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Probiotics, as defined by the Food and Agricultural Organization of the United Nations (FAO), are "live microorganisms administered in adequate amounts which confer a beneficial health effect on the host." The microorganisms referred to in this definition are non-pathogenic bacteria (small, single celled organisms which do not promote or cause disease), and one yeast, Saccharomyces. They are considered "friendly germs," due to benefits to the colon and the immune system. The word probiotic is a compound of a Latin and a Greek word; it means "favorable to life." Probiotics is also sometimes used to refer to a form of nutritional therapy based on eating probiotic foods and dietary supplements. Although probiotic supplements have also been used with farm animals, most are produced for human consumption in the form of dairy products containing two types of microbeslactobacilli and bifidobacteria. As with the extended use of royal jelly , probiotics are now also being used in face creams and similar cosmetic products.

A new category called prebiotics now also appears in the literature. Prebiotics refer mainly to certain foods, and occasionally to certain food products, that support probiotic microorganism viability, enhancing their survivability. Included among prebiotics are foods such as Jerusalem and regular artichokes, oats, leeks, onions, and whole grain breads or cereals. Examples of prebiotic food products are the Fructooligosaccharides (fructooligo-saccharides, or fruit derived, digestion resistant sugars) (FOS), also in honey, and the galactooligosaccharides (galacto-oligo-saccharides), sugars in galactose-containing foods like goats milk.


Although the term probiotics is relatively recent, as are science-based investigations, the use of probioticcontaining fermented foods in many cultures of the world predates the advent of refrigeration. The applied notion of improving health by supplementing the natural microflora of the human intestines with additional bacteria taken by mouth goes back to the late nineteenth century. At that time, some physicians attributed sickness and the aging process to a build up of waste products (or, putrefaction) in the colon (the lower part of the large intestine that empties into the rectum), and toxic materials leaking from the colon into the bloodstream. The process of leakagenow referred to as gut permeability or leaky gut syndromeand the poisoning that resulted from it, were called autointoxication. The autointoxication theory assumed that dietary changes aimed at reducing toxic decomposition in the colon would be beneficial to health. Some observers knew about the use of lactic acid bacteria in sausage-making to ferment the meat and protect it from spoilage. Because these bacteria are harmless to humans, it was thought that adding them to the diet by eating fermented foods would reduce the amount of toxins produced in the colon. The Lactobacilli group of bacteria, some of which are found in yogurt, was the first identified probiotic. In the 1920s and 1930s, many doctors recommended acidophilus milk, which contains the lactobaccili bacterium called Lactobacillus acidophilus, for the treatment of constipation and diarrhea . This treatment was effective for many patients.

The next phase in the development of probiotics came in the 1950s, when medical researchers began to study L. acidophilus as a possible answer to some of the digestive side effects of taking antibiotics. It was known that antibiotic medications upset the natural balance of the intestinal microflora by killing of the beneficial as well as the pathogenic bacteria. The researchers thought that taking oral preparations of L. acidophilus might offset the side effects of the antibiotics.

One of the chief difficulties in benefiting from probiotic supplementation has been assuring survivability of the bacteria as it passes through the acidity of the stomach and the digestive processes of the small intestine and successfully colonizing in the colon. Recently, a new probiotic with exceptional survivability and colonization characteristics, as demonstrated in studies, has emerged. This probiotic, screened from many strains of lactobacilli and named after its co-discoverers, Sherwood Gorbach and Barry Goldin, is known as Lactobacillus GG (LGG). LGG was demonstrated effective against psuedomembranous colitis, an infection of the colon by Clostridium difficile as a result of antibiotic overkill of beneficial bacteria, and against atopic eczema in children due to gut permeability. LGG was demonstrated to have positive results against Candida in mice, as well. Three patents have been awarded on LGG from June 1989 to May 1995. In 1987, a Finnish dairy cooperative, Valio, Ltd., was granted a license to conduct research. About 1992, Valio released a fermented milk product with LGG called Gefilus. In 1996, a division of an American corporation was formed, called CAG Functional Foods, which markets LGG as the product Culturelle. One source reported significant benefit from the use of Culturelle when cultured in milk. Culturelle is currently available only in capsules, but a yogurt product is anticipated to be marketed soon.

Much of the research and marketing of proven probiotics is conducted outside the United States. One such research proven probiotic strain is Lactobacillus plan-tarum 299v. It has been particularly valuable in irritable bowel syndrome (IBS) and recovery from surgery. It's colonization ability was proven using biopsy. It is not currently available in the United States, but agreements with the makers and distributors of Danon yogurt may change that.

Two proven beneficial strains marketed in the United States are Lactobacillus reuteri, a Swedish product proven effective against diarrhea in children due to a rotavirus (a virus transmitted from feces), available in the Stoneyfield brand of yogurt, and Saccharomyces boulardii, a yeast product available in capsules effective against antibiotic associated diarrhea.


Probiotic foods and dietary supplements have been recommended as treatments for a variety of diseases and disorders, ranging from problems confined to the digestive tract to general health issues.

Intestinal complaints

To summarize, probiotic organisms, in particular the LGG strain, have been shown to be helpful in managing the following intestinal disorders:

  • Pseudomembranous colitis, a potentially life-threatening inflammation of the colon caused by an overgrowth of the bacterium Clostridium difficile as a result of the patient's having taken antibiotics that causes profuse watery diarrhea, cramps, and low-grade fever.
  • so-called "traveler's diarrhea"
  • acute nonbacterial diarrhea
  • rotaviral diarrhea
  • irritable bowel syndrome (IBS)
  • bacterial overgrowth in the small bowel by organisms such as Helicobacter pylori, implicated in gastric ulcers (studies have demonstrated benefit but not cure)

Lifestyle-related disorders

Some supporters of probiotics go beyond applications limited to treatment of intestinal disorders. In keeping with the theory of autointoxication, they maintain that probiotics are effective in treating a wide range of chronic and acute illnesses thought to result from a condition called intestinal dysbiosis, or poor intestinal health quality due to toxic buildup, putrefaction, and leaky gut syndrome. Intestinal dysbiosis is defined as an imbalance among the various microorganisms in the digestive tract. This imbalance is attributed to a combination of Western high-protein diets, stress , environmental pollution, and allopathic medications. Putrefaction is believed to result from a low fiber diet, chronic constipation or sluggish colon, and poor food combining leading to increased gut fermentation. Leaky gut syndrome is the term used to suggest that the effect of these toxins on the intestinal cell walls is damaging to intestinal integrity, and as a result, large molecules of relatively undigested food and toxins cross the intestinal membrane into the blood stream.

Some alternative practitioners maintain that the following diseases and disorders are directly related to intestinal dysbiosis or may also be beneficially treated with probiotics:

  • mental health problems
  • chronic fatigue syndrome
  • muscular soreness and stiffness
  • autoimmune disorders, including lupus, rheumatoid arthritis, ankylosing spondylitis , enteric arthritis, and Reiter's syndrome (by immune stimulation and repair of the leaking gut)
  • lactose intolerance (by increasing the presence of lactase)
  • infectious diseases
  • high blood pressure (research has demonstrated a systolic blood pressure decrease of 1020 mm Hg with the use of a fermented milk product
  • high cholesterol, (clinical studies have not been conclusive; as one source said, "Evidence is not over-whelming")
  • cancer (by decreasing exposure from gene-altering substances)
  • menopausal problems in women (by improving the liver's ability to detoxify and eliminate hormonal metabolites)
  • vaginosis (once thought to be relatively benign, now implicated in easier transmission of sexual diseases, pelvic inflammatory disease , and pregnancy -related complications, improved by reducing vaginal pH which inhibits growth of unfavorable bacteria)
  • allergies and asthma (a double-blind placebo-controlled study demonstrated a 50% drop in children followed up to two years of age)
  • kidney stones, by inhibiting the absorption of oxalate from the intestines

More specifically, probiotic foods and dietary supplements are claimed to counteract intestinal dysbiosis in the following ways:

  • production of vitamins. Friendly bacteria are said to manufacture vitamin B3, vitamin B6, and folic acid.
  • anti-tumor and anti-cancer activity
  • suppression of pathogenic microorganisms in favor of the non-pathogenic
  • relief of anxiety symptoms through indirect detoxification
  • protection against radiation and other environmental toxins
  • support of the immune system, by reducing immune load
  • recirculation of female hormones in the bloodstream by a cleaner liver and cleaner blood, thus maintaining higher levels of estrogen in menopausal women
  • maintenance of smooth bowel functioning



Probiotics is a nutrition-based therapy and relies primarily on the addition of foods or supplements containing friendly bacteria to the diet. Some recommended foods are ordinary grocery store items that involve fermentation in their production; these include miso, pickles, sauerkraut and fermented dairy products such as yogurt and kefir. As mentioned, other food or food products called prebiotics, such as Jerusalem artichokes and FOS, are thought to support the growth of the beneficial bacteria in the intestines. Most users and recommenders of probiotics, however, encourage the use of loose powdered, refrigerated dietary supplements of friendly bacteria or LGG capsules. Some of these products are milk-based, while others are milk-free. Probiotic dietary supplements are over-the-counter (OTC) preparations that can be easily purchased at grocery or health food stores, or from European manufacturers over the Internet. The types of bacteria most often recommended are Lacto-bacillus GG, Lactobacillus acidophilus, Lactobacillus bulgaricus, and, especially for children Bifidobacterium bifidum. Breast milk is reported to contain nutrients that support bifidobacterium growth.

Dosage and administration

Some practitioners distinguish between a therapeutic dose of probiotic products, which is given for 10 days, and a maintenance dose, which is used afterward. One source gives 25 level tsp (510 g) of powdered supplement as the daily therapeutic dose if the patient is taking L. acidophilus or B. bifidum, 13 tsp (36 g) if the patient is using L. bulgaricus. The maintenance dose of L. acidophilus is given as 0.5 tsp (1 g) daily; of B. bifidum, 2 tsp (4 g) daily; of L. bulgaricus, 0.5 tsp (1 g) with each meal. The recommended dose of LGG capsules is once daily. A dose two or three times daily may also be used initially to overcome acute symptoms.

Patients are advised to take these supplements with spring water, but not with juice or broth. These fluids are thought to stimulate the secretion of stomach acids that will destroy the friendly bacteria.


The fact that probiotic products include some ordinary dairy and grocery items means that most people who use them do not think of them as medications and see no need to consult a health professional. Persons who are taking prescription medications and persons with compromised immune status, however, are advised to consult their doctors before using probiotic dietary supplements. These products often influence the bulk and frequency of bowel movements, thus increasing the elimination rate of some medications and necessitating a dose adjustment.

Some practitioners of nutritional therapies recommend cleansing the lower digestive tract with an enema or colonic treatment before beginning a course of probiotic supplements. Conversely, use of probiotics may be particularly recommended following colonic therapy as it is following antibiotic therapy.


Although the bacteria in probiotic supplements are human-friendly, some persons may have food allergies or a digestive tract that is sensitive to miso, other fermented foods, or the milk powder that may be in some products.

Vegetarians or persons who cannot digest milk-based products may prefer probiotic supplements with a rice base.

Product reliability is a concern because probiotic dietary supplements are not regulated by the Food and Drug Administration (FDA) and because study after study demonstrates the difficulty of maintaining a live probiotic culture, in or out of the body. One study of the microorganisms in 25 dairy products and 30 powdered products found that more than one third of these products contained no living microorganisms, and only 13% of the products contained all of the bacteria types listed on the label. One practitioner suggests the following guidelines for evaluating the effectiveness of probiotic products:

  • Number of viable organisms. A number lower than 1 billion organisms per gram is considered inadequate for a therapeutic dosage.
  • Type of organism. Single-strain products are considered more useful than multi-strain products on the grounds that the different bacteria in multi-strain products may compete with each other.
  • Processing method. Products that have been put through a centrifuge or ultra-filtration system are thought to have fewer viable bacteria.
  • Additives. Products that do not have hormones or other chemicals added to stimulate the growth of the bacteria are considered more effective.
  • Form. Powdered supplements are considered preferable to liquids. Encapsulated powders are second-best, except in the case of LGG capsules.
  • Storage. Probiotic products that are not refrigerated are thought to lose much of their effectiveness.

Side effects

The side effects of treatment with probiotics may include a condition called excessive drainage syndrome, which includes headache , diarrhea, bloating, or constipation. Another commonly reported side effect is intestinal gas . These side effects are attributed to the cleansing of toxins from the body and may last for some days. Practitioners recommend lowering the supplement dosage to reduce the side effects, or pretreating with colonic therapy, or stool softeners and fiber as tolerated or advised by a healthcare professional.

Research & general acceptance

More studies of probiotics have been done in Europe than in the United States, which is reflected in the fact that the leading manufacturers of probiotic supplements are presently based in Europe. Some mainstream researchers in Europe as well as in the United States are skeptical of some of the claims made for probiotics. Their reasons include the following considerations:

  • The studies done in support of probiotics are mostly anecdotal or heavily reliant on test-tube experimentation rather than on clinical trials in human subjects. As of 2000, relatively few strains of probiotic bacteria have been shown to have clinical value. These strains are helpful in treating milk allergy and irritable bowel syndrome in humans, and in improving resistance to a yeast called Candida in immunocompromised mice.
  • The basic concept of probiotics is based on a misunderstanding of the role of microflora in the human digestive tract.
  • It is difficult to see how bacteria taken by mouth can survive the process of human digestion. At present, only two species of lactobacilli, L. GG and L. plan-tarum 299v, have been shown to be able to colonize the human gut.
  • Supporters of probiotics emphasize two types of bacteria, the lactobacilli and the bifidobacteria, and virtually ignore the hundreds of other species that live in the intestines.

More clinical studies examining the effects of probiotics on specific conditions are being conducted. One such study in the making will examine the effect of probiotics on hepatic steatosis, or fatty degeneration of the liver. An inclusion criteria was biopsy diagnosis of non-alcoholic fatty liver disease. The study is expected to be completed in October 2004.

Training & certification

As of 2000, there are no training or certification programs specifically for probiotics. Most practitioners who recommend probiotics have been trained as nutritionists or naturopathic physicians.



Chaitow, Leon, ND, and Natasha Trenev. Probiotics. Northampton, UK: Thorsons, 1990.


American Academy of Alternative Medicine (AAAM). 16126 E. Warren, Box 24224. Detroit, MI 48224-0224. (313) 882-0641. Fax: (313) 882-0972.

Ontario College of Naturopathic Medicine. 60 Berl Avenue. Toronto, Ontario M8Y3C7.


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Rebecca Frey, Ph.D.

Katherine E. Nelson, N.D.

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Probiotics is a term that refers to the consumption of certain microorganisms in an effort to improve overall health and the functioning of the body's microflora.

The use of microorganisms as a health aid is not new. People have asserted the health fortifying attributes of yogurt and fermented milk for thousands of years. However, the cause of the beneficial effect was unknown. A century ago, the Russian microbiologist Élie Metchnikoff (18451916) began the scientific assessment of the probiotic role of microorganisms.

Based on Metchnikoff's work and that of others, it appeared well established (but not clinically proven) by the 1920s that Lactobacillus acidophilus acted to relieve the conflicting conditions of constipation and diarrhea. Capsules containing living bacteria were popular items in drug stores of the day. However, with the advent of antibiotics as a cure for many ailments, the public interest in probiotics waned. The emphasis shifted to the treatment of infections, as opposed to the prevention of infections.

In the 1990s the interest in probiotics surged. A number of studies established the clinical significance of Lactobacillus and Bifidobacterium in improving the efficiency of lactose absorption, in the treatment of diarrhea in children, and in combating recurrent vaginal yeast infections.

Probiotic bacteria exert their effect by colonizing surfaces, such as found in the intestinal tract or the vagina. Compounds can also be produced by the adherent bacteria that are inhibitory to other types of bacteria. The net effect of these processes is the competitive exclusion of potentially harmful bacteria by the beneficial probiotic bacteria.

The exclusion process can extend to other infectious agents as well. For example, colonization of the intestinal tract with Lactobacillus GG has been shown to significantly reduce the length of diarrheal illness caused by rotavirus. The rotavirus had no place to adhere and were washed out of the intestinal tract.

Probiotics also have shown potential in relieving skin disorders that are the result of an allergic reaction to a food. The colonization of the intestinal wall appears to restore the ability of nutrients to cross from the intestinal canal to the bloodstream. This ability to absorb food nutrients is disrupted in those with some food allergies .

The molecular basis for the competitive exclusion behavior of bacteria such as Lactobacillus and Bifidobacterium is the subject of continuing study. The identification of the precise molecular agents that are responsible for surface blocking will expand the use of probiotics.

See also Lactobacillus; Microbial flora of the stomach and gastrointestinal tract

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Probiotics are live, nonpathogenic microorganisms that may interact with gastrointestinal and vaginal microflora . Clinical studies indicate that certain probiotics may be useful in treating some diarrheal disorders, respiratory allergies , and eczema , as well as in controlling inflammation and reducing the risk of candidal vaginitis and colon cancer .

Dietary sources of probiotics are usually found in dairy products. Yogurt, for example, contains intestinal species of lactobacilli and bifidobacteria, two groups of probiotic bacteria. Gastric survival rates of probiotics are estimated at 20 to 40 percent, with the main obstacles to survival being gastric acidity and the action of bile salts. Investigations into different modes of administering probiotics may expand their applications in functional foods .

see also Functional Foods.

M. Elizabeth Kunkel Barbara H. D. Luccia


Gibson, G. R., and Roberfroid, Marcel B. (1999). Colonic Microbiota, Nutrition, and Health. Boston: Kluwer Academic.

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probiotics Preparations of live micro‐organisms added to food (or used as animal feed), claimed to be beneficial to health by restoring microbial balance in the intestine. The organisms commonly involved are lactobacilli, bifidobacteria, streptococci, and some yeasts and moulds, alone or as mixtures. The idea that friendly bacteria in yogurt will crowd out pathogenic organisms originally propounded by Russian‐French bacteriologist Ilya Metchnikoff (1845–1916) in The Prolongation of Life (1907). See also prebiotics.

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"probiotics." A Dictionary of Food and Nutrition. . 13 Dec. 2017 <>.

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