The Gut as an Immune Organ
According to Kelly Dowhower Karpa, PhD, RPh, the GI tract is the largest immune organ in the body. In her book Bacteria for Breakfast, Dr. Karpa describes how gut bacteria communicate with immune system cells within the walls of our intestines. This instant messaging helps ensure immune cells fight disease-causing substances while tolerating normal foods and flora; as we grow up, this “oral tolerance” becomes the foundation of a mature immune system.
“Normal gut bacteria acquired in infancy are likely to be the most important determinants of allergies and diseases of chronic inflammation later in life,” Dr. Karpa writes. Some studies show taking probiotics during pregnancy may help prevent babies from developing eczema, notes Dr. Huffnagle, who adds that probiotics are “under intense investigation as an allergy treatment.” He believes that probiotics may also be used to help autoimmune diseases “because they signal the immune system to show restraint.”
Allergic reactions happen when the immune system overreacts to harmless substances. Dr. Karpa says that the incidence of immune-related conditions, from allergies to inflammatory diseases, has increased in Western societies since the late 1950s. Many researchers believe environmental changes are involved: in particular, increased hygiene practices and unbalanced, processed-food diets.
To Dr. Karpa, this indicates that “exposure to various types of bacteria—through dietary sources and by actually getting sick and letting the immune system do its job—makes a dramatic impact on the development of allergic diseases.” According to Dr. Karpa, the presence of bacteria in the gut stimulates cytokine production, which signals the immune system to trigger inflammation and allergies. Different species of bacteria stimulate the release of different cytokines.
The widespread use of antibiotics over the same period must also be considered, stresses S.K. Dash, PhD, founder and president of the probiotic company UAS Laboratories. “Antibiotics can be the biggest culprits in destroying our friendly bacteria,” Dr. Dash writes in The Consumer’s Guide to Probiotics. “At high dosages, they can wipe out all bacteria inside your body, the good along with the bad. Once that happens, the race is on to as to which microorganisms, the good guys or the bad guys, set up shop.”
Even without taking antibiotic medications, Dash points out that meat-eaters still consume them, since most US cattle, pigs and poultry receive antibiotic feed. He urges those taking prescription antibiotics to use probiotics at the same time to replenish friendly microbes.
Inflammatory Bowel Disease, Crohn’s Disease, and Irritable Bowel Syndrome
Immune system malfunction sometimes leads to chronic inflammation of the intestines, resulting in inflammatory bowel disease (IBD), which affects 60-70 million Americans. Specific forms of this disease range from the relatively mild Irritable Bowel Syndrome (IBS) to a more severe form, Crohn’s Disease. Studies show that people with IBD have a greater tendency for microbial imbalance in the gut when compared with healthy people.
IBS is characterized by bowel pain, bloating, diarrhea or constipation, and gas. IBS has no known cause and doesn’t coincide with any visible damage to digestive organs, so it is diagnosed only after other forms of IBD have been ruled out. It affects three times as many women as men: as many as 20% of women in the US are believed to suffer from IBS at some point in their lives. Probiotics have had mixed results in treating IBS. However, one Irish clinical study showed significant improvement when IBS patients took a daily drink of Bifidobacterium infantis.
In Crohn’s Disease, deep inflammatory lesions affect the lower part of the small intestine and the colon. (A similar condition, ulcerative colitis, is characterized by smaller lesions plaguing only the colon.) The resulting thickening and swelling of the bowel wall can cause deep intestinal obstruction, which can become life threatening. Patients frequently endure cycles of extreme pain and weight loss with periods of remission.
Even when the immune system is not implicated, several common gastrointestinal illnesses—ranging in severity from mild stomach upset to life-threatening, chronic ailments—occur when there is an imbalance in the microbiome. Treatments include anti-inflammatory medications injected into the intestinal tract, immune-suppressive, and immune-modulatory medications. For some, however, medications fail and surgery is required.
Diarrhea is often the result of viral gastroenteritis (usually caused by rotavirus or norovirus) or Traveler’s diarrhea (following ingestion of water contaminated by fecal bacteria such as E. coli). Some people develop severe diarrhea after exposure to an antibiotic-resistant strain of bacteria known as C. difficile. This often occurs in a hospital or other institutional setting, following a course of antibiotics.
Whatever its cause, acute diarrhea remains the world’s leading cause of illness and death. Dehydration may prove deadly where treatment is unavailable. Even with modern medical care, those who suffer from C. difficile often endure painful, recurring bouts with diarrhea whose symptoms may include a life-threatening form of colitis.
Probiotics are generally advised for preventing but not treating disease. In the case of diarrhea, however, some studies show probiotics may have healing properties: “Lactobacillus CG at high doses for 7-10 days after antibiotics has cured patients with relapsing C. difficile,” says Dr. Karpa. In addition, studies show Lactobacilli can treat and prevent rotaviral diarrhea, shortening the duration of diarrhea and speeding the healing process.
A strain of yeast called Candida albicans (Candida for short) is a normal component of our digestive system. However, when pH becomes unbalanced—often by antibiotics or a diet high in sugar and starches—Candida overgrowth may occur, resulting in candidiasis (commonly called a yeast infection). This may cause a wide range of chronic digestive problems, such as bloating and heartburn.
Sometimes the Candida organism bores into the gut wall, releasing powerful toxins and incompletely-digested dietary proteins into the bloodstream. The immune system then produces antibodies, causing allergic reactions that may trigger a host of problems, including chronic fatigue, headache, and depression, as well as a multitude of food allergies. Bacteria in the gut inhibit the growth of yeasts by producing pH-lowering lactic acid (and sometimes other acidic substances).
Vaginal and Urinary Tract Infections
Candida overgrowth also occurs in other parts of the body, notably the vagina. Use of some medications, especially antibiotics, increases a woman’s risk for vaginal candidiasis. Symptoms are often treated by prescribing antifungal medications but typically recur unless the GI and genital tracts are replenished with friendly bacteria.
Probiotics have been shown to help restore the normal yeast-bacteria balance in the body. “Products that stimulate L. acidophilus or B. bifidum can help immensely as part of a comprehensive program that addresses the whole person,” says Dr. Dash.
Other imbalances in the vagina and the urinary tract may benefit from increased use of probiotics. For example, problems associated with vaginal inflammation (vaginitis) may affect women of all ages, causing vaginal discharge and pain. In younger women, these symptoms usually result from an imbalance of harmful bacteria. This may be serious when it occurs in pregnant women since it may cause premature labor.
Postmenopausal women often develop atrophic vaginitis—inflammation resulting when estrogen levels drop and the tissues become thinner and drier. This scenario increases vaginal pH and predisposes these women to vaginal pain and discharge and also to urinary tract infections (UTIs) and vaginal infections. Usually these infections are easily treated; however, they often recur. Additionally, the antimicrobials used to treat these infections further disrupt the microbial balance in the area.
Clinical evidence shows that probiotics may help prevent and even treat urogenital tract problems. In their chapter on these conditions in The Power of Probiotics, Dr. Gary Elmer et al. cite a clinical study of women who took freeze-dried L. rhamnosus GR-1 and L. fermentum RC-14. The results showed these women were less likely to get bacterial vaginosis, and that their levels of protective Lactobacilli bacteria were also higher, indicating protection from yeast overgrowth.
The Value of Probiotics
In general, probiotics promote healthy digestion. Microbes in the intestines make short-chain fatty acids (needed for GI tract health), antioxidants, amino acids, and vitamin K. Nutrients in fermented foods absorb more readily than nutrients in unfermented foods. Fermented foods use agents such as yeast, bacterium, molds, or enzymes to break down a substance into simpler substances; examples include converting milk to yogurt or cheese, fermenting soy to make miso, and fermenting cabbage to make kimchi or sauerkraut.
With growing alarm over the spread of virulent strains of antibiotic-resistant bacteria, many people are eager to try approaches to illness prevention and treatment that do not require the use of antibiotics. Getting a beneficial effect for individual health needs, however, depends on various factors, including:
- The strain of probiotics selected and how the body can use it
- The numbers of live probiotics in the purchased product, and whether they are stored and taken properly
In his book, Dr. Huffnagle remarks on the foresight of Chinese doctors centuries ago: “They somehow knew that the intestines were not merely a digestive organ, but the center of health and well-being.” Modern medicine is confirming their wisdom with clinical studies and laboratory tests, which add knowledge about the effects of various bacterial strains.
Safety, Storage, and Use of Probiotics
Probiotics are safe for the majority of people, except for those at high risk for infections of all types (such as those with HIV/AIDS or cancer), or those taking immune-suppressive steroids. It is always advisable to check with your practitioner before taking any new supplements, as probiotics do have the potential to interact with some medications. Moreover, your practitioner can help you select the probiotic that is best suited to treating your particular condition, notes Dr. Karpa: “You may have to search for the right probiotic, the appropriate number of microorganisms, or the necessary combination of probiotics until you find the right mix to successfully fill the bacterial niche missing in your gastrointestinal tract.”