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The Promise of Probiotics

You may not know the term “probiotics,” but you’ve probably already eaten them. Yogurt, aged cheese, and other cultured and fermented foods make up this category of “super foods” now known world-wide. A probiotic— literally, “for life” in Greek—is defined as “a preparation or a product containing a sufficient number of live microorganisms to alter the flora of the host and bring about beneficial health effects.” In short, probiotics are “good bacteria” we import into our system to hold more dangerous microbes in check.

Yogurt, the most popular probiotic, has been around at least 4,000 years, and has been linked to long life for centuries. In fact, a Russian immunologist named Ilya Mechnikov received a Nobel prize in the early 1900s for his studies on the unusual longevity of Bulgarian peasants. He learned these peasants ate a diet high in fermented foods, including yogurt and other foods containing a bacterium he named Lactobacillus bulgaricus

In Japan and Europe, live-culture dairy products have enjoyed great popularity for decades. A growing number of scientific studies have found that probiotics can aid both digestive and immune system health. If you watch US television commercials, you know the probiotics movement has spread, with mass-market dairy products promising to help you “reduce bloating and get regular” and to “strengthen your body’s defenses.”

Jumping on the probiotics bandwagon is easy—the foods (or supplements) are safe and widely available. Most people find them both tasty and easy to digest. But are they really effective? Is it a “one size fits all” solution, or should some people seek out particular types of bacteria? How can you make sure you’re getting enough live bacteria to make a difference?

To take full advantage of probiotics, you need to begin by learning a little bit about the place you want their “good” bacteria to wind up: your gastrointestinal tract.

Welcome Inside “Microbe City”

The human body contains 100 trillion cells, and 90% of them are not even our own—they are tiny, one-celled life forms known as microorganisms or microflora. Nearly all of these are bacteria; the rest are yeasts and parasites. These bacteria are incredibly diverse in size, shape, color and growth rates, and may include as many as 1,000 different species.

Most of our bacterial guests, called “normal flora,” reside in our gastrointestinal tract, primarily in the places shown in the figure at left, including:

  • Oral Cavity (mouth, nose, throat): Millions of bacteria live in a single teaspoon of saliva, including “bad” types linked to halitosis and gingivitis.
  • Stomach: Few bacteria live here due to very high acidity, but one is Heliobacter Pylori, which can cause ulcers and stomach cancer. Lactobacillus can help keep H. Pylori in check.
  • Reproductive Tract: A healthy vagina contains thousands of different types of bacteria, with the majority being a type of Lactobacillus.
  • Small Intestine: Millions of bacteria live in this organ, where they receive nutrients in exchange for helping us digest food, make vitamins, and stimulate our immune system. Most of these bacteria are benign species of Streptococcus and Enterococcus.
  • Colon: Billions of bacteria, predominantly Bacteroides, live in the colon or large intestine, the final stop in digestion, where wastes are stored and excreted in the stool. The stool contains over 500 different types.

These microbes enter our body through the air we breathe, and the food and drink we consume. Once stuck in the mucous that lines our oral and nasal cavities, they are swallowed and propelled through our digestive system.

In this teeming “inner city,” microbes compete for food and space in the mucosal surfaces that line our digestive tube. The relationship is symbiotic; we give the bacteria room and board in exchange for labor, mainly breaking down our food. Although there are widespread “employment opportunities” in food digestion, most digestive organs offer lousy accommodations. All the acid and churning causes microbes to head for the choice real estate of the intestines, with their long coils of cushy, mucosal folds. Most gut bacteria actually reside in the large intestine (colon), the most hospitable and final stop in digestion, where water is absorbed from indigestible food matter and waste is stored and then removed from the body.

Among our body’s microbes, you can find the “good” (probiotics like Lactobacillus, a common bacteria in yogurt), the “bad” and the “risky.” In this final group are several bacterial species that benefit us when they are in the right place, and in the right numbers. For example Klebsiella make vitamins B12 and K when they’re inside our small intestine but, in our lungs, they can cause pneumonia.

In a healthy gut, friendly bacteria are plentiful enough to keep the dangerous and potentially harmful bacteria under control. Unfortunately, many of us find their numbers lacking, says Gary B. Huffnagle, PhD, a professor of internal medicine, microbiology and immunology at the University of Michigan Medical Center. “New research is revealing that the [probiotic] population often isn’t large enough for optimal health,” writes Dr. Huffnagle in his book The Probiotics Revolution.

Aside from their role in proper digestion, Dr. Huffnagle maintains that probiotics are also vital to our immune system. “They actually send signals to the immune system that reduce destructive overreactions, including inflammation. This means that insufficiencies affect immune responses—and therefore every aspect of our health.”

The chart below identifies some of the autoimmune disorders suspected to be associated with a bacterial overgrowth.

In addition to affecting our immune system, the microbial imbalance in our gut can affect other systems in our body, including our hormonal system.
As you may know, the digestive system plays an important role in the proper disposal of estrogens from the body. When the flora in our intestines is disturbed, estrogen that should be excreted can be recycled and reabsorbed into the bloodstream, creating hormone imbalance.

The Gut as an Immune Organ

According to Kelly Dowhower Karpa, PhD, RPh, the gastrointestinal 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 act appropriately to fight disease-causing substances, while tolerating normal foods and normal flora. As we grow up, this “oral tolerance” becomes the cornerstone 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.


Dr. Karpa says that since the late 1950s, the incidence of immune-related conditions, from allergies to inflammatory diseases, has exploded in Western societies. Many researchers believe environmental changes are involved, in particular, increased hygiene practices and unbalanced, processed-food diets. “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,” Dr. Karpa explains.

The widespread use of antibiotics over the same period must also be considered, stresses S.K. Dash, PhD, founder and president of UAS Laboratories, a leading probiotic company. “Antibiotics can be the biggest culprits in destroying our friendly bacteria,” writes Dash 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.”

Suspected Associations Between
Autoimmune Disorders & Bacterial Overgrowth

DisorderType of Bacteria
Ankylosing SpondylitisKiebsiella
Graves’ disease and Hashimoto’s diseaseYersinia
Guillain-Barre syndromeCampylobacter
Multiple sclerosisChlamydia
Rheumatic feverStreptococcus Pyogenes
Rheumatoid ArthritisCitrobacter, Kiebsiells, Proteus, Porphyromones
Autoimmunity, in generalEscherichia coli, Proteus

Even if you don’t take antibiotic medications, Dash points out that meat eaters still consume them, since most US cattle, pigs and poultry receive antibiotic feed. He strongly urges those taking prescription antibiotics to use probiotics at the same time to replenish their stock of beneficial bacteria.
According to Dr. Karpa, the presence of bacteria in the gut stimulates production of cytokines, which are signals to the immune system to trigger inflammation and allergies. Different species of bacteria stimulate the release of different cytokines.

We know that allergic reactions happen when the immune system overreacts to harmless substances. Some studies show taking probiotics during pregnancy can help prevent babies from developing eczema, notes Dr. Huffnagle, who adds that probiotics are “under intense investigation as an allergy treatment.” Autoimmune diseases may also be helped by probiotics someday, he believes, “because they signal the immune system to show restraint.”

Inflammatory Bowel Disease, Crohn’s Disease and Irritable Bowel Syndrome

Sometimes, a malfunctioning of the immune system leads to chronic inflammation of the intestines, resulting in inflammatory bowel disease (IBD), which affects 60 to 70 million Americans. Specific forms of this disease range from the relatively mild Irritable Bowel Syndrome (IBS) to the most severe form, Crohn’s Disease. Studies show that people with IBD have lower levels of probiotics in their gastrointestinal tracts than do healthy people.

IBS is characterized by bowel pain, bloating, either diarrhea or constipation, and gas. IBS is a frustrating disease because it has no known cause, and doesn’t coincide with any visible damage to digestive organs, so it is diagnosed only after the other forms of IBD have been ruled out. It affects three times as many women as men. As many as 20% of US women 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. Treatment usually includes anti-inflammatory drugs injected into the intestinal tract. For some, medications fail and surgery is required.

Even when the immune system is not implicated, a number of very common gastrointestinal illnesses—ranging in severity from mild stomach upset to life-threatening, chronic ailments—do occur when there is an imbalance in gastrointestinal flora.


Nearly everyone has struggled with diarrhea, 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.
Acute diarrhea, whatever its cause, remains the world’s leading cause of illness and death, as dehydration quickly proves deadly where treatment is unavailable. Yet, 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.

While probiotics are generally advised for preventing but not actually treating disease, in the case of diarrhea, some studies show probiotics can actually heal. “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 healing.

In general, probiotics are a boon to good digestion. Probiotics in the intestines make shortchain fatty acids (needed for GI tract health), antioxidants, amino acids and vitamin K. Nutrients in fermented foods are more readily absorbed than the nutrients in non-fermented foods. Fermented foods are those in which an agent such as a yeast, bacterium, mold or enzyme is used to break a substance down into simpler substances; examples include converting milk to yogurt or cheese, fermenting soy to make miso, and fermenting cabbage to make kimchi or sauerkraut.


The presence of probiotics in the gut also inhibits the growth of yeasts by producing pH-lowering lactic acid (and sometimes other acidic substances). A strain of yeast called Candida albicans (candida for short) is a normal component of our digestive system. However, when the pH balance is tipped, often by antibiotics or a diet high in sugar and starches, a candida overgrowth may occur, resulting in candidiasis (commonly called a yeast infection). In the intestines, this can 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 which can trigger a host of problems, including chronic fatigue, headache, and depression, as well as an avalanche of food allergies.

Vaginal and Urinary Tract Infections

Candida overgrowth also occurs in other organs, notably the vagina. The use of oral contraceptives, standard hormone replacement therapies, and especially antibiotics increases a woman’s risk for vaginal candidiasis.

Antifungal medications are prescribed to treat the symptoms, but they typically recur unless the GI tract can be recultivated with friendly bacteria. Probiotics have been conclusively 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 also benefit from increased use of probiotics. For example, problems associated with vaginitis (inflammation of the vagina) can affect women of all ages, causing vaginal discharge and pain. In younger women, the discharge and pain are usually the result of an imbalance of harmful bacteria. This can be very serious when it occurs to pregnant women, since it can cause premature labor.

Postmenopausal women often get atrophic vaginitis—inflammation resulting when estrogen levels drop. This scenario causes increased vaginal pH and predisposes these women to vaginal pain and discharge, and also to urinary tract infections (UTIs). While UTIs are easily treated, they often come back.

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, the authors cite a clinical study showing that women who took freeze-dried L. rhamnosus GR-1 and L. fermentum RC-14 were much less likely to get bacterial vaginosis, and that their levels of protective Lactobacilli bacteria were also higher, indicating protection from yeast overgrowth.

Value of Probiotics

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.

In his book, Dr. Huffnagle remarks at how prescient Chinese doctors were centuries ago: “They somehow knew that the intestines were not merely a digestive organ, but the center of health and well-being.” Today, he adds, modern medicine is confirming their wisdom with clinical studies and laboratory tests, which add knowledge on the effects of various bacterial strains. For example, he says the value of probiotics in supporting overall health can be seen in a recent German clinical trial that showed healthy working adults taking Lactobacillus and Bifidobacterium supplements have fewer, less severe colds and higher white cell counts.

Yet, getting a beneficial effect for any individual’s specific health needs depends on several factors, including:

  • the strain of bacteria selected and how your body is able to utilize it
  • the numbers of live bacteria in the purchased product, and whether they are stored and taken properly.


In order to boost the effectiveness of probiotics, adding dietary fiber or prebiotics to your diet is highly recommended. Prebiotics, says Dr. Dash, are “carbohydrates that selectively feed beneficial bacteria in the intestinal tract and stimulate their growth.” He explains that prebiotics may be thought of as “fertilizer” for the good bacteria in the GI tract. Examples include polydextrose, inulin, and fructooligosaccharides (FOS), also sometimes called oligofructose or oligofructan. Prebiotic foods include whole grains, fruits, vegetables, red wine and dark chocolate. In addition, some of these foods also contribute to a fiber-rich diet, which helps relieve constipation—yet another benefit realized from probiotic use. Although it’s best to get fiber from whole foods, fiber supplements can be valuable, particularly if they include soluble fiber sources and are taken with lots of water.

Safety, Storage and Use

Probiotics are very safe for the majority of people, with the exception of those at very high risk for infections of all types, such as those with HIV/AIDS or cancer, or those taking 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.”

How should you take your bacteria: pill or plate? Either form will work, as long as you follow the proper procedure. Foods containing live cultures must be kept refrigerated, and storage dates must be strictly followed. Although it might seem that pill supplements would be required for the lactose-intolerant among us, you may be surprised to learn that is not necessarily the case. Probiotics have actually been shown to help break down lactose (milk sugar), reducing symptoms of the illness and allowing sufferers to reintroduce dairy into their diet—at least in the form of yogurt and other fermented products.

Care must be taken when purchasing a probiotic—in any form—to help ensure you are receiving the promised bacterial strain and number of live bacteria, properly stored. All too often, Dr. Karpa notes, the bacterial strains listed on a label are not the actual strains in the product.

This leads some observers to suggest cutting out the middleman. Frank Murray provides a recipe for making your own yogurt in his book Acidophilus and Your Health. He also includes this advice for purchasing yogurts: Always purchase yogurt with “live, active cultures” including Lactobacillus acidophilus, and avoid frozen yogurt and pudding-style yogurt which add stabilizing chemicals and artificial sweeteners.

Quite frequently, probiotic foods (unless very carefully made or purchased) just don’t supply enough active bacteria to alter the gut flora. In order to give your probiotics a better chance of success, make sure to take them on an empty stomach and to add more dietary fiber, or prebiotics (see box above) to your meals.

Recommendations from your healthcare practitioner may help guide you to reliable products from proven manufacturers. “By selecting quality products, using appropriate storage conditions and ingesting probiotics on an empty stomach, you can obtain maximal benefits from taking probiotics,” sums up Dr. Karpa.

Connections is a publication of Women’s International Pharmacy, which is dedicated to the education and management of PMS, menopause, infertility, postpartum depression, and other hormone-related conditions and therapies.

This publication is distributed with the understanding that it does not constitute medical advice for individual problems. Although material is intended to be accurate, proper medical advice should be sought from a competent healthcare professional.

Publisher: Constance Kindschi Hegerfeld, Executive VP, Women’s International Pharmacy
Co-Editors: Julie Johnson and Carol Petersen, RPh, CNP; Women’s International Pharmacy
Writer: Kathleen McCormick, McCormick Communications
Illustrator: Amelia Janes, Midwest Educational Graphics

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