In Praise of Probiotics – Good Bacteria are Your Belly’s Best Friends

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Updated November 1st, 2021

Over 400 species of bacteria weighing almost 4 pounds (1.5 kilos) inhabit the digestive tracts of healthy humans.  Live bacteria (a.k.a. the intestinal flora) make up 30% of the fecal mass. Some of these thousands of billions of bacteria are hostile and can cause disease, while many are friendly and have established a symbiotic, mutually beneficial relationship with us over the millennia.  These friendly bacteria have also been referred to as “probiotics” and are being used increasingly by mainstream clinicians for both preventive and therapeutic purposes. The literal translation of the word probiotic is “for life.”

Probiotics offset other intestinal bacteria that produce putrefactive and carcinogenic toxins. If harmful bacteria dominate the intestines, essential vitamins and enzymes are not produced and the level of harmful substances rises leading to cancer, liver and kidney disease, hypertension, arteriosclerosis and abnormal immunity. Harmful bacteria can proliferate under many different circumstances including peristalsis disorders, surgical operations of the stomach or small intestine, liver or kidney diseases, pernicious anaemia, cancer, radiation or antibiotic therapies, chemotherapy, immune disorders, emotional stress, poor diets and aging.

The best known of the probiotics are the Lactobacilli, a number of species of which (acidophilus, bulgaricus, casei and sporogenes) reside in the human intestine in a symbiotic relationship with each other and with other microorganisms (the friendly Streptococci, E. coli and Bifidobacteria). Lactobacilli are essential for maintaining gut microfloral health, but the overall balance of the various microorganisms in the gut is what is most important.
Another probiotic which has recently generated a great deal of interest is the friendly yeast known as Saccharomyces boulardii, an organism that belongs to the Brewer’s Yeast family, not the Candida albicans group. S. boulardii is not a permanent resident of the intestine but, taken orally, it produces lactic acid and some B vitamins, and has an overall immune enhancing effect. In fact, it has been used therapeutically to fight candida infections.

Benefits of Probiotics

The following are the most well documented benefits of  taking probiotics regularly:
• Weaken antibiotic resistant bacterial strains,  attack new types of pathogens (supergerms) and infections in immuno-compromised people requiring treatment (i.e. resist opportunistic infections like candidiasis)
• Manufacture B vitamins (biotin, B3, B5, B6, folic acid, B12) and vitamin K
• Secrete lactase, an enzyme required to break down lactose in milk
• Act as anti-cancer factors (especially for bladder and bowel) by inhibiting bacteria that convert nitrates into nitrites
• Inhibit bacteria that secrete carcinogens
• Function as natural antibiotics against unfriendly bacteria, viruses and yeast like Candida albicans
• Enhance bowel function and elimination; prevent constipation
• Reverse diarrhea conditions (Crohn’s disease, AIDS, Traveller’s)
• Reduce or eliminate bloating, gas, straining and abdominal pain due to any cause
• Prevent skin problems, especially acne and other skin infections. (FYI – most chronic acne conditions in adults are often improved or eliminated by a good bowel flora balance).
• Protect against the adverse effects of radiation and pollutants
• Reduce blood levels of cholesterol and triglycerides
• Fight stress and food cravings and thereby prevent or reverse obesity
• Help eliminate bad breath
• Optimize sex hormone levels, enhance fertility and prevent osteoporosis
• Produce lactic acid, improve the digestibility of foods
• Oppose putrefactive bacteria like bacteroides associated with a meat-rich diet
• Treat eczema, psoriasis, ulcerative colitis, Crohn’s Disease, irritable bowel syndrome, all cancers, gastritis, duodenitis, diverticulitis, food allergies, lactose intolerance, environmental allergies, urinary tract infections, vaginitis, other chronic infections (TB, AIDS, Herpes, venereal diseases) and autoimmune diseases (e.g. rheumatoid arthritis, polymyalgia rheumatica, ankylosing spondylitis, psoriasis, lupus, alopecia areata, scleroderma, thyroiditis, etc.)

Probiotics and Pregnancy

The use of probiotics to balance the bacterial ecology of the vagina and intestine favourably influences the course of pregnancy, labour, and the postpartum period.  Far safer than prescription antibiotics, Lactobacilli and other probiotics have been documented to reduce the incidence of postpartum complications.

Clostridium Difficile

Clostridium difficile can cause life threatening diarrhea, especially in hospitalized patients who have been exposed to broad spectrum antibiotics. It is often resistant to commonly prescribed antibiotics given both orally as well as intravenously. The good news, however, is that in 2012, at least 20 studies found that the use of probiotics prevents Clostridium difficile-associated diarrhea by 75%. These studies used a combination probiotic (several species per dose) product containing 10 billion organisms daily.

Friendly bacteria work to enhance bowel function and elimination, and alleviate constipation.

How They Work

Probiotics work in many different ways by their production of antimicrobial substances (organic acids, hydrogen peroxide, and bacteriocins) that inhibit pathogen adhesion and degrade toxins produced by microbial invaders.  Probiotics resist colonization by competing for binding sites as well as for nutrients with pathogens.  In other words, they crowd out pathogens like candida and harmful E. Coli.
Probiotics secrete various proteins that stimulate the immune system both locally and throughout the body, boost intestinal brush border enzyme activity and increase secretory-IgA (a family of antibodies lining mucous membranes).  Enzymes like lactase, sucrase, maltase, alpha-glucosidase, and alkaline phosphatase are enhanced by probiotics.  Cholesterol and triglyceride blood levels are metabolized and lowered by healthy probiotic populations.  Probiotics are able to resist translocation, defined as the passage of pathogens from the GI tract to extraintestinal sites such as the mesenteric lymph node (MLN), spleen, liver, kidneys, and blood.


A high complex carbohydrate diet (vegetables, fruits, whole grains, legumes) encourages the proliferation of most probiotics, especially bifidobacteria. Nondi-gestible food factors that selectively stimulate the growth and activity of probiotics in the gut are referred to as “prebiotics”.

Prebiotics are plant cell-wall polysaccharides, hemicellulose, pectins, gums, and nondigestible oligosaccharides. The best example of a prebiotic is Fructooligosa-ccharides (FOS), sucrose molecules linked in sequence with fructose.  FOS are widely found naturally occurring in many vegetables, grains and fruits including Jerusalem artichokes, chicory, burdock, garlic, onions and the dahlia plant. In Japan, FOS are widely used as a sweetener. Some companies that market probiotics add FOS to enhance the potency of their product.  FOS are selectively fermented by most strains of bifidobacteria which will then grow at the expense of pathogenic bacteria such as clostridia and E. coli.

Adverse Effects

Probiotics are considered generally to be very safe and well tolerated in the usual dosages prescribed. Highly sensitive individuals have reported the occasional occurrence of indigestion (nausea, heartburn) which disappeared when the supplement was discontinued or the brand of probiotic was changed.  Very rare cases of liver abscesses due to L. acidophilus have been reported in cases of chronic pancreatitis undergoing surgery.

The Numbers Game

Do not be fooled by products advertising mega billion live organism capsules. More is not necessarily better and may even be dangerous. The safe and effective dosage for most people is 1 – 15 billion viable L. acidophilus, L. casei, or bifido bacteria organisms daily. Combinations of 3 or more species per capsule work best according to most studies.

Dosages in excess of 20 billion viable organisms can produce gut disturbances and are not recommended. Smaller amounts of viable organisms are usually sufficient for therapeutic effect. For example, studies indicate that a daily supplement of 1.5 billion colony forming units of L. sporogenes are adequate for all purposes.  The odd thing about this is that some supplement companies manufacture 40, 50 or even 70 billion live bacteria per capsule. Not only is this overkill and unsupported by the medical literature, it could also be dangerous for many people with sensitive digestive systems.

Probiotic Inhibitors

Probiotics are inhibited by high simple sugar intake, a refined diet, caffeine, alcohol, chlorine, fluoride, tobacco, prescription antibiotics, steroids, vaccinations and x-rays.  There is also some evidence that casein, a milk protein found in most commercially available dairy products, inhibits probiotic growth. The antibiotics found in conventional dairy products are also a factor in suppressing probiotics. So are the antibiotics in conventionally raised (non-organic) red meat, fish and some seafoods, especially of the farmed variety.

Probiotic Sources

Cultured dairy products like yogurt, acidophilus milk, buttermilk, sour cream, cottage cheese and kefir are the best known food sources of friendly bacteria.  Equally effective probiotic food sources include cultured/fermented vegetables (cabbage, turnips, eggplant, cucumbers, onions, squash, and carrots), and organic soy products like tempeh and miso.  Other, lesser known or used food sources of probiotics are sauerkraut and sourdough breads. Ideally, one could get a good supply of probiotics from one or more of these diverse foodstuffs.  If dietary sources are not easily available, supplemental probiotic powders and capsules are good alternatives. Choose a brand that has at least 3 different strains of friendly bacteria and between 6 – 15 billion live organisms.

Other Probiotic Myths

Many people believe that they don’t need to worry about taking a probiotic supplement if they eat yogurt. This is false because yogurt contains nothing that protects the friendly bacteria from being digested by stomach hydrochloric acid. Commercial yogurts are also high in added sugar (13 – 17 grams) and other harmful additives. A typical serving does not provide the bare minimum of 10 billion active bacteria required for probiotic effectiveness according to most studies.

There is a cult belief that Homeostatic soil organisms (HSOs) are safe and effective probiotics. These are usually much higher priced than your usual brand name products. HSOs originated in Japan and go by the names Bacillus subtilis and Bacillus licheniformis. Studies do indicate that they work for many people but the major problem with HSOs is that they can enter the bloodstreams of people who suffer from leaky gut syndrome or depressed immunity and cause a bloodstream infection called septicemia. This does not happen with lactobacilli or bifido bacteria unless the dose given is astronomically high.

Another myth is that one should not take probiotics when using prescription antibiotics. This is completely false because most antibiotics destroy both friendly and pathogenic bacteria and thereby produce an immune compromised state. The best strategy is to take probiotics on the same day as antibiotics, but at least 6 hours apart.  (Antibiotics will destroy the probiotics if they’re taken at the same time.) By taking the antibiotics and probiotics at different times, both the antibiotic and the probiotic do their jobs, with the probiotic making up for the damage caused by the antibiotic and preventing abnormal immunity while still allowing the antibiotics to kill the pathogens in the bloodstream or various tissues and organs.

Best Supplement Brands

There is no legitimate published research comparing the clinical efficacy of one brand of probiotics over others. is an excellent independent web site comparing the quality of various probiotic supplements. Studies claiming the efficacy of one particular brand are usually funded by the manufacturer of that brand. Before believing that an expensive prescription form of a probiotic brand is superior because it’s “evidence based” and covered by some drug plan, check to see who sponsored the study. Most of the studies published in the medical journals are funded by drug companies so, buyer beware. These are usually grossly over-priced and of insignificant benefit compared to the majority of health food store brands.

Since the intestinal micro-ecosystem typically carries up to 400 strains of bacteria, it makes sense to use a product that provides a broad spectrum of viable organisms combined with FOS.  Some suppliers claim that the probiotic strains can only work if given one at a time.  There is no evidence that this is true.  Single strain probiotics are indeed effective but, in most individuals, a brand with multiple strains works best.  Certain single strains do not have the near-magical properties that the advertising hype would lead one to believe. The best advice here is to consult the knowledge and experience of health care practitioners familiar with probiotics.


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Zoltan P. Rona, MD, MSc, offers consultations on nutrition and natural remedies in Thornhill. He has recently retired from medical practice as a Complementary and Alternative medical practitioner and now strictly offers nutritional consultations. He is the medical editor of The Encyclopedia of Natural Healing and has also published several Canadian bestselling books, including Vitamin D, The Sunshine Vitamin. To see more of Dr. Rona’s articles, visit: and for appointments, please call (905) 764-8700; office located at: 390 Steeles Ave. W., Unit 19, Thornhill, Ontario

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