A thorough explanation of probiotics & prebiotics

Probiotics don’t have to be confusing. Strip away some of the difficult language of microbes and along with prebiotics, their partners in health, probiotics come into focus.

Here’s what you need to know:

Probiotic literally means “pro-life”

Probiotics are “live micro-organisms that when administered in adequate amounts confer a health benefit on the host” (World Health Organization, 2001). Probiotics can restore intestinal microflora which often become unbalanced due to illness, stress, age, traveling or use of medication such as antibiotics. Note that effects are strain specific and so are not assumed for the spectrum of probiotics.

Probiotics spur growth of new colonies

Antibiotics do the opposite; they stifle or kill microbes. Probiotics are primarily bacteria but some species of yeast, such as Saccharomyces, are equally helpful. Most probiotic organisms belong to the lactobacillus and bifidobacterium genera. However, there are many genera, species, and strains of bacteria that bloom in the human gastrointestinal tract at any one time.

The Lactobacillus genus

Lactobacillus is a celebrity among probiotic bacteria. This genus contains about 80 recognized species, with the most well-known being Lactobacillus acidophilus. The name “Lactobacillus” is broken down into “lacto,” derived from “lactic” acid, and “bacillus,” meaning rod-shaped. Thus, lactobacillus species are rod-shaped bacteria that produce lactic acid from fermentable sugars such as glucose, fructose, lactose and/or galactose. The major by-products of lactobacilli fermentation are lactic and acetic acids.

The Bifidobacterium genus

Bifidobacterium is the most abundant genus of good bacteria in the human gastro-intestinal tract. The “bifido” part of the term “bifidobacteria” comes from “bifidus,” meaning “split in two, separated by a cleft.” Thus, bifidobacteria can often be identified by their Y-shaped or bifid structure. However, bifidobacteria also exist in V- or X-shaped forms, and can be found in more rounded shapes as well. The major by-products of bifidobacteria fermentation are lactic, acetic, and butyric acids; additionally succinic acid can also be produced by some strains of bifidobacteria.

Nomenclature or “what’s in a name?”

Probiotic bacteria are strain dependent, not species dependent–an important distinction. A strain is a type of a bacterial species, similar as to the example below:

Bacterial group = German car = lactic acid bacteria Bacterial genus = Volkswagen = Lactobacillus Bacterial species = VW Golf = Lactobacillus acidophilus Bacterial strain = VW Golf 1.4 D = Lb. acidophilus LC1

Everybody knows that a Volkswagen Golf 1.4 D has other characteristics than a Volkswagen Golf 2.0i turbo, but you can’t see the difference on the outside.

The same is true for bacteria; they all look the same, but the biological characteristics (‘the engine’) are different. Hence, claims on health effects of a certain probiotic are only valid for that specific strain, not species.

We are outnumbered.

As many as 1000 and possibly many more different species of bacteria live inside us. When added together, our microbes have ten times the number of cells we have. Their numbers suggest that we, perhaps, exist as their guests.

These colonies of bacteria set up shop along the gastrointestinal tract, the internal highway that extends from the mouth to the anus. When they do a good job, we call them “pro-biotic”.

Probiotics operate in several ways, including:

  • competing with pathogens
  • stimulating both mucosal and systemic immunity
  • metabolizing hormones and carcinogens
  • synthesizing vitamins K, pantothenic acid, B6 and biotin, and synthesizing short-chain fatty acids.

There are doubtless other mechanisms which have not yet been identified.

Probiotics need to eat, which is where prebiotics enter the picture. Fermentable carbohydrates such as dietary fiber, oligosaccharides and non-absorbed sugars nourish probiotics. A high sugar, high fat, low fiber diet feeds the pathogenic or bad bacteria.

Acidity is also important: even a slightly acidic scene in the colon kills bad bacteria and enables the good ones to shine. But a high meat diet, high fat intake, alcohol, stress, antibiotics and other medications clear the stage for harmful bacteria.

Benefits of probiotics

Probiotics sometimes seem too good to be true. Believe it.

Clinical studies show that probiotics offer numerous health benefits. Some of the scientifically established health effects are:

  • Reduction in the occurrence and duration of rotavirus diarrhea.
  • Reduction in duration of antibiotic-associated diarrhea.
  • Alleviation of symptoms of lactose intolerance.
  • Alleviation of symptoms of food and skin allergies in children.
  • Reduction of recurrent ear and bladder infections.
  • Reducing incidence and/or duration of bacterial vaginosis.
  • Improvement of halitosis.

Some of the common probiotics enhancing health belong to the following species: (Please note that not all within one species can be regarded as probiotics).

Probiotics support the gut flora balance and so the strongest evidence for the clinical effectiveness of probiotics has been in the treatment and prevention of acute diarrhea and antibiotic-induced diarrhea. Recent research also confirms roles for probiotics in the prevention of traveler’s diarrhea, Clostridium difficile infection and irritable bowel syndrome.

But probiotics don’t only act close to home.

They also impact the immune system, a network of white blood cells racing through blood and lymph. Beneficial bacteria also enhance vitamin, mineral and enzyme metabolism, which strengthens the host in multiple ways.

Through these channels, probiotics are thought to influence a whole field of diseases and conditions: asthma, allergies, dental caries, ulcers, hepatic encephalopathy, urinary tract infections, vulvovaginal candidiasis, dermatitis, inflammatory bowel diseases, type 1 diabetes mellitus, heart disease, obesity and cancers.

An impressive job description, indeed. Now if we just knew which strains exert which effect, we would be in business. As it is now, the considerable research is underway to get us there.

New molecular techniques that give accurate pictures of the flora are resulting in better science of the mechanisms of each strain.

Making probiotics both fascinating yet challenging is that different strains of bacteria bestow different health benefits.

The clinical use of probiotics is controversial. In 2007, a Yale University workshop came up with some recommendations: Ratings ranged from an “A” rating where evidence was strongest, with plenty of randomized, controlled studies to a “B” rating –where evidence was good but hampered either by negative studies or a limited number of studies- to a “C” rating which fell short of receiving stronger ratings because of the size of reported patient studies, yet were still significant.

An “A” rating for probiotics was given for their reach in acute childhood diarrhea, prevention of antibiotic-associated diarrhea, prevention and maintenance of remission in pouchitis, and in treatment and prevention of atopic eczema associated with cow’s milk allergy.

“B” ratings went to treatment of inflammatory bowel disease and irritable bowel syndrome.

But plenty of new studies are adding to those. The IPA Disease Library here on this site is a convenient and a comprehensive guide to probiotic benefits.

In addition, each month we will spotlight one disease or disorder in more detail and examine its link to probiotics. Expect only research from the source and expert opinion.

Clearly, probiotics are valuable components of a healthy organism. Their inclusion in a balanced diet, whether through food or supplements, is crucial for the health and well-being of the host.