Probiotics are the natural cultures or flora necessary to keep the digestive tract and immune system functioning properly. The normal human digestive tract contains about 400 types of probiotic bacteria that reduce the growth of harmful bacteria and promote a healthy digestive system. The largest group of probiotic bacteria in the intestine is lactic acid bacteria, of which Lactobacillus acidophilus, found in yogurt, is the best known. Yeast is also a probiotic substance. Probiotics are also available as dietary supplements.
It has been suggested that probiotics be used to treat problems in the stomach and intestines. Since a healthy digestive tract contains hundreds of different cultures, multi-strain probiotic supplements more closely match the natural ecology of the digestive system than probiotics with only one strain.

Every day, the good, natural flora in the body is killed off by stress, poor diet, caffeine, alcohol, antibiotics, antacids, over-the-counter and prescription medications, chlorinated water, and a toxic environment. Taking a multi-strain probiotic daily supports a healthy digestive tract and immune system by supporting the natural flora that is often destroyed by daily living.

Why should you take a daily dose of Probiotics? Acoeding to Harvard Women's Health Watch BOSTON, MA - reports that a growing body of scientific evidence suggests that you can treat and prevent some illnesses with supplements containing certain kinds of health-promoting bacteria, called probiotics (meaning "for life").

An estimated 100 trillion microorganisms inhabit every normal, healthy bowel, where they keep pathogens (harmful microorganisms) in check, aid digestion and nutrient absorption, and contribute to immune function. If these gut-dwelling bacteria become depleted—usually because of disease, stress, poor diet, or medications like antibiotics—health problems can result.

According to Harvard Women’s Health Watch, probiotic therapy has been best studied for the treatment of diarrhea. It may also help people with Crohn's disease, irritable bowel syndrome, and other gastrointestinal problems. Probiotics that help restore the balance of microflora in the vagina may be useful in treating such common female urogenital problems as bacterial vaginosis, yeast infection, and urinary tract infection. More study is needed to know which probiotic strains work best for which conditions.

Research has shown that certain probiotics may restore normal bowel function and may help reduce:

• Diarrhea that is a side effect of antibiotics.
• Certain types of infectious diarrhea.
• Inflammation of the ileal pouch (pouchitis) that may occur in people who have had surgery to remove the colon.
• These results suggest that eventually probiotics may also be used to:
• Help with other causes of diarrhea.
• Help prevent infections in the digestive tract.
• Help control immune response (inflammation), as in inflammatory bowel disease (IBD).
• Researchers are studying the use of probiotics for inflammatory bowel disease, colon cancer, and irritable bowel syndrome (IBS).

The recommended doses range by Harvard Women's Health from 1 billion to 10 billion colony-forming units (CFU)—the amount contained in a capsule or two_several days per week.
A daily supplement for one to two weeks may improve conditions such as infectious or antibiotic-related diarrhea.
The microorganisms in probiotic supplements need to be alive when you take them (or when they’re freeze-dried for capsules). They may die on exposure to heat, moisture, or air. Some require refrigeration.