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This is an up to date and thorough presentation about probiotics in general, and our very high potency probiotic dietary supplements in particular. It shows how and why they work, and discusses the health benefits likely to occur from their consumption.

WHAT ARE PROBIOTICS?

The word probiotic is derived from the Greek meaning "for life".  Probiotics are "mono- or mixed cultures of live microorganisms which, when applied to animal or man, beneficially affect the host by improving the properties of the indigenous microflora"(1). The common terms for probiotics are "friendly", "beneficial" or "healthy" bacteria.

Probiotic bacteria are generally, though not exclusively, lactic acid bacteria and include Lactobacillus acidophilus, L. casei, L. bulgaricus, L. plantarum , L. salivarius, L. rhamnosus, L. reuteri, Bifidobacterium bifidum, B. longum, B. infantis and S. thermophilus. They are used in the production of yogurt, various fermented milk products and dietary supplements.

LACTOBACILLI AND BIFIDOBACTERIA

Lactobacilli and Bifidobacteria are Gram-positive lactic acid-producing bacteria that constitute a major part of the normal intestinal microflora in humans and animals.  They play an important role in resistance to colonization against exogenous, potentially pathogenic organisms.

Lactobacilli:  Lactobacilli are Gram-positive, non-spore forming rods or coccobacilli.  They have complex nutritional requirements and are strictly fermentative, aerotolerant or anaerobic, aciduric or acidophilic.  Lactobacilli are found in a variety of habitats where rich, carbohydrate-containing substrates are available, such as human and animal mucosal membranes, on plants or material of plant origin, sewage and fermenting or spoiling food (8).

Bifidobacteria:  Bifidobacteria constitute a major part of the normal intestinal microflora in humans throughout life.  They appear in the stools a few days after birth and increase in number thereafter.  The number of bifidobacteria in the colon of adults is 10⁸ - 10¹¹ CFU/gram, but this number decreases with age.  Also demographic differences affest the number and species of bifidobacteria.  Bifidobacteria are nonmotile, nonsporulating Gram-positive rods with varying appearance.  Most strains are strictly anaerobic.  B. longum may be considered as the most common species of bifidobacteria, being found both in infant and adult feces.  This species is closely related to B. infantis, which often leads to identification problems (8).

BALANCING THE INTESTINAL ECOSYSTEM

The condition and function of the gastrointestinal tract is essential to our well being. After the respiratory tract, the GI tract constitutes the second largest body surface area, comparable in size to a tennis court. During a normal life time about 60 tons of food pass through this canal.

The human intestinal microflora is highly important to the host for several reasons.  Firstly, microflora benefits the host by increasing resistance to new colonization as well as by protecting against the overgrowth of already-present potentially pathogenic organisms.  Another function important to the host is the high metabolic activity of the intestinal flora.  The extent of this activity has been claimed to be similar to that of the liver.  Administration of antimicrobial agents is the most common cause of disruption of the balance of the normal microflora and leads to decreased resistance to colonization and to alterations in the metabolic activities of the intestinal flora.

For thousands of years microbial cultures have been used to ferment foods and prepare alcoholic beverages.  In Genesis references are made to the preparation of fermented milk. Microorganisms have been tested in the 19^th century to prevent and cure diseases, and have been added to domestic animal feed to enhance growth. However, it is probably from the work of the Russian Nobel Prize Laureate Elie Metchnikoff in 1908 that the first scientific assessments of probiotics were made.  He first hypothesized that a high concentration of lactobacilli in intestinal flora were important for health and longevity in humans.  Indeed, we now know that the gut flora plays an important role in health: stimulating the immune system, protecting the host from invading bacteria and viruses, aiding digestion and assimilation of food. Yet, the importance of these bacteria in the GI tract has been neglected for a long time, while the focus was merely placed on enteric pathogens and other factors leading to gastrointestinal "disorders".