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Research Update

Beneficial Bacteria

BENEFICIAL BACTERIA PROMOTE HEALTH LOCALLY AND SYSTEMICALLY

Gastrointestinal bacteria are not independent and isolated from their human host. Rather, they interact intricately and intimately with that host. The health and makeup of the bacterial population depends on the health of the host, and the health of the host in turn depends on the metabolic activities of the bacteria. Thus, metabolic reactions occurring in the gut can have consequences both locally - for example, on the intestinal mucosa - or systemically.

Local effects. A thriving population of lactic acid - producing bacteria (so-called "good" bacteria because they perform beneficial metabolic activities) often goes unnoticed. In contrast, the local effects of so-called "bad" bacteria in the gut can be dramatic, manifested as diarrhea and in severe cases, colitis (inflammation of the colon). Animal studies indicate that beneficial bacteria may play a role in preventing cancer, especially colon cancer.

Systemic effects. Gastrointestinal bacteria can generate both beneficial byproducts (e.g., vitamins, enzymes, lactic acid, antibiotics, proteins) and detrimental ones (toxins, carcinogens). These byproducts can affect the central nervous system, blood vessels, and perhaps even tumor formation in various organs.

The byproducts produced depend on the types of bacteria colonizing the gut. The human gastrointestinal tract is home to more than 400 species of bacteria. A thriving population of beneficial bacteria can suppress the growth of pathogens. Lactic acid - producing bacteria play an important role in maintaining a healthful balance of intestinal flora and especially in limiting the growth of undesirable pathogenic bacteria.

CANCER, ESPECIALLY COLON CANCER

More than 20 years of research have demonstrated that beneficial bacteria are capable of suppressing tumor growth through a variety of mechanisms, such as: metabolic conversion/degradation/absorption of carcinogenic compounds reduction in the level of fecal bacterial enzymes stimulation of the immune system The evidence for cancer inhibition is not extensive; research indicates that certain types of bacteria and cultured dairy products may play some protective role. For instance, many beneficial bacteria produce lactate, which lowers the pH of the colon. Low colonic pH inhibits the growth of pathogens and is associated with intestinal health. Alternatively, beneficial bacteria may compete with pathogenic bacteria for resources, resulting in lowered amounts of pathogen-produced toxic metabolites. In one study, for instance, rats that consumed an acidophilus supplement excreted fewer cancer-causing substances than those not receiving the supplement.

Animal studies. Cultured dairy products or starter cultures used by the dairy industry can inhibit chemically-induced colon tumors and transplanted tumors in rodents.

Beneficial bacteria may delay the onset of cancer. In one set of experiments, chemically-treated animals were given either powdered Lactobacillus acidophilus or a placebo. At 20 weeks, only 40% of the animals who had received the acidophilus supplement had colon tumors, compared to 77% of the control animals. By 36 weeks, however, 73% of the acidophilus-treated animals and 83% of the controls had colon tumors. The authors concluded that the addition of this type of Lactobacillus to the diet can delay the formation of colon tumors.

Lactobacilli may impede the spread of cancer as well. Two studies looked at the ability of yogurt to inhibit the proliferation of tumor cells in mice and found that yogurt consumption resulted in a 28-35% reduction in the number of tumors when compared to control groups fed milk. Another study showed a 16-41% reduction of tumor proliferation in acidophilus-fed animals. Another group of researchers observed that Lactobacillus bulgaricus possesses potent antitumor activity Tumor-ridden rats experienced marked reduction of tumor growth and size (at least 20%) after infusion with extracts from Lactobacilli. Animals in the test group lived twice as long as those in the control group.

Cancer inhibition has been observed in animals pretreated with Lactobacillus acidophilus and Lactobacillus casei. In mice fed acidophilus-fermented breast milk, the growth of experimentally induced tumors was inhibited, but only in animals who were administered the bacteria before the onset of tumor growth. Similarly, Lactobacillus casei inhibited tumor growth in mice. Again, the antitumor effect was only seen in pretreated animals.

HUMAN STUDIES

Certain pathogenic bacteria are able to produce enzymes which can convert harmless substances in the intestine into cancer-causing compounds. Studies in which volunteers consumed large amounts of acidified milk every day showed that as the intestinal content of lactic acid bacteria rises, the concentration of certain detrimental enzymes falls.

INTESTINAL INFECTIONS CAUSING DIARRHEA, COLITIS (INFLAMED COLON), AND CONSTIPATION

Lactobacilli may also be useful in helping treat gastrointestinal infections, particularly those causing diarrhea and, in severe cases, colitis (inflamed colon). In developing nations, diarrhea is a major risk for travelers. Lactobacilli casei may be especially effective in protecting the intestines against bacterial infections.

LACTOBACILLI HELPS DECREASE ANTIBIOTIC-INDUCED DIARRHEA AND COLITIS

Diarrhea can be a common side effect of treatment with antibiotics, which kill good as well as bad bacteria. Gotz and colleagues observed a reduction in the rate of antibiotic- induced diarrhea from 14% to 0% in patients given a Lactobacillus preparation. In people treated with antibiotics, beneficial intestinal flora recolonized faster in groups receiving Lactobacilli than in those receiving a placebo. In addition, fewer antibiotic- resistant strains were seen in groups receiving Lactobacilli compared to those receiving a placebo. Similarly, animal studies indicate that beneficial bacteria may protect against sometimes deadly infections, such as those causing fatal antibiotic-associated colitis.

LACTOBACILLI MAY HELP PROTECT TRAVELERS

Two independent, double-blind controlled experiments carried out in Egypt showed that a capsule product containing Lactobacillus acidophilus, Bifidobacterium bifidum, Streptococcus thermophilus, and Lactobacillus bulgaricus consumed at every meal conferred significant protection against travelers' diarrhea. The placebo group suffered 50% more cases.

LACTOBACILLI MAY HELP PROTECT INFANTS AND CHILDREN FROM INTESTINAL INFECTIONS

Lactic acid bacteria are already established in the intestines of newborn babies and are critical to their health, helping children resist diarrhea-causing bacterial infections. Zychowicz and colleagues treated 31 Polish children with salmonelli- or shingella induced diarrhea with acidophilus milk. After drinking the fermented milk, symptoms disappeared in 43% of the children with a salmonella infection and 67% of those with shingella. Continued consumption of acidophilus milk resulted in elimination of diarrhea in all the children. In another study, Niv and colleagues used yogurt to treat infants with diarrhea. Yogurt-fed infants had a 50% shorter duration of diarrhea compared to a group treated with antibiotics alone.

CONSTIPATION

Studies also indicate probiotics may help alleviate constipation.

IMMUNITY AND RESISTANCE TO DISEASE

Beneficial bacteria are capable of boosting immunity and increasing resistance to disease. Evidence for this protective role was obtained largely from studies of experimental animals that either had inadequate gut microflora or had been treated with antibiotics. Both types of animals are much more susceptible to infections than animals with intact gut flora. When disease resistance is low, the content of lactic acid bacteria in the feces is considerably reduced. Insufficient gut flora makes it easier for pathogens to cause disease and death. This fact was dramatically demonstrated in an experiment in which only 10 cells of pathogenic bacteria (Salmonella) were necessary to kill a guinea pig with inadequate gut microflora; about a trillion cells were required to kill an animal with complete microflora!

Good bacteria, on the other hand, colonize the gut and render it difficult for pathogenic bacteria to establish residence. It is well known that resident microorganisms can prevent the implantation of invaders. In essence, beneficial bacteria enjoy a sort of "home court advantage," as they stick to the intestinal wall better than pathogenic bacteria, and the ability to colonize the gut depends on the ability to associate with the intestinal wall.Beneficial intestinal flora help protect the gut against colonization by pathogens including Clostridium difficile, Clostridium botulinum, F coli, Salmonella, Shigella, Pseudomonas, and Candida albicans.

Beneficial bacteria may also boost the immune defenses of the host. Lactobacillus casei, for instance, can stimulate natural killer cells, whose main job is destroying tumor cells. Lactobacillus acidophilus, Lactobacillus helveticus, and Bifidobacterium longum also enhance the immune response.

INDIGESTION RESULTING FROM INSUFFICIENT LACTASE

In some individuals, cells in the wall of the small intestine fail to make lactase, the enzyme which digests lactose (milk sugar). The resulting condition, lactose intolerance, is characterized by diarrhea, gas, bloating, and abdominal cramps following the consumption of milk and other dairy products.

Gastrointestinal symptoms appearing after the consumption of lactose by lactase deficient individuals do not seem to occur after ingestion of yogurt and other fermented milks. Lactobacilli use lactose in their production of lactic acid, so fermented milks have less lactose than nonfermented milks. Additionally, Lactobacilli are capable of producing enzymes responsible for the breakdown of lactose.

NUTRITIONAL STATUS

Lactobacilli improve a host organisms ability to utilize food. Numerous animal studies have shown that, compared to animals that were fed unfermented dairy products, those fed Lactobacillus-fermented products, such as yogurt, kefir, fermented milk, and cultured buttermilk, grew more and better utilize the nutrients in their food.

Acidified milk products are of greater value to the body than ordinary milk. Cultured dairy products have higher levels of specific vitamins and minerals, as well as proteins and carbohydrates in a more digestible form. For instance, Lactobacilli produce B- vitamins and enzymes that contribute to the breakdown of protein, fat, and lactose. In addition, bioavailability of calcium, zinc, iron, manganese, copper, and phosphorus is higher in yogurt than milk.

Research Update References: (available upon request)