The Road to Health is Paved with Good Intestines #6: The Large Intestine and Its Microbial Inhabitants.

In my last blog post, we made our way through the 22 feet of the small intestine. Once what has remained of our food completes that journey, it goes through a gate called the illeocecal valve and finds its way into the large intestine. The large intestine is only about 5 feet long but the diameter of the tube is quite a bit larger than that of the small intestine, thus its name.

By the time the food remains make it to the large intestine, our own digestion of it has completed. This does not mean that digestion is over though. The 5 pounds of bacteria that inhabit the large intestine are happy to feed upon whatever is left. They ferment carbohydrates that you were not able to digest and in doing so produce b-vitamins such as biotin, vitamin K, and short chain fatty acids that serve as an energy source not only for the cells of the intestine but for the rest of the body as well. Short chain fatty acids also help with the repair of cells in the large intestine and provide defense against colon cancer and inflammation in the large intestine.

In addition to the nutrients they synthesize the trillions of bacteria in your colon support optimal immune function, decrease allergic response, protect us from potentially harmful bacteria, enhance detoxification, and maintain optimal bowel transit time. In addition there is evidence that a healthy population of gastrointestinal bacteria can help in maintaining ideal cholesterol levels and optimal body composition as well as preventing against autoimmune conditions and certain forms of cancer. There is even emerging evidence that the bacteria in your gut can effect whether you feel anxious or calm.

Not all bacteria that we come in contact with are friendly and health promoting. If we consume food that contains salmonella, shigella, or certain strains of E coli we can become quite ill. In addition to these acute pathogens, there are some bacteria, yeast, and parasites that take up residence in our gastrointestinal tract that can make it less conducive to the growth of the good bacteria. They can cause unpleasant gastrointestinal symptoms such as diarrhea, constipation, increased gas production and intestinal cramping. They can make us more susceptible to developing food allergies and autoimmune diseases. They can also produce waste products that can cause inflammation, decrease brain function, cause muscle aches, and affect our mood.

Most things that we put into our mouths are covered with bacteria. Our immune system, a healthy population of good bacteria, and adequate production of stomach acid typically render them harmless. However, if stomach acid production is suppressed due to antacid or other acid blocking medication (see blog #4 for more details) , or if the immune function is depressed due to stress or poor diet, or if the population of good bacteria have been depleted, these unfriendly bacteria can flourish and make our lives miserable.

Recent evidence suggests that the overall makeup of the bacteria in your gut is established by the age of three. Exposure to bacteria through vaginal birth and breast feeding seem to have the major influences on how this community develops. While we can’t go back and change what occurred before we were three, some things that you can do to help foster a healthy population of bacteria includes:

“Eat food, mostly plants, not too much”. This quote is from Michael Pollan’s work, In Defense of Food, and its wisdom holds true for creating a healthy microflora population as well. The fibers and other polysachharides in plant foods serve as the prime food supply for our bacteria. The thing that we can’t digest, they do. People consuming a diet high in plant foods and lower in animal foods seem to have a greater biodiversity of gut bacteria.

Limit intake of processed foods. Processed foods tend to be void of the polysaccharides and fibers that feed our gut bacteria. Foods high in refined carbohydrates and sugars seem to feed less beneficial species of bacteria as well as encouraging the overgrowth of yeast species. Processed foods can also contain chemical compounds that can inhibit the growth of our gut bacteria and create a less hospitable environment for them to grow in.

Eat more fermented foods. Naturally fermented foods such as sauerkraut, kim chi, yogurt, kefir, and kombucha contain beneficial bacterial species that can help colonize the intestines and promote the growth of the good bacteria already present.

Eat foods high in prebiotics that help to feed your gut bacteria including garlic, onions, leeks, Jerusalem artichokes, dandelion greens, asparagus, bananas, legumes, oats, and avocados.

Don’t eat on the run or when you are under stress. Eating quickly or when you are stressed can decrease your ability to digest your food and can lead to overgrowth of potentially problematic gut bacteria.

Engage in stress reducing activities such as meditation, yoga, journaling, walking or exercise. High levels of stress hormones can decrease the population of beneficial gut bacteria.

If you take these steps to work on keeping the population of bacteria in the large intestine happy, it will go a long way in helping to promote regularity of bowel movements, decreasing risk of colon polyps and colon cancer, decreasing the development of pouches called diverticulosis (or when the become inflamed, diverticulitis), and decreasing the occurrence of the inflammatory bowel disease.

Taking supplements of probiotic bacteria can sometimes be helpful if the balance of bacteria have been thrown off, or if you are already experiencing the negative consequences of an altered intestinal ecosystem. In other cases, it may be helpful to have a stool test done to determine the makeup of the ecosystem of the gut and to determine what therapeutics may be the most helpful. New stool testing technology looking for DNA markers in the stool allows for identification of a greater number of organisms and is more sensitive for detecting potentially pathogenic organisms. This type of testing is available through naturopathic doctors and doctors practicing Functional Medicine.

Besides being the home for these beneficial bacteria, the primary roles of the large intestine include absorption of the nutrients produced by the bacteria and absorption of water from the stool. If the motility of the stool through the large intestine is too fast it can produce loose watery stools because less water is absorbed. If the stool sits in the large intestine for a long time, it can become very hard and dry due to too much water absorption. In addition to optimizing the colon bacteria, ensuring adequate fiber, water and magnesium intake and identifying and eliminating food sensitivities can help in promoting optimal motility.

This concludes our journey through the gastrointestinal tract. I hope that you now have a better understanding and appreciation for what happens after you put food into your mouth. There are many ways in which digestive function get off track. If any of the steps along the way are inefficient or incomplete, if you eat the wrong kinds of foods, if you eat too quickly, if you don’t chew your food, if you have too few good bacteria or too many bad bacteria or if the bacteria are in the wrong place, if your gut-immune system is overloaded or overactive, if you have low stomach acid or chronically take acid reducing medications, or countless other occurrences you will likely find yourself trying to manage and cope with digestive illness. On the other hand, if you take good care of your gut not only will you not likely have digestive illness, but your overall health will benefit as well.

Click here to read the first posts in Dr. Knight’s series.

About the Author

Dr. Peter Knight, ND

Dr. Knight, is a licensed doctor of naturopathic medicine specializing in nutritional and holistic treatment approaches to chronic health conditions. He is a graduate of Bastyr University and is in private practice at Healthy Living Health Care in Falmouth, Maine.

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