacteria secrete peptides (protein-like substances) that help maintain our immune activity and defenses against a wide range of threats.

HEALTH BENEFITS: Probiotics have many different health benefits.

* Antibiotic-related diarrhea. At one time or another, nearly everyone takes antibiotic drugs to fight bacterial infections. However, antibiotics kill both pathogens and friendly intestinal bacteria. The consequence is what doctors call a "microbial vacuum," which is sometimes filled by opportunistic disease-causing bacteria, such as Clostridium difficile. C. dill, as it is commonly known, can lead to a secondary infection and diarrhea.

Probiotic supplements are essential for fighting C. diffand restoring normal gut health. Start taking probiotics with antibiotics--the probiotics will not interfere with antibiotics, but they will lessen their undesirable effects. It's important to continue taking probiotic supplements for at least a month after stopping antibiotics. The reason is that the "dysbiosis" caused by antibiotics can linger for years and set the stage for local and systemic candida yeast infections. Consider a probiotic supplement containing L. casei GG, B. lactis, or S. thermophilus.

* Infectious diarrhea. So-called stomach flus and cases of food poisoning are often caused by infectious bacteria. Probiotics can help in infants, children, and adults because these good bacteria secrete their own types of antibiotics, which fight infection-causing germs. In an analysis of nine studies, Cornelius W. Van Niel, MD, of the Hniversity of Washington, Seattle, found that treatments with lactobacillus probiotics led to faster recovery from gastrointestinal tract infections.