Probiotics and the Human Microbiome

By Timothy Prentiss
Staff Writer
Kirkman Group, Inc

We are far less human than we might think. Though that statement may sound like pseudo-philosophy, it’s actually a biological fact. As odd as it might sound, the human body is made up of a large number of microorganisms that are not considered human cells. In fact most of the human body is non-human, the most reliable estimate currently being that human cells are outnumbered by non-human cells at a rate of about three to one (though some have estimated rates as high as ten to one). The sum of all of this non-human life in us and on us is known as the “ human microbiome.”

Most research on the microbiome has focused on gut flora–the portion of the microbiome that resides in our digestive tract. Correlations have been made between gut flora and a number of other conditions, both temporary and chronic—mental health issues,immune system strength2 and a variety of special needs conditions.3, 4  

It is not yet clear, however, what (if any) causal relationship exists. Does gut flora influence or even cause these conditions? Are the gut conditions and the mental (or other) conditions simply co-occurring, possibly both triggered by an unknown third variable? But whatever the relationship is exactly, research has shown repopulation of depleted gut flora can reduce the symptoms of certain chronic conditions, at least in mice.5

Gut flora both acts upon and is acted upon by the foods we consume. Certain diets, especially those lacking “live” foods like yogurt and other fermented products will lead to a depletion of healthy bacteria. Depletion of healthy gut bacteria can also lead to unhealthy bacteria flourishing. Eating live foods can help to repopulate the gut with healthy bacteria; one can also take a probiotic supplement.

Most probiotics sold commercially are members of one of two genera: lactobacillus and bifidobacterium. Of the two, lactobacillus is the more commonly available commercially. It occurs naturally in yogurt and various fermented foods such as sauerkraut. There are more than 50 known species of lactobacillus. Lactobacilli predominantly reside in the small intestine.

Bifidobacterium, though also important to adult gastrointestinal health, is particularly important in children. Like lactobacillus, it also naturally occurs in certain dairy products—several species having been found in various raw milk cheeses. So far, there are more than 30 species that have been discovered. Bifidobacteria predominantly reside in the large intestine.

In probiotic products offered by Kirkman®, there are ten species of probiotics included—either in combinations or as single-strain products.

Lactobacillus acidophilus

L. acidophilus is probably the most commonly used probiotic. It sets up residence in the mucosal membrane of the mouth, in the small intestine and in the genitourinary tract. It inhibits the growth of undesirable flora, aids in digestion and produces lactase enzymes (which help break down lactose). (Included in Kirkman’s Lactobacillus Acidophilus – Hypoallergenic product.)

Lactobacillus casei

L. casei resides in the mouth and in the membrane of the small intestine. It enhances the number of immunoglobulin A (IgA) producing cells,6 which play an important role in the mucosal immune system response. It has also been found to provide peptido-glycan,7 which stimulates phagocytosis by macrophages8—another important immune system process. (Included in Multi-Flora Spectrum™ and our entire Pro-Bio Gold™ line.)

Lactobacillus plantarum

L. plantarum is a lactic acid producing bacteria that has been shown to be particularly effective against certain hard-to-eradicate bacteria.10 (Included in Lactobacillus DuoMulti-Flora Spectrum and our entire Pro-Bio Gold™ line.)

Lactobacillus rhamnosus

L. rhamnosus resides in the small intestine, helping to crowd out undesirable flora. It also has been shown to increase production of IgA cells.11 (Included in Lactobacillus DuoPro-Culture Gold™Multi-Flora Spectrum and our entire Pro-Bio Gold™ line.)

Bifidobacterium bifidum

B. bifidum produces acetic and lactic acids in the digestive system. The resulting increase in acidity creates an environment that is inhospitable to undesirable flora. Like l. casei and l. rhamnosus, it also supports the immune system through an increase in IgA cells.12 (Included in Bifido Complex™ Advanced FormulaMulti-Flora Spectrum, and our entire Pro-Bio™ Gold line.)

Bifidobacterium breve

B. breve has been shown to be effective in colonizing the bowels of infants, resulting in fewer abnormal symptoms and improved weight gain.13 It also has a positive effect on the immune system.14 (Included in Bifido Complex™  Advanced Formula.)

 Bifidobacterium lactis

B. lactis aids in the crowding out of undesirable flora. It also enhances the immune system response of the intestinal mucosa.15 It has also been shown to be helpful to infants with diarrhea.16 (Included in Bifido Complex™  Advanced Formula and Super Pro-Bio™  75 Billion.

 Streptococcus thermophilus

While bifidobacterium and lactobacillus are “resident” bacteria, meaning they colonize and reproduce inside the body, s. thermophilus is “transient,” meaning it passes through the body.  S. thermophiles produces the lactase enzyme, which is necessary for the digestion of lactose. It also produces lactic acid, which helps create an environment inhospitable to undesirable flora.17 (Included in Multi-Flora Spectrum and our entire Pro-Bio™ Gold line.)

Kirkman’s probiotic products include our proprietary and best-selling probiotic, Pro-Bio Gold™. Click here for a complete list of Kirkman’s probiotic products.


1. Venosa, A. Depression not just a mental illness; it’s a systemic disease that affects the entire body, Medical Daily. Mar 10, 2016

 2. Purchiaroni F, Tortora A, Gabrielli M, Bertucci F, Gigante G, Ianiro G, Ojetti V, Scarpellini E, Gasbarrini A. The role of intestinal microbiota and the immune system. Eur Rev Med Pharmacol Sci. 2013 Feb;17(3):323-33.

 3. Krajmalnik-Brown R, Lozupone C, Kang D-W, Adams JB. doi:10.3402/mehd.v26.26914.

 4. Eat more yogurt! Low levels of healthy gut bacteria could be the cause of mental health issues such as ‘anxiety and schizophrenia’, Daily Mail, 12 Sept. 2013

 5. Hsiao, E. Y. et alCell (2013). 

This entry was posted in All, Gastrointestinal Health, Immune System, Microbiome, Probiotics and tagged , . Bookmark the permalink.

One Response to Probiotics and the Human Microbiome

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