Probiotics: Exploring the benefits of an already established relationship

Probiotics are live microorganisms, commonly bacteria, that live symbiotically within the digestive tract. They are often referred to as “good” bacteria and are part of our natural microflora. Evolutionarily speaking, humans and other animals have developed a symbiotic relationship with bacteria in the digestive tract because both organisms benefit from this connection. These bacteria live symbiotically within our digestive tract and confer health benefits to us, the host, by helping with digestion and absorption of nutrients, prevent invasion of pathogenic bacteria and help in the stimulation of the immune response. In exchange, the host provides a nutrient rich niche for the bacteria to live. Our natural microflora is established when we are born and has the ability to adapt as we age and as our diet, and other environmental factors, change. Although similar, the bacteria found within our digestive tract is unique amongst individuals. Therefore, it is no wonder why scientist would like to take advantage of this already established symbiotic relationship between humans and bacteria and turn it into probiotics.

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What are probiotics?

The World Health Organization defines probiotics as “Live microorganisms which when administered in adequate amounts confer a health benefit on the host”. Probiotics are not to be confused with prebiotics, which are the indigestible food substances that we can eat to selectively stimulate the growth of the microorganisms already present in our digestive tract. Unlike prebiotics, probiotics are living microorganisms that we can ingest in order to provide health benefits. Probiotics are often associated with common foods and health supplements because they are often present in foods such as yogurt, milk, juices and soy beverages. They are also present in dietary supplements and often used in health as a preventative medicine or in the maintenance of overall health.

What types of bacteria are “probiotical”?

The most common type of probiotics that are found in our food and dietary supplements are from the Lactobacillus (L.) and Bifidobacterium (B.) groups. Within these groups, there are many different species such as L. casei, L. gasseri, L. reuteri, L. acidophilus as well as B. bifidum, B. infantis, and B. breve. Before the addition of these probiotics to our food and supplements, safety tests are done to determine if the potential probiotic is safe for human consumption. Because probiotics are simply the administration of bacteria that are already present in your digestive tract, they are often well tolerated. Side effects are usually mild and are gastrointestinal in nature – such as gas or bloating – making it an attractive use in medicine.

What makes a good probiotic?

A probiotic must possess certain qualities in order for it to be effective. First, a probiotic needs to remain viable after it has passed through the highly acidic environment of the stomach. A probiotic has to reach the small intestine, the area where we absorb all of our nutrients from the food we eat, if it wants to confer its health benefits to the host. Second, the probiotic must be able to attach and colonize on the epithelial cells of the intestine. The action of a probiotic colonizing within the intestine acts as a protective measure against the colonization of pathogenic bacteria thereby preventing infections. Finally, it needs to confer its health benefits to the host. These benefits may be to prevent infection of pathogenic bacteria, to secrete substances that may stimulate immune responses, decrease the uptake of fats and cholesterol, or simply secrete molecules that have been shown to promote the health of specific organs in the body.

Probiotics in the prevention and treatment of disease.

Probiotics have already been shown to be helpful in the treatment of diseases, including acute and travellers diarrhea, irritable bowel syndrome, Crohn’s disease and ulcerative colitis. They have also been shown to be useful as having preventative effects for conditions such as skin eczema, vaginal yeast infections and urinary tract infections. Furthermore, probiotics have the ability to give your immune system a boost, thereby preventing or reducing the severities of colds and flu.

For example, when a person takes antibiotics to treat bacterial infections, those antibiotics destroy the “bad” infective bacteria that are invading your body, but they also damage the “good” bacteria that are a part of your natural microflora. As a result, these newly acquired spaces in your digestive tract, once occupied by “good” bacteria, are great places for opportunistic pathogens to invade, causing a secondary infection. The regular consumption of probiotics during antibiotic treatment can alleviate these post-antibiotic treatment infections and be used as a preventative medicine against secondary infection.

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Potential probiotical drug treatments.

Current research is working towards the development of the first probiotical drug. There are many research laboratories working with specific bacteria that can help in the treatment of specific diseases, such as cardiovascular disease. High levels of Low Density Lipoprotein (LDL) (“bad”) cholesterol and low levels of High Density Lipoprotein (HDL) (“good”) cholesterol, have been associated with cardiovascular disease. Current pharmaceutical medications work towards decreasing “bad” cholesterol and increasing “good” cholesterol in order to prevent cardiovascular disease. Specific probiotical species, such as the Lactobacillus and Bifidobacterium mentioned above, can secrete chemical substances that have been shown to lower “bad” and increase “good” cholesterol, making it a potential in the treatment of cardiovascular disease. Therefore, research is aiming to use probiotics as medications used in the treatment of specific diseases, such as cardiovascular disease.

When “good” bacteria go “bad”.

While the effects of probiotics can be beneficial, studies have also shown that administering a probiotic does not have a permanent effect as the probiotic is not able to colonize permanently. This means the continuous administration of probiotics may be necessary if a persistent effect is desired. Concerns have also been raised about the use of probiotics as medicines because they are living microoganisms that have the ability to change, adapt and mutate. Bacteria have the ability to exchange genetic material, which can mean that bacteria can transfer genes to one another. This can include genes that confer antimicrobial resistance, which is of great concern when it comes to the use of bacterial species in medicines. Bacterial mutations and genetic transfer may prove to be beneficial to the bacterial cell itself, but can also be detrimental to the host, as is the case with antibiotic resistant bacteria. In addition, probiotics are bacteria and therefore have the potential to cause infections, especially in high risk individuals such as children, elderly patients as well as immuno-compromised individuals (such as patients who are HIV positive and individuals who are on chemotherapy treatment). Although probiotics may be useful in the treatment of diseases, we cannot forget that bacteria are living systems that have the potential to change and adapt, making them unpredictable.

Conclusions

Probiotics have already been used in complementary and alternative medicine to help in the treatment or prevention of many diseases such as irritable bowel syndrome, ulcerative colitis, Chron’s diesease and urinary tract infections. Research is currently working towards creating the first probiotical drug to treat specific diseases such as cardiovascular disease. Probiotics are an attractive choice as they are often a bacterial type that already lives symbiotically in your digestive tract, therefore minimal side effects are experienced. As research continues identifying the probiotics that are present in the digestive tract, there will be more and more choices available for probiotical solutions as preventative medicines and in the treatment of disease. Keeping in mind the unpredictability of living micro-organisms, much research still needs to occur in order to determine safe and effective ways to manage health and disease with the use of probiotics.

References:

Doron S, Gorbach SL. Probiotics: their role in the treatment and prevention of disease. Expert Review of Anti-Infective Therapy. 2006; 4(2): 261–275.

Fuller R. Probiotics in human medicine. Digestive tract. 1991 Apr;32(4):439-42.

Nation Centre of Complimentary and Alternative Medicine. An introduction to probiotics. Available at http://nccam.nih.gov/health/probiotics/introduction.htm. Accessed July 24, 2011.

Ooi, LG and Liong MT. Cholesterol-lowering effects of probiotics and prebiotics: A review of in vivo and in vitro findings. Int. J. Mol. Sci. 2010; 11: 2499-2522.

Rastall RA. Bacteria in the digestive tract: friends and foes and how to alter the balance. J Nutr 2004; 134: 2022S-2026S.

World Health Organization. Guidelines for the Evaluation of Probiotics in Food. Available at http://www.who.int/foodsafety/fs_management/en/probiotic_guidelines.pdf. Accessed July 24, 2011.