Although the main functions of the digestive system were once believed to include little beyond the breakdown of food into usable energy for the body and elimination of waste, the digestive tract is also home to 100 trillion microorganisms, known as the gut flora. The majority of these microorganisms are bacteria, with a small percentage consisting of fungi and protozoa. The functions of the gut flora are complex enough to resemble those of an organ, leading some researchers to refer to the gut flora as a “forgotten organ”. Indeed, the gut flora plays a number of roles so vital to the human body that if the gut were to be sterilized, long-term survival would be unlikely.
Types of Gut Flora
There are three main categories of microorganisms found in the gut:
1.) Essential Flora: This is the “friendly” bacteria that is found in the gut. In the healthy individual, essential flora dominates and controls other types of less desirable microorganisms. When functioning normally, this type of flora is responsible for conducting numerous roles that keep the body healthy.
2.) Opportunistic Flora: This group of microbes is found in the gut in limited numbers that are strictly controlled by the essential flora in the healthy individual. This type of flora is capable of causing disease if the essential flora becomes compromised and is unable to control the growth and numbers of opportunistic flora.
3.) Transitional Flora: These are various microorganisms that are introduced into the body through eating and drinking. When the essential flora is healthy and functioning normally, this type of flora will pass through the digestive track without causing harm. However, if the essential flora is damaged, this group of microbes can cause disease.
Roles of the Essential Gut Flora
Beyond controlling the population of opportunistic and transitional flora, essential gut flora plays an active role in the normal digestion and absorption of food by producing enzymes that aid in the process of breaking down proteins, carbohydrates, and fats. It also aids in the transportation of minerals, vitamins, water, and other nutrients through the gut wall into the bloodstream for use by the body. Certain types of essential flora are capable of manufacturing nutrients such as vitamins K2, B1, B2, B3 B6, B12, folic acid, pantothenic acid, and various amino acids. In addition to producing these nutrients to be used directly by the body, the essential flora provides nourishment to the cells of the intestinal wall that have primary responsibility for digesting and absorbing food. When the essential gut flora are compromised and not functioning normally, it is common for the individual to become malnourished and have multiple nutrient deficiencies and food intolerances.
In the last decade or so, the importance of the gut flora to immune function, overall health, and disease has become an emerging area of focus. Although there is still much to be learned about the role of gut flora in immune function, it is becoming increasingly clear that disease (and health) really does begin in the gut! Studies have shown that the gut flora has a profound influence on the development and maturation of the immune system after birth (Bouskra et al., 2008; Macpherson & Harris, 2004). In addition, it has been estimated that approximately 80 -85% of the immune system is located in the gut.
In the healthy individual, the essential gut flora forms a bacterial layer that covers the entire digestive track. This bacterial layer acts as a physical barrier to protect against transitional flora , viruses, parasites, toxins, and undigested food particles. The gut flora produces acids that lower the pH of the gut wall and make it undesirable for microbes that cause disease. The essential flora also has the ability to neutralize many toxins and inactivate carcinogens (substances known to cause cancer). It also plays a direct role in suppressing the processes by which cancer cells are known to develop and grow.
The essential flora has a direct effect on important immune functions because it is responsible for stimulating the tissues of the lymph system that are located in the gut wall to produce lymphocytes, a type of white blood cell that fights infections. The lymphocytes then produce immunoglobulins, which are antibodies formed in response to contact with foreign substances (viruses, bacteria, fungi, etc). The immunoglobulins destroy and inactivate invading substances that enter the body through food and drink. The essential flora also has a direct impact on the function and/or production of other many other cells of the immune system. When the essential flora is damaged, immune function is affected not only in the gut, but systemically as well (throughout the entire body). Specific to autoimmune disease, essential gut flora plays an important role in the development of regulatory T cells, a critical component of the immune system. The types, number, and balance of regulatory T cells are directly influenced by the essential gut flora. The dysfunction of the regulation of different types of regulatory T cells (an imbalance in certain kinds of T cells) is responsible for the development of autoimmune disease.
A broader explanation of how the gut flora influences immune function is by understanding the balance between the two arms of the adaptive immune response, known as Th1 and Th2 immunity. In general, the role of Th1 immunity is to fight infections in the skin, mucous membranes, and cells. When the essential flora is damaged, the production and function of Th1 cells becomes impaired, allowing more invaders into the body. The body responds by overcompensating with a Th2 response. The overactive Th2 response then predisposes the individual to allergic-type reactions, chronic inflammation, and autoimmunity. Healthy essential gut flora is the key to keeping these arms of the adaptive immune system in balance, thus preventing disease.
References:
Campbell-McBride, N. (2010). Gut and psychology syndrome. Cambridge, United Kingdom: Medinform.
Important information! Thank you.
Thanks so much for stopping by! I’m glad you found it useful.
Reblogged this on My Cranky Gut and commented:
Excellent run-down of gut flora, exploring its types, its role in immune and systemic health, and how it all works to keep us healthy (or in some cases, unhealthy!).
Thank you for reblogging this!
You’re very welcome… thanks for posting it in the first place!
You’re so cool. I posted this on a Facebook group for IBD bloggers.
Thank you!!! I appreciate your support! Thanks so much for reading.
Is it “normal” for yeast/fungi to be present in the intenstines? And, if so, what can you do if there is “too much”? And, why would a person have parasites, yeast/fungi, and h.pylori all at once in the gut? And is it repairable? Thank you.
Hi Marie Ann! Yes, it is normal for yeast/fungi to be present in the gut. Yeast is part of the normal gut flora, although it is normally present in a much smaller percentage than bacteria. The essential bacteria usually keep the yeast in check. But when the gut flora becomes imbalanced, certain strains of yeast may become uncontrolled and allowed to multiply freely, which can lead to many problems in the body. A common yeast overgrowth is due to Candida albicans. Treating yeast overgrowth naturally involves several lifestyle and dietary changes, as well as supplementation in some cases. For severe cases that are associated with certain medical diagnoses, prescription anti-fungals may be necessary. However, anyone that suspects Candida overgrowth should also make lifestyle changes if they want to prevent the overgrowth from reoccuring. Dietary changes are a big part of that- eliminating processed sugars and foods, grains, legumes, and dairy, all of which contribute to the overgrowth. Fermented foods or supplementing with probiotics would be helpful, as would adding extra coconut oil into your diet. Certain medications are also known to contribute to Candida overgrowth- hormonal birth control pills, steroids, and antibiotics. If you can reduce the use of these medications (under a doctor’s supervision), it can be helpful in stopping the overgrowth cycle. Some people may also require the use of natural herbs and supplements to help fight the Candida overgrowth.
As far as the H. pylori, that is a subject in and of itself and it would be difficult to answer briefly and without knowing more information about your health concerns. About half of the world’s population carries H. pylori, but most are unaware of it because it hasn’t led to any health problems. If someone is having GI symptoms that leads a doctor to test for it, conventional medicine would then treat the H. pylori infection with antibiotics. Many alternative health practitioners believe that H. pylori may result from decreased stomach acid, and indeed, many of the GI diseases caused by H. pylori are actually associated with low stomach acid, rather than too much acid, as it is commonly believed.
If someone had parasites, yeast overgrowth, and H. pylori, I would venture to guess that their gut bacteria is imbalanced and they are also having issues with carbohydrate digestion (to summarize it briefly–this would be a lot to get into, but please contact me for more details). It is “repairable”, but it would require major lifestyle changes and a great deal of time to heal properly. I hope this helps!
Thank you. Do you know of anyone who has tried a fecal transplant for IBD? 2011 research at http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2036.2011.04737.x/abstract
Also have most people with IBD been test for their MAP levels?
Thank yo again
Hello! Thanks for stopping by! I don’t personally know of anyone or have had any patients that have undergone a fecal transplant for IBD. But the research looks very promising and I’ve read several case studies of individuals that have undergone fecal transplant and did quite well (went into remission). As far as testing MAP levels, that is not a standard of care or a routine test that would be performed for people with IBD. There have been some studies looking at the prevalence of MAP infection in IBD patients, but in general, this research has not translated to change in treatment of IBD. I hope this helps! Please let me know if you have any questions.
I only mention MAP because research apparently says that patients with CD have high concentrations of MAP to the tune of 92% of CD patients when compared with UC patients or non IBD patients. Also there was a combo antibiotic see http://beatingcrohns.blogspot.com/2009/09/myoconda-anti-biotic-kills-map-as.html that was going to address this. I am not sure where that stands. Anyway some people also are having difficulty getting diagnosed properly between UC and CD even though treatment may be the same. I am just trying to understand MAP and its relationship to CD in treatment and being properly diagnosed. Thanks.
Some studies show lower percentages of MAP. There are some that believe it may be one of the causative factors, but not the only one. The clinical trials in the US for the antibiotic in the link were stopped by the pharmaceutical company- I’m not sure of the reasons why. There is no easy or reliable way of culturing MAP (to determine that someone has it) and that is why it is not a factor in diagnosis or treatment. There are *a few* doctors out there that will treat MAP on the basis of elimination (very severe cases of Crohn’s that are not responding to other treatment). However, this is not routine treatment and it would probably be incredibly difficult to come across a physician who would agree to do it. Because MAP is difficult to culture, they aren’t entirely sure which antibiotics are the most effective. MAP is also very difficult to treat, since it may now be resistant to many antibiotics. Treatment involves being on very high doses of heavy duty antibiotics for a minimum of 24 months. Check out this interview with Dr. Borody, one of the physicians that has a special protocol for treating MAP: http://www.crohns.org/treatment/borody.htm.