The traditional meaning of the word “probiotics” is “live microorganisms that may confer a health benefit on the host.”[1] A far more helpful definition is probiotics are microbes that help a person stay in optimum health. After growing up within a culture that encourages the usage of anti-bacterial cleaning soap, alcohol-containing hand gel and powerful antibiotics, this could feel bewildering. How does something, which is regarded for some time to be harmful, help with one’s health?

The First Probiotics

Yoghurt and Soy Yoghurt RedCredit: By Feuerrabe (Own work) [CC-BY-3.0-de], via Wikimedia CommonsThe very first report showing that microbes can improve the overall health of humans was in 1907 by Elie Metchnikoff. Dr. Metchnikoff found a correlation amongst populations eating yogurt with an increased life span[1]. A more colorful early tale describing the usefulness of probiotics was the discovery of Bacillus subtilis by Nazi medics. Searching for a treatment for dysentery, they uncovered that neighboring Arabs ingested fresh camel dung to protect themselves from the sickness. Examination of the dung showed that B. subtilis was the protective agent[2]

Microbes Are All Around

Eating camel dung is not what the majority of us would consider a smart behavior. On the other hand, a lot of us do eat yogurt, kefir, cheese, sauerkraut, and other fermented foods that are jam-packed with microorganisms. It’s essential to understand that the environment is anything but sterile. It’s actually exploding with microbes. This can also be said for our bodies as well. We are breeding grounds for microorganisms providing perfect living conditions for them. We deliver warmth and nourishment by shedding skin and ingesting food. The colon, one of the most microbe-rich regions within the body, harbors trillions of microorganisms, and these microorganisms make up more than 60% of the dry mass of your feces. More than one thousand different species inhabit our bodies, and this community is, nowadays, called the “microbiota.” Other terms for the intestinal microbiotia include “intestinal flora” or “commensal microbes.”

How Do They Do Their Job?

It is proposed that there are three major modes of action for probiotics[1]:

  • Probiotics can make it trickier for pathogenic microbes to survive the microenvironments of the body. They do they by competing for resources, changing local pH and producing substances that can kill other bacteria.
  • Probiotics can interact with the non-immune cells of your body and make them raise their defenses in against invading microorganisms. An example would be inducing the cells lining the intestinal wall to produce anti-microbial peptides. 
  • Probiotics can greatly enhance the function on immune system cells. Depending on the probiotic, pro-inflammatory as well as anti-inflammatory responses can be induced. 

Harmful Bacteria vs. Good Bacteria

LactobacillusCredit: Riccardoariotti microscopio Olympus 1000 x, colorazione Diff Quik via Wikimedia CommonsIn general, our commensals are harmless. Nonetheless, there are circumstances where they can cause problems. These problems occur when they are permitted to penetrate the interior confines of our bodies where they do not ordinarily reside. When this happens, "sepsis" can occur. Sepsis is when our bodies produce such a strong immune response that it interferes with the normal functioning of the body. If not treated, it can be life threatening[3]. This can happen during an injury or when one has a compromised immune system. The immune system functions as a police department and controls the bacterial masses. It stops their entrance into restricted parts of the body and controls their overgrowth. Sepsis, on the other hand, is similar to using an atom bomb - everything gets destroyed in the persuit of the enemy.

In general, however, normal flora will never cause problems. There are, however, species of microorganisms that are famous for being bad, and these pathogenic bacteria have unique characteristics that normal intestinal flora do not have. Examples are Escherichia coli O157:H7 and Salmonella species, which induce food poisoning. Other examples are Clostridium tetani, which causes tetanus and Klebsiella pneumoniae, which causes pneumonia. These microorganisms have what are called, "virulence factors." Examples of virulence factors are the production of toxic compounds or the power to adhere to tissues internally. 

Probiotics in Action

Besides the story of B. subtilis[2] in curing dysentery, you will find quite a few disorders where probiotics are likely to help. They can be pretty effective for infectious diarrhea, such as rotavirus-associated diarrhea and Clostridium difficile-related diarrhea. They are also helpful in antibiotic-induced diarrhea, which is caused when antibiotics destroy the microbial balance in the intestines. There is also evidence that they work for vaginal yeast infections. Other disorders where they are helpful include constipation, irritable bowel syndrome, eczema and the cold[3]

Probiotic Safety

While fermented foods containing beneficial bacteria, like yogurt, have been consumed for generations, caution is still advised with bacterial supplements. Probiotic supplements are much different than yogurt or other fermented foods. Supplements contain high doses of purified microorganisms and some fillers (very often lactose). Yogurt, in contrast, contains many other nutrients like fat, protein and sugar, which can have the ability to alter how the microorganisms interact with your body. In addition, some investigators have proven that the inflammatory status of an individual person influences probiotic function. For instance, people with chronic inflammations or a weakened immune system may not react in the same way to probiotics as a healthy person[4]. Therefore, it is always wise to speak to a health practitioner or nutritionist and first assess your personal health before engaging in daily regimen of potent probiotics.