As much as we seem to be engaged in a constant battle with bacteria - washing our hands, pasteurizing our food, getting vaccinated - not all of these creatures are bad. These "good bacteria" are vital to the development of the immune system, in fighting disease-causing microorganisms, and to digesting food and absorbing nutrients.
Our bodies are a complicated ecosystem full of flora. In fact, the bacteria outnumber our own cells by 10 times. There are around 10 trillion cells that make up the human body, and we have around 100 trillion bacteria cells in our digestive tracts.
As more people become increasingly aware of the importance of this "good bacteria," hundreds of products in recent years have attempted to catch our eye by promising to help our troubled stomachs. Probiotics, defined as "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host," have become a big business. During a casual flip through the television channels, I frequently encounter commercials filled with attractive women gushing that their digestion has never been more regular thanks to certain yogurts or other products.
There may be something to some of those claims.
Probiotics include both yeastlike members of the saccharomyces group and teria, which usually come from two groups: Lactobacillus or Bifidobacterium. Probiotics are sold as capsules, tablets and powders, as well as in a growing number of foods. Among them, yogurt, yogurt drinks, kefir, miso, tempeh, as well as some juices and soy beverages. Sometimes the bacteria were present originally, and sometimes they are added during the preparation of the foods.
In our own bodies, we each have a mix of bacteria, and that combination can vary from person to person. Maintaining the right balance of bacteria is important to our health. This balance may be thrown off by antibiotics, which may be necessary to destroy an infection but may kill friendly bacteria in the process. Or, it may be thrown off due to "unfriendly" microorganisms, such as disease-causing bacteria, yeast or viruses.
There is reasonable evidence that probiotics are effective in treating - and in some cases, potentially preventing - diarrhea caused by antibiotics, traveler's diarrhea and certain kinds of infectious diarrhea. Several strains of lactobacillus and Saccharomyces boulardii have been shown in studies to be effective for this purpose. A study in the British Medical Journal used DanActive, which contains lactobacillus and several other bacteria, and found some evidence that participants who drank it twice daily before starting and while taking antibiotics were less likely to develop diarrhea than those drinking milkshakes with no bacteria. There is some evidence that some probiotics may decrease lactose intolerance and improve some forms of inflammatory bowel disease. Other claims such as help in fighting cancer, improving oral health, decreasing eczema or other allergies, or preventing urinary tract infections or vaginal infections in women require much more research, as the data supporting these salutatory effects is weak. Also, there is a large placebo effect in these studies, as there is in most studies dealing with complementary or alternative medical therapies.
Even in cases where probiotics have been shown to be effective, it is only using specific strains of bacteria in specific amounts. Not just any probiotic will do. Also be aware that the U.S. Food and Drug Administration has not approved any specific health claims for probiotics, and the FDA considers these as food products and not drugs. Product labels cannot legally declare that the probiotic can cure, treat, or prevent disease. That doesn't stop products from making a host of vague health claims.
To get the most out of the probiotic products crowding the shelves of your local grocer, arm yourself with information. First, know that it's only a probiotic if there's been a scientific study that shows that it "confers a health benefit on the host." There are thousands of different bacterial strains, and only a handful have been tested for health promotion. Further, while there is some evidence that probiotics may be helpful in treating some illness, it's unknown whether healthy people receive any benefits.
Next, note what strain of bacteria is used in the product. Don't expect all strains to have a convenient, and somewhat easy-to-remember name like Bifidus Regularis, or as it's known in the United Kingdom, Bifidus Digestivum. Those names, incidentally, are marketing monikers that roll off the tongue more elegantly than this bacteria's scientific name: Bifidobacterium lactis DN 173 010. But to understand what you're getting in probiotics, you need to know the genus (as in Bifidobacterium), the species (as in animalis) and the strain (a series of numbers, in this case DN 173 010). Look for products that give the specific names of the strains they use - then you have a chance to determine if the bacteria in the product is one that has been used in scientific studies and shown to be effective.
You will also want to note how much of the probiotic each serving of the product contains. It's also worth checking the websites of the company selling the product, where you may learn about the research that suggested there was a health benefit from the probiotic, and how much of it was used in the research.
Keep an eye on the dates on the product. Organisms can die off while the product is sitting on the shelf. Also look for yogurts that are labeled as containing "live and active cultures." Those that are merely "made with active cultures" may have been heat-treated after fermentation, which kills the bacteria. "Live, active cultures" are not necessarily probiotics - meaning that they haven't been tested for health benefits.
Their use has not been extensively studied in children or the elderly, and their safety in individuals with compromised immune systems has not been established. Lastly, while no studies have found adverse effects from probiotics more serious than gas or bloating, don't start using them as a medical treatment without consulting your health care provider, as there may be better, more established treatments available for your medical problem.