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These are some of the areas in which it’s claimed that probiotics can exact a beneficial influence. Others not listed here include optimizing intestinal transit time and hypertension (high blood pressure) relief.
Glamorous it isn’t, but prevention of diarrhea is the most frequently touted health claim for probiotics. While some doctors will now advise patients to take L. acidophilus when antibiotics are prescribed, as well as for some time after the antibiotics are discontinued, there isn’t much evidence that L. acidophilus is helpful here. There is more and better documented evidence for other probiotics, such as Lactobacillus rhamnosus GG, Lactobacillus reuteri and Saccharomyces boulardii. Because antibiotics can kill beneficial bacteria along with a pathogen, new pathogens have a chance to move in and colonize, potentially resulting in intestinal problems. This includes Clostridium difficile, a spore-forming bacterium that is the major cause of antibiotic associated diarrhea (AAD). Even mild cases of AAD are unpleasant; the most serious cases require hospitalization and can include arrhythmia, an alteration in heartbeat rhythm. Probiotics can provide mitigation or cessation of symptoms for some AAD sufferers, though not all.
There are instances, too, where probiotics have proven useful in cases of infant diarrhea. Infant diarrhea is always a matter for concern; small children can become dehydrated quickly from diarrhea as a result of their lower body weights, particularly if stricken by fever as well. Again, some trials have shown improvement in young children with acute or persistent diarrhea where probiotics were consumed, especially species of the lactobacillus family.
In cases of travelers’ diarrhea, it has not been ascertained whether probiotics can play a role in forestalling such an illness.
These are three terms for the same condition. Lactose intolerance occurs when the small intestine does not produce enough of the lactase enzyme to break down the sugar lactose present in milk and dairy products. When lactose remains undigested, it can cause bloating, stomach cramps, flatulence and diarrhea. The ability to digest lactose decreases naturally with time in many people; some 75% of adults are lactose intolerant to a degree. There is some belief that certain probiotics, including Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus bulgaricus, Streptococcus thermophilus and Streptococcus salivarius, allow for easier digestion of milk and other dairy products. Different probiotics may assist lactose digestion by various methods. However, it’s important to emphasize that not all studies agree that probiotics help with lactose intolerance. Photo of milk courtesy of the Midwest Milk Board.
It’s possible that probiotics can prevent colorectal cancer. Some studies suggest that probiotics can prevent cancer, but no two trials seem to agree on which microbes are most effective. Drs. Gorbach and Goldin, in a 1984 publication, maintained that Lactobacillus acidophilus reduces the concentration of three cancer-promoting enzymes in the intestinal tract. Some more recent material gives credit to certain members of the lactobacillus family, as well as Bifidobacterium. While there have been some promising results in trials, the reader must be cautioned that there are no definitive, large-scale, long-term studies linking any probiotic use to reduced risk of cancer, colorectal or otherwise. The lack of definitive scientific studies to date is due in part to the fact that cancer is “hard to study,” according to Dr. Mary Ellen Sanders. Dr. Sanders relates that some types of cancer have low incidences, and progression of the disease can be slow. Any legitimate cancer study involving probiotics, therefore, would require an enormous commitment, a large number of subjects, a great deal of money and a long period of time.
Immune System Enhancement
Can probiotics enhance or strengthen your immune system? Some 50% to 70% of the human immune system is based in the digestive tract. Specialized cells there operate as an initial barrier against some infectious agents. The immune system is exceptionally complex and can be affected by multiple factors, among them stress and age. There has been some evidence from clinical trials that probiotic cultures may stimulate particular components of the immune system, such as cellular and antibody functions. Animal and in vivo studies have demonstrated that some beneficial bacteria may increase the body’s ability to help itself when the immune system is under attack. There is also some research that suggests that probiotics may be able to lessen conditions brought on when the body’s immune system does not regulate itself in an ideal manner. But much more research is required before blanket generalizations about probiotics and the immune system can be accepted with confidence by consumers.
A 2003American Journal of Clinical Nutrition (78: 675-83) article on Danone’s “The Intelligent Intestine” symposium stated that, despite the abundance of literature on probiotics and immunity, “...a clear picture has not yet fully emerged because of the diversity of microorganisms and...because of the type of immune response studied (intestinal or systematic) in the body fluids or the cells—innate or acquired. The significance of the results varies widely.” In addition, the authors note that with fermented dairy products, different strains produce different effects, and the metabolites that are created by the fermentation process alone may also exert activity, which complicates research even further.
The article’s authors go on to discuss probiotics and their effects on healthy humans. It is known that children, especially infants, have both fewer strains of probiotics in their intestinal microflora, as well as a lesser number of these beneficial microbes overall. The authors note that this dearth results in infants being considered immunocompromised and more likely to develop gastrointestinal infections and food allergies. In adults, intestinal microflora populations are more stable than they are in children, but the quality of intestinal flora still exerts an effect. Right now, little is known about the influence lifestyle factors can exert as well, including stress, drug treatment or even changes in diet. To date, much of the research conducted has dealt only with antibiotics, not with healthy adults.
Asthma and Allergy Prevention
In 2006, in the largest study of its kind ever undertaken, researchers at the University of California at San Francisco launched a three-year study on 280 full-term, healthy babies with one asthmatic parent (parents with asthma are more likely to have children with asthma). During their first six months, half of the infants received a once-daily dose of active Lactobacillus GG and half received a placebo. The infants will have six follow-up visits. The results of this trial will not be known until at least 2009, and the sample size is quite small, but it’s another example of the widespread and varying conditions people hope that probiotics can positively affect.
If it seems that the incidence of asthma and allergies has increased dramatically in children in the U.S. for some years now, it isn’t just your imagination. The “hygiene hypothesis” postulates that environments with fewer microbes (homes with fewer siblings, fewer pets, more antiseptic living situations, fewer farm communities and heavier consumption of processed foods) are associated with greater incidence of allergies, asthma, eczema and the like. This theory holds that safe, controlled exposure to microbes for infants under the age of six months may allow the immune system to be more forgiving around potential allergens. And probiotics could have a place in such controlled exposure.
Color enhanced scanning electron
micrograph of the Lactobacillus
acidophilus by SciMAT/Photo Researchers, Inc., courtesy National Institutes of Health.
Reduction of Cholesterol Levels
A substantial percentage of the U.S. population has cholesterol levels that are considered “elevated,” that is, 200 mg/dL or higher. Technically referred to as “hypercholesterolemia,” an elevated cholesterol level can be a factor in the development of heart disease. While not the sole factor in determining serum cholesterol level, diet is known to play a role, although the degree to which this occurs varies by individual. It has been suggested that consumption of probiotics, especially those that are dairy food-based, may lower serum cholesterol, perhaps by causing a less efficient reabsorption of cholesterol in the intestinal tract. However, clinical evidence supporting this hypothesis is spotty.
Prevention of Infections
There is some evidence that Bifidobacteria are antagonistic toward certain pathogens, especially some strains of Salmonella, Staphylococcus, Shigella and Escherichia (particularly E. coli). The bifidobacteria, through several different mechanisms, may produce bacteriocins, peroxides, and lactic and acetic acid. These reduce the pH of the intestinal tract and provide an unfavorable environment for the growth of the pathogens.
Probiotics in the Lactobacillus genera are thought to be effective against Heliobacter pylori, which is a bacterium that colonizes the stomach and is associated with gastric ulcers and gastric cancer. Lactobacilli are also the dominant genera of bacteria in a healthy vagina; a lack of them is a risk factor for vaginosis. Once considered primarily a nuisance, vaginosis may be associated with many more serious conditions, including pregnancy and birth complications and pelvic inflammatory disease. Some studies have pointed to certain lactobacilli as effective in controlling the incidence of both Candida yeast infections and vaginal infections.
Scanning electron micrograph of the
Bifidobacterium bifidum by
SciMAT/Photo Researchers, Inc.,
courtesy National Institutes of Health.
Dr. Robert Martindale, a great proponent of probiotics who has been following research and news about them for over a decade, has seen studies where probiotics have topical applications as well. Probiotics can be applied to tracheostomies (temporary or permanent openings cut into the trachea, or windpipe), burns and skin to prevent infection.
Inflammatory Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS)
Ulcerative colitis and Crohn’s disease are two of the most widely-recognized inflammatory bowel diseases. Both can have serious consequences for those afflicted with them. It has been suggested that an exceptional sensitivity to normal intestinal microflora can trigger the initial inflammation. Some studies have been conducted during remission stages of these two diseases that showed that high intakes of particular probiotics could extend the remission period.
Irritable Bowel Syndrome (IBS) is a chronic condition causing abdominal pain, bloating, constipation and diarrhea. Estimates are that at least 10% to 15% of the American population has this condition; women are diagnosed with it far more often than are men. One hypothesis suggests that an important factor in IBS may be some type of imbalance in the intestinal microflora. Not enough clinical trials exploring the relationship between IBS and probiotics have been conducted to determine whether probiotics can have any substantial effect on this condition, but some relief from selected symptoms, especially pain, has been reported.