Kathleen Goldhar tried for years to figure out what was causing her young daughter to suffer from persistent, sometimes agonizing stomach pains.
Since age three, the now seven-year-old girl had complained of intense cramps that would stick around for a couple of nights, subside and then return days or weeks later, usually when she ate.
With little insight from doctors, at least one trip to the hospital with cramps that caused the little girl to writhe in pain, and myriad tests producing no answers, the single mom took the advice of a nutritional consultant who recommended probiotics.
Ms. Goldhar began adding a powdered supplement to her daughter's juice and within a couple of weeks noticed that her complaints diminished as the pain appeared to lessen.
"They seem to work," she said from Toronto. "It does seem to be a digestion issue and she seems to be able to sort of handle her food better. Her stomach doesn't hurt as much."
Ms. Goldhar is one of a growing number of people who have turned to the bacterial critters for a host of health reasons, including candida, digestion, diarrhea, boosting brain development and boosting the immune system.
Probiotics are live organisms, usually helpful bacteria similar to those found in the human gut, that can change or restore the intestinal flora. They are present in such foods as sauerkraut, miso and fermented products, but can also be taken in pill or powder form.
There are billions of bacteria in the body - on skin, in the mouth, the intestines and other body parts - that can maintain general health by raising resistance to harmful bacteria.
The World Health Organization defines probiotics as "live micro-organisms which when administered in adequate amounts confer a health benefit on the host."
The surge in popularity comes after manufacturers homed in on the category's potential benefits and began adding them to everything from yogurt, infant formula and juices to bread, chewing gum and chocolate. They can even be found in some floor cleaners and aftershaves.
Marketers have claimed the naturally occurring bacteria can shorten the duration of colds, prevent diarrhea, overcome allergies and even reduce the risk of certain cancers.
But health experts say the hoopla over probiotics has overshadowed actual scientific proof that they improve health, leading to confusion for consumers deluged with claims about products containing the micro-organisms.
Gregor Reid, who specializes in the study of probiotics, was on the panel that created the WHO's definition of probiotics and says many of the products claiming to contain them actually don't - because the specific bacteria haven't been proven in a human study to confer a health benefit.
"The majority of products on the market are not in fact probiotics," said Dr. Reid, a University of Western Ontario professor and head of the Canadian Research and Development Centre for Probiotics at the Lawson Health Research Institute in London, Ont.
"When you call something a probiotic, there should be an expectation that it's been clinically tested and shown to have a benefit, and unfortunately many products don't. So the first step is getting companies to do the studies."
The problem is that there are many different strains of friendly bacteria that perform many different functions. Most have not been proven to be effective in clinical trials.
For consumers, it's not clear on food labels how much and what type of bacteria a product contains, making it difficult to know if the probiotics are best suited for a particular health ailment.
Only some companies, like yogurt maker Dannon, list the specific bacteria that have been shown in trials to help with certain health issues, like regularity and digestion.
The company settled a $35-million lawsuit last year with customers dissatisfied over health claims it was making about yogurt products, leading to more explicit labelling.
Some experts say that shouldn't scare off consumers from using probiotics for conditions where there is some agreement on benefits, such as helping with some types of diarrhea, bowel regularity, colds and irritable bowel syndrome.
John Bienenstock, a professor of pathology and molecular medicine at McMaster University in Hamilton, said people have to look carefully at a particular product and determine exactly what it is.
"They have to look through the literature carefully, recognizing there is this problem of a lack of consistency of information and lack of consistency of products," said Dr. Bienenstock, who's also director of the Brain Body Institute.
"From a consumer point of view, it's very important that when you go out and see what's on the shelf, you know what's on the bottle and what it can do… There are health benefits and there is hype."
Regulatory agencies are trying to rein in the multi-billion-dollar industry, which saw consumer spending on probiotic supplements triple in the United States between 1994 and 2003.
The International Probiotics Association is planning a labelling scheme that would include a minimum bacterial count and an identification of the bacterial strain.
There is also a move afoot in Europe to control the claims with regulation that demands companies produce the scientific evidence to support their labelling.
Health Canada has developed a probiotics monograph, which includes detailed information on acceptable health claims, associated doses, source materials and required risk information.
It has also developed a guidance document that spells out when health claims can be made about food. The department website states that food products containing probiotics may have to remove the word if they're not accompanied by "specific, validated statements about the benefits or effects of the micro-organism."
Researchers say people need to scrutinize prebiotics just as closely. The sugar-type molecules are non-digestible foods that make their way through the digestive system and help good bacteria flourish. They are mostly found in carbohydrate fibres and can be taken in supplements or foods.
Dr. Reid said consumers have to research probiotic products themselves, using online sites like PubMed (www.ncbi.nlm. nih.gov/pubmed) to see what studies have been done to prove a company's claims.
He would like to see it made easier to know the strain of bacteria, its properties, what it does, how long it lasts if it's in powder form and where it goes in the body. Otherwise, he worries that skepticism over probiotics' actual benefits will sully ones that have been scientifically proven to work.
"There needs to be more clinical evidence or companies need to stop calling their products probiotics," he said.
"It shouldn't be a fad. I think the ones that are properly scientifically documented will be here to stay, but the other ones hopefully don't spoil it for everyone else."