The Value Of Probiotics

The World Health Organization defines probiotics as "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host." Your gut is normally colonized by more than 400 bacterial species, and, according to a 2000 "Current Issues in Intestinal Microbiology" review, each milliliter of stool in your colon contains one trillion organisms. Replenishing these organisms with orally-administered supplements is believed to alleviate a variety of conditions, including allergies, irritable bowel syndrome, inflammatory bowel diseases and infectious diarrhea, but probiotics are not approved for treating any of these conditions.

The Hygiene Hypothesis

The intestines of infants are devoid of bacteria at birth. Within days, a baby's gastrointestinal tract is colonized by bacteria acquired from its mother and its surroundings. "The Merck Manual of Diagnosis and Therapy" states that limited exposure to microbes in early life -- partly the result of smaller families and frequent use of antibiotics -- impairs the development of normal immune mechanisms that are protective in later years.

Allergies

A 2010 review in "Allergy and Asthma Proceedings" reports that the intestines of nonallergic children contain different microorganisms than those of allergic children. The author of this review suggests that administration of probiotics to infants and children could prove useful for preventing allergic diseases, especially allergic dermatitis. However, he cautions that the most effective bacterial strains for such a practice have not been identified, so no recommendations can be made regarding the use of probiotics for preventing or treating allergies.

Diarrhea

Probiotics have been shown to alleviate diarrhea caused by viruses, such as rotavirus and antibiotics. According to the "American Journal of Health-System Pharmacy," probiotics are believed to exert their beneficial effects by increasing intestinal acidity, preventing invasion by infectious organisms and modifying the immune response within the gut. However, the benefits exerted by one strain may not apply to another, so specific recommendations must be based on each patient's situation.

Irritable Bowel Syndrome

Although the exact cause of irritable bowel syndrome, or IBS, is unknown, there is some evidence that alterations in the composition of gut microorganisms and inflammation of the intestinal wall play a role. One 2009 study in "The American Journal of Gastroenterology" demonstrated that a specific strain of probiotic -- Bifidobacterium infantis -- alleviated the symptoms of IBS sufferers. The effectiveness of other probiotic strains is unknown, so the widespread use of probiotics for IBS cannot be advised.

Considerations and Precautions

There is good evidence that probiotics are of some value for treating or preventing specific conditions, such as infectious diarrhea, antibiotic-associated diarrhea or allergic dermatitis. Whether they are useful for other conditions, or whether they offer benefits to otherwise healthy individuals, remains to be demonstrated. The safety of probiotics for certain populations, such as immunocompromised patients, is untested. If you think probiotics might be beneficial for you, speak with your physician.