By: Eryn O’Connell (ND Candidate 2016)

Did you know our bodies are home to a numerous and diverse population of microorganisms that are invisible to the naked eye, and our coexistence with these tiny creatures provides an essential foundation for our health and well-being? Many species of bacteria, fungi, and archaea cover all aspects of our bodies including our skin, ears, nose, eyes, mouth, digestive and urinary tracts. In fact, these microscopic organisms outnumber our own cells by 10:1!

This is an example of a symbiotic relationship in which the microorganisms and the human host benefit from one another. Our bodies provide a home and food source for these small organisms and in return, they help our bodies digest our food, create new nutrients, and are a key piece of the immune system thereby protecting us from potentially harmful organisms that cause illness.5 The process of colonization by these beneficial organisms begins at birth as we transition from the sterile womb to the outside world. It is this introduction that allows our immune system to organize itself through experience, just like the brain.5

One way to achieve the health benefits of these lovely little creatures is to supplement with prebiotics and probiotics. Prebiotics are found in dietary sources of fiber and indigestible carbohydrates and their role is to encourage the growth and activity of beneficial bacteria. The word probiotic originates from the Latin pro and biota meaning “for life.” According to the World Health Organization, probiotics are defined as live microorganisms, which when administered in adequate amounts bestow health benefits to the host.6

Probiotics are also found in many dietary forms such as yogurt and fermented or fortified milk products (kefir), however their potency is largely determined the number and viability of organisms contained within the product. It is important to note that not all probiotic supplements are created equal and their efficacy depends heavily on the quality of the supplement.1 Commonly, you will find species of LactobacillusBifidobacterium, and Sacchromyces boulardii within various supplements. Generally, these supplements are deemed as safe for healthy children and adults. Digestive disturbances are the most common side effect of probiotics, however those with compromised immune systems may carry a greater risk with supplementation of these products.

Probiotics achieve their health benefits through a variety of mechanisms, many of which are just starting to be understood through advances in modern medicine. Although the exact mechanisms are not well understood, it is believed they contribute to human health through four general benefits which will be described below.4 First of all, these  commensal or beneficial microorganisms who find a home on our bodies compete for space and food sources with potentially harmful organisms thereby preventing our exposure to illness. Secondly, these beneficial organisms provide a protective barrier in our digestive tracts thereby preventing harmful organisms from entering our body and inducing a systemic immune response. In fact, the immune system found in our gut is thought to be the largest immune “organ” in humans!6 Additionally, probiotics have been shown to decrease inflammation throughout the body as they help to facilitate communication between cells that lead to inflammatory or anti-inflammatory signals. Finally, it is believed that probiotics may play a role in the perception of pain.

The use of probiotics has been shown to have profound effects on the immune system, digestive and urinary systems and in the prevention of eczema. The use of probiotics is most well studied in Irritable Bowel Disease (IBD) which includes Crohn’s disease and ulcerative colitis.4 Additionally, probiotics have been shown to be effective in antibiotic related and infectious diarrhea, especially among children by decreasing the severity and duration of diarrhea. A large study published in 2015 showed probiotics to be more effective than placebo in reducing the duration of upper respiratory infections (URI’s) while also decreasing the need for antibiotic use and cold-related school absences.3

Probiotics containing lactobacillus have been shown to be beneficial in the prevention of urogenital conditions such as vaginal yeast infections, bacterial vaginosis and urinary tract infections (UTI’s). Lactobacillus is naturally present in the urogenital and reproductive regions and helps to create an acidic environment that is inhospitable to many organisms that cause dis-ease.

Finally, the World Allergy Organization recommends the use of probiotics in pregnant and nursing women whose children are deemed at high risk for the development of eczema based on environmental factors and family history. Interesting to note, probiotics have demonstrated a preventative effect in the development of allergies. Since so many children experience the “allergic triad” of asthma, allergies, and atopic disease such as eczema, probiotics can have a great impact on their health and well-being thereby providing a foundation which encourages a healthy and effective immune system.

In summary, our bodies are home to a diverse ecosystem of microscopic organisms and it is this diversity that allows for the most benefit to human health. In addition to a balanced diet, regular physical activity, and a supportive community, regular probiotic use can have a profound impact on our health. Talk with your doctor today to see which probiotics are right for you!

For more information and research news about probiotics:



  1. Berman, Sheryl, and Diane Spicer. “Safety and Reliability of Lactobacillus Supplements in Seattle, Washington (A Pilot Study).” IJAM The Internet Journal of Alternative Medicine 1.2 (2003). Web. 24 Feb. 2016.
  2. Fiocchi, A., Pawankar, R., Cuello-Garcia, C., Ahn, K., Al-Hammadi, S., Agarwal, A., … Schünemann, H.J. (2015). World Allergy Organization-McMaster University Guidelines for Allergic Disease Prevention (GLAD-P): Probiotics. World Allergy Organization Journal8(1), 4. doi:10.1186/s40413-015-0055-2
  3. Hao, Q., Dong Bi, R., & Wu, T. (2015). Probiotics for preventing acute upper respiratory tract infections. Cochrane Database of Systematic Reviews, (2). doi:10.1002/14651858.CD006895.pub3
  4. Sartor, R. Balfour, Thomas J. Lamont, and Silpa Grover. “Probiotics for Gastrointestinal Diseases.” UpToDate. UpToDate, 24 Aug. 2015. Web. 24 Feb. 2016.
  5. Katz, Sandor Ellix. Wild Fermentation: The Flavor, Nutrition, and Craft of Live-culture Foods. White River Junction, VT: Chelsea Green Pub., 2003. Print.
  6. West, Christina, Susan Prescott, Scott H. Sicherer, and Elizabeth TePas. “Prebiotics and Probiotics for Prevention of Allergic Disease.” UptToDate. UpToDate, 20 Oct. 2015. Web. 24 Feb. 2016.