Probiotic products whether from foods or supplements contain “friendly” microorganisms found as part of the normal flora in the human body. Probiotics are available in many forms such as yogurt and other cultured milk foods, capsules, tablets, beverages, and powders. Probiotics should not be confused with prebiotics, which are complex sugars (such as inulin and other fructo-oligosaccharides) that are ingested as fuel for bacteria already present in the gastrointestinal tract.
Many claims are made by probiotic supplement and yogurt manufacturers that these organisms help fight disease by boosting the immune system to protect against “bad bacteria” or benefit the gastrointestinal tract in various ways yet unknown. Just how are they holding up against scrutiny?
In a large analysis of 22 studies including more than 3000 patients, probiotics significantly reduced the chances of developing a type of diarrhea caused by a bacterium called Clostridium difficile. Clostridium difficile (klos-TRID-e-uhm dif-uh-SEEL), often called C. difficile or C. diff, can cause gastrointestinal symptoms ranging from diarrhea to life-threatening inflammation of the colon. Illness from C. difficile most commonly affects older adults in hospitals or in long-term care facilities and typically occurs after use of antibiotic medications.
Another large analysis of previous studies looked at 28 randomized controlled trials in about 3000 patients and found a significant preventive effect of problems associated with antibiotic use such as diarrhea by giving probiotics before or during the use of antibiotics.
Probiotics have been tested in people suffering from irritable bowel syndrome (IBS) but there are mixed results. In one large study with 300 patients, probiotic use did not produce improvement in symptoms; on the other hand, in another trial in Ireland, people with IBS saw improvements in bloating, an often reported symptom.
Probiotic use has been thought to help with inflammatory bowel diseases and in three separate studies, inflammatory markers called cytokines decreased in inflammatory bowel patients and in healthy volunteers.
No one has yet determined how probiotics benefit the gastrointestinal tract. A recent study found that they might alter the way food is metabolized or broken down.
In the first study, researchers used germ-free mice that were raised in an intestinal environment that mimicked humans, i.e. their guts were introduced to 15 human gut microbes. Germ-free animals are animals that have no bacteria, viral or parasitic agents living in or on it by being raised in isolation units. Germ-free animals are used in the study of probiotic research and other animal research requiring careful control of outside contaminants that can affect the experiment.
Next, seven sets of healthy, young-adult female twins were recruited. Both the “humanized” mice and the twins consumed a commercial probiotic-cultured yogurt for four months. Then, their gut compositions were examined before and after probiotic consumption.
The results? The bacterial species in the yogurt did not take up new residence in either the human or animal consumers. Thus the bacterial environment found in the guts of both mouse and man was roughly the same before and after yogurt consumption.
After that, the urine of the “humanized” mice was analyzed for metabolic changes. It was found that enzyme activity was significantly changed and that carbohydrate metabolism was most affected.
One co-author of the study, Dr. Jeffrey Gordon, a biologist and director for the Center for Genome Sciences at Washington University School of Medicine in St. Louis said: “adding a few billion of these microbial organisms to a gut community already containing tens of billions of bacteria can, in fact, influence the metabolism of food ingredients. The structure of the microbe community doesn’t change. But the function does”.
Properly labeled probiotic supplements will list the types of bacteria and/or yeast that are present. The genus name may also be abbreviated with its first letter (e.g., Lactobacillus acidophilus or L. acidophilus). It may be more effective to take a probiotic supplement with a mixture of strains instead of just one species. However, testing is often not done on these combinations and they may not work well together.
Most properly labeled supplements state the amounts of bacterial cells initially added at the point of manufacture. It is not uncommon for the amount of active ingredient in any supplement to decrease slightly over time. This is particularly true with living organisms in a probiotic product, so the “best by” date is probably most reliable. So make sure you notice the expiration date to ensure the highest number of living cells.
To gain probiotic benefits from yogurt or other dairy foods, look for products labeled “contains live cultures” or “active cultures.” Some yogurts will state the species of bacteria they contain.
Often some bacterial species will not be able to survive the stomach acid and therefore, will not be of any value. Some products coat their supplements with a protective substance to avoid this problem. In general, most Lactobacillus, Bifidobacterium, and Streptococcus species do not need any coating as they can survive passage through the stomach.
Concerns and Cautions:
There are no known safety issues with probiotic bacteria at appropriate doses in healthy people but some people occasionally notice a temporary increase in digestive gas. Since live bacteria are being consumed (even though they are “friendly”), people with a compromised immune system should be careful of these products and only consume them with the approval of their doctors. However, many experts are now recommending that people who have chronic infections with prolonged antibiotic use and the institutionalized elderly consider talking to their doctors about using a probiotic product.