Probiotics

Overview

“Probiotics” is a term used to refer to a group of “beneficial” bacteria that help maintain the health and function of the gastrointestinal tract. Probiotics have been defined as viable microorganisms that (when ingested) have a beneficial effect in the prevention and treatment of specific pathologic conditions. These microorganisms are believed to exert biological effects through a phenomenon known as colonization resistance, whereby the indigenous anaerobic flora limits the concentration of potentially pathogenic (mostly aerobic) flora in the digestive tract. Other modes of action, such as supplying enzymes or influencing enzyme activity in the gastrointestinal tract, may also account for some of the other physiologic effects that have been attributed to probiotics.

Acidophilus (Lactobacillus acidophilus) and Bifidus (Bifidobacterium lactis) of varying strains are popular forms of “good” bacteria found in dietary supplements. By displacing other bacteria and yeast, Acidophilus and other lactic acid bacteria may also play an important role in immune system function and prevention of gastrointestinal problems, including cancer. A wide variety of beneficial bacterial strains can be found in cultured yogurts and in freeze-dried form as dietary supplements. Claims for these products are generally made to reduce cholesterol levels (marginal evidence), support immune system function (solid evidence), maintain a healthy digestive system (solid evidence), and prevent colon cancer (preliminary evidence).

Comments

Dietary supplements providing Acidophilus in combination with some of the other beneficial probiotic bacteria are fairly inexpensive. Given the strong evidence for their beneficial effects on immune system function and the possibility that regular consumption may reduce colon cancer risk, these supplements would be a good choice for anybody looking for a general immune system booster.

Scientific Support

The digestive system is home to millions of bacteria that help digest, modify and convert the food we eat. Any alteration in the gastrointestinal environment is likely to influence the activity of these beneficial bacteria – sometimes posing health problems. Maintaining the “normal” populations of these good bacteria in the intestines, through consuming them as supplements or in cultured yogurt, can help displace disease-promoting bacteria and yeast that may gain a foothold when the levels of good bacteria drop.

Acidophilus and other beneficial bacteria are both acid- and bile-resistant, and thus capable of surviving transit through the gastrointestinal tract after they are ingested. These bacteria are sometimes called “probiotics” because regular consumption is linked to health benefits such as reducing cholesterol, preventing microbial growth, modulation of the immune system and, possibly, prevention of colon cancer.

Both human and animal studies have shown direct benefits of regular consumption of acidophilus and other beneficial bacteria on immune system function (Arunachalam et al. 2000, Gill et al. 2000 and 2001, Shieh et al. 2001). Overall, the probiotic bacteria tend to result in an enhanced ability of the immune system to recognize and destroy invading organisms. Several key components of the immune system, including macrophages, immunoglobulins and cytokines are altered by regular intake of beneficial bacteria. Populations of white blood cells are known to increase in number and activity following 1-2 weeks of consuming beneficial bacteria (Gill et al. 2001, Shieh et al. 2001). Importantly, resistance to viral and bacterial infections is significantly improved following regular intake of probiotics.

Epidemiological studies support the possibility that consumption of beneficial bacteria (from fermented milk and yogurt) may play a role in the prevention of colon cancer and inflammatory conditions (Gill et al. 2000 and 2001, Isolauri et al. 2000, Shieh et al. 2001). Test tube studies have shown that Acidophilus can decrease the cancer-causing potential (mutagenic activity) of various carcinogens – possible due to a direct interaction between the carcinogens and the bacteria. Consumption of acidophilus (and other lactic acid bacteria) has also been shown to reduce levels of cancer-causing enzymes in the digestive tract, supporting the possibility that probiotics do indeed play a role in the prevention of colon cancer.

Safety/Dosage

There are no safety issues associated with regular consumption of Acidophilus or other probiotic bacteria at recommended levels, although those individuals with severe gastrointestinal ailments (Crohn’s disease or ulcerative colitis) should consult with their personal physician prior to consuming probiotic supplements. Most probiotic products will typically list the type of bacteria and the number of “live cells” on the label or side panel. There are no strict guidelines for dosage intake, but 1-10 billion CFUs (colony forming units) is a general rule of thumb and corresponds to effective levels used in human studies.

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EDITOR'S NOTE: This monograph can be found in The Health Professional's Guide to Dietary Supplements (Lippincott, Williams & Wilkins) by Shawn M. Talbott, PhD and Kerry Hughes, MS.