By TARA PARKER-POPE

When the label tells you the food you are buying ��contains probiotics,�� are you getting health benefits or just marketing hype? Perhaps a bit of both.

Probiotics are live micro-organisms that work by restoring the balance of intestinal bacteria and raising resistance to harmful germs. They can promote digestive health and help shorten the duration of colds. But while there are thousands of different probiotics, only a handful have been proved effective in clinical trials.

There is no standard labeling requirement to help buyers make sense of probiotic products. The word ��probiotic�� on the label is not enough information to tell whether a given product will be effective for a particular health concern. Different probiotic species and strains confer different health benefits.

��It��s a huge problem for the consumer to try to make heads or tails of whether the products that are out there really work,�� said Dr. Shira Doron, an assistant professor of medicine at Tufts University in Massachusetts.

Consider Lactobacillus, a probiotic that comes in a number of strains, among them: Lactobacillus GG (often called LGG), which can be found in the diet supplement Culturelle as well as several milk products in Finland; L. casei DN114 001, included in Dannon products; and L. casei Shirota, found in Yakult, a popular probiotic drink from Japan.

Studies show that all of these strains are associated with reducing diarrhea; LGG has also shown a benefit in treating atopic eczema and milk allergy in infants and children, according to a 2008 report. Meanwhile, both LGG and Dannon��s L. casei strain have been shown in studies of children attending day care to reduce illness.

��Lactobacillus is just the bacterium,�� said Gregor Reid, director of the Canadian Research and Development Center for Probiotics. ��To say a product contains Lactobacillus is like saying you��re bringing George Clooney to a party. It may be the actor, or it may be an 85-year-old guy from Atlanta who just happens to be named George Clooney. With probiotics, there are strain-to-strain differences.��

After gathering at a Yale University workshop to review the available evidence, a panel of 12 experts concluded that there was strong evidence that several probiotic strains could reduce diarrhea, including that associated with antibiotic use. Several studies have also suggested that certain probiotics may be useful for irritable bowel syndrome, with the strongest recommendation for Bifidobacterium infantis 35624, the probiotic in the Procter & Gamble supplement Align. (Two members of the panel had ties to Procter & Gamble; three others had ties to other companies that sell probiotics.)

��The evidence for the general immune strengthening is just not there,�� said Barry R. Goldin, a Tufts professor who helped discover LGG but no longer receives royalties from the patent.

But the gastrointestinal tract is an important part of the immune system, and studies show that intestinal bacteria play an essential role in immune defenses.

Consumers interested in probiotics should look for products that list the specific strain on the label and offer readers easy access to scientific studies supporting the claims.


STUART BRADFORD