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by Richard N. Podell, M.D.
"Doctor, how can I strengthen my immune system?"
As a practicing physician and nutritionist, I hear that question at least three times a day. The good news is we can strengthen the immune system's resistance to infection by taking supplements of Lactobacillus acidophilus or Bifidobacterium bifidum, two breeds of "friendly" bacteria that normally live in the human gastrointestinal (G.I.) tract.
Lactobacillus attaches itself mainly in the upper G.I. tract (small intestine); bifidobacterium resides mainly in the lower G.I. tract (large intestine). Research shows that these friendly bacteria strengthen the ability of the immune cells surrounding the G.I. tract to defend the body against toxins, bacteria and allergens. It is thought that the G.I. tract's immune cells, a type of lymphocyte, in turn signal immune cells elsewhere in the body to increase or decrease activity.
Researchers from the departments of immunology and biochemistry at the University of Paris tested the effect of oral supplements of friendly bacteria on the ability of white blood cells to attack and destroy hostile microorganisms.
In one study, 28 healthy adult human volunteers took one of three fermented milk supplements: those with no friendly bacteria added, those with L. acidophilus or those with B. bifidum. The supplementation amounted to a daily dose of 70 billion colony-forming units (cfu) of L. acidophilus or 10 billion cfu of B. bifidum.
Scientists examined volunteers' blood samples after three weeks and checked the phagocytic activity of each person's white blood cells by gauging the cells' ability to attack and ingest E. Coli, a bacteria with moderately high potential for causing disease.
The percentage of white blood cells that were able to attack and "eat up" E. Coli doubled in volunteers taking either L. acidophilus or B. bifidum--an increase from 40 percent to 80 percent. Even better, six weeks after stopping the bacteria supplements phagocytic activity was still much higher than at the start of the study, although it had fallen off from its peak during supplementation. With fermented milk alone there was no increase in phagocytic ability.
The native bacteria living within the G.I. tract play an important role in protecting us from intestinal infections caused by "unfriendly" gut organisms such as candida (Candida albicans) or the diarrhea-causing bacteria Clostridium difficile. This may be caused by crowding the undesirable organisms out of their potential biological niche.
Whole Body Protection
The current study breaks new ground because it shows that lactobacillus and bifidobacterium supplements caused sustained immunological protection--both stimulated immune cells that were outside the G.I. tract, i.e. white cells in the blood.
Bacteria-containing supplements, called probiotics, are only one of many natural substances being studied for their ability to improve our overall resistance to infection. Vitamins C and A, selenium, zinc, echinacea (Echinacea angustifolia or purpurea), aloe (Aloe vera), garlic (Allium sativum), silymarin (from milk thistle, Silybum marianum) and cow's milk whey also improve the body's natural resistance to infection. Probiotics are especially intriguing because of growing evidence that connects bacterial action within the G.I. tract to a number of body processes.
It is estimated there are more bacteria in the gut than cells in the body or stars in the sky. In addition to their immune system effects, gut bacteria manufacture vitamins, detoxify environmental chemicals and metabolize hormones and other substances. Unfriendly organisms in the G.I. tract, however, not only can cause infections, but can produce toxic products including a host of carcinogens.
Beta glucuronidase, for example, is an enzyme produced by certain unfriendly gut bacteria. High levels of beta glucuronidase disrupt the body's ability to detoxify both natural hormones and environmental chemicals. People who have high levels of beta glucuronidase in their stool may be at increased risk for breast and colon cancer. Because beta glucuronidase in the stool is easily measured, it may help assess a person's cancer risk.
Can we reduce our exposure to beta glucuronidase? Taking probiotic supplements increases the proportion of lactobacillus and bifidobacterium in the G.I. tract, which thereby decreases the number of beta-glucuronidase-producing bacteria. A diet that reduces red meat and emphasizes plenty of vegetables and fruits, whole grains and fermented milk products containing live organisms also promotes a healthy population of friendly bacteria.
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Richard N. Podell, M.D., is clinical professor of family medicine at the UMDNJ-Robert Wood Johnson Medical School in New Brunswick, N.J., and director of the Podell Center for Medical Treatment, Prevention and Natural Healing in New Providence, N.J.