As yogurt ads shift from hearty centenarian Soviet peasants to Hollywood stars with tummy troubles, so has the publics and sciences notion of probiotic cultures.

WHOs your favorite bug

The World Health Organization (WHO) defines probiotics as microorganisms that, when administered in adequate amounts, confer a health benefit on the host (ftp.fao.org/es/esn/food/wgreport2.pdf, 2002). Many of these involve one of the bugs preferred homes, the human digestive tract.

The large intestines natural beneficial microbial flora help digest food components not previously digested in the small intestine, such as digestion-resist fibers, plus produce substances with other beneficial effects, such as short-chain fatty acids that can suppress bad bugs and the production of carcinogenic compounds. Research indicates probiotics might be useful in addressing a range of digestive problems, such as constipation, diarrhea, Helicobacter pylori (the microorganism linked to ulcers), irritable bowel syndrome, inflammatory bowel disease and lactose intolerance.

Studies strongly suggest that probiotics are effective in treating and possibly preventing diarrhea caused by antibiotics or certain infections, such as those caused by rotavirus, particularly strains of Lactobacillus and Saccharomyces boulardii. WHO suggests probiotics potentially provide an important means to reduce problems caused by infectious diarrhea, which is responsible for several million deaths globally each year.

Digestive disease fighters

In a 2008 presentation on Probiotics and Inflammatory Bowel Disease, for the American College of Nutrition 49th Annual meeting, Dr. Stefano Guandalini, professor of Pediatrics, University of Chicago, Comer Childrens Hospital, Chicago, suggests that probiotics would be helpful for those suffering from maladies such as Crohns disease and ulcerative colitis for several reasons: Essentially probiotics are known to interfere with bacterial pathogens by reducing their bonding to the enteral sites, producing antibacterial substances and even competing for receptor sites. They also enhance innate immunity by decreasing the production of inflammatory cytokines and increasing the production of anti-inflammatory cytokines. They finally improve the intestinal health by increasing the barrier integrity and survival.

Guandalini went on to say that these proposed mechanisms supported the theory that probiotics have a role in balancing inflammation in these diseases, which is supported by research in animal models. Research in humans indicates additional studies are needed to support the hypotheses that probiotics (Lactobaccillus, in particular) might induce and maintain remission of Crohns disease and ulcerative colitis, however. The current, limited body of human research has not found probiotic consumption results in significant improvement in Crohns disease, but it has found a more-positive correlation in helping ulcerative colitis, particularly in children, and a positive effect on a condition called pouchitis, an inflammatory complication in patients that have had colon-removal surgery.

Using the good guys

Different strains of the same species can have markedly different effects, according to another presentation at the American College of Nutrition meeting, The Potential Uses of Probiotics in Human Health, by Mary Ellen Sanders, Ph.D., consultant, Dairy and Food Culture Technologies, Centennial, CO. She notes that clinical support to substantiate claims must be obtained for each strain or blend, which makes it very difficult in terms of communications on probiotics, because its so much easier to talk in generalities than to talk about specifics.

Most experts recommend daily dosage levels ranging from 5 to 20 billion CFUs of the live cultures to achieve benefits.  However, its not possible to come up with a single number as a minimum dose for probiotics, according to Sanders. Sometimes Ive seen the number one billion kicked around109 live cells is a minimum dose for probiotics. But, in fact, what I would argue is thats a very scientifically unsubstantiated statement, because the products, strains levels and clinical endpoints differ. She strongly recommends the levels used in products should be based on levels found to be efficacious in human studies for a particular effect.

WHO has issued a comprehensive paper on the Guidelines for the Evaluation of Probiotics in Food.