Maybe you’ve noticed by now that I’ve got a major passion for gut health. It really is one of those central areas of your body that, possibly more than any other system, can make or break your health. Today I want to delve into the gut microbiome, or the ecosystem of bacteria living in your digestive tract and how they influence your health. In my next article, I’ll dig deep into what factors influence whether that ecosystem is health promoting or health undermining.
This collection of bacteria is similar to a forest ecosystem, but in this case, population changes happen more rapidly since the life cycles of the bacteria are measured on a much shorter time scale than those of trees, plants and animals. The composition of species changes dramatically, even from day to day, based on conditions.
The digestive tract is home to the vast majority of your microbiome. An estimated 4 to 5 pounds of bacteria live here, with the majority of your gut microbes residing in your large intestine or colon (The last few feet of your digestive tract), and a comparatively much smaller number living further up in the small intestine and stomach.
There is a large and ever-expanding body of research confirming that the complement of bacteria making their home in your colon has EVERYTHING to do with your health. It affects digestive health (obviously), but dramatically influences other aspect of your health as well. Dysbiosis is the term used for imbalances in the gut ecosystem, whether from the wrong types of bacteria, overgrowth of yeasts or the presence of harmful viruses or parasites.
Here are six aspects of your health that are influenced by your microbiome:
Certain bacteria are responsible for stimulating your own gut cells to produce proper levels of serotonin. In mouse experiments, if these bacteria were absent, serotonin levels fell by 60%! And the research showed that this is likely true for humans as well. (1) Disruption of this process is one of the ways that dysbiosis plays a role in depression. Another way is that dysbiosis contributes to leaky gut, which leads to body-wide inflammation including brain inflammation. Brain inflammation is a major cause of depression and has little to do with neurotransmitter deficiency. Depression with this root cause is therefore less likely to be benefitted by antidepressant medications, which are designed to increase levels of neurotransmitters like serotonin.
Certain types of bacteria manufacture vitamin K and several B vitamins on site in the colon, reducing the need to get these vitamins from foods.(2, 3, 4) Some types of bacteria ferment cellulose, the fiber found in many plant foods that does not get broken down by your digestive processes in the stomach and small intestine. This fermentation process produces short chain fatty acids, which nourish the cells lining the large intestine, decrease your risk of colon cancer (5), and also provide about 6-9% of your daily calories. (6)
Certain less helpful forms of bacteria actually act as a chronic infection in your colon, contributing to intestinal inflammation and leaky gut, which increases body-wide inflammation. This can lead to heart disease, asthma, allergies, eczema and autoimmune diseases like rheumatoid arthritis, multiple sclerosis, Hashimoto’s thyroiditis and more. (7, 8, 9, 10)
4. Cholesterol levels
Depending on your gut bugs’ behavior, more or less cholesterol will be eliminated via the stool or recycled back into circulation.
5. Hormone balance
The liver processes all excess hormones, whether from your own endocrine system, birth control pills, hormone replacement therapy or xenoestrogens (chemical compounds that act like estrogen in the body). The hormones are attached to carrier proteins to keep them water soluble and dumped into the bile for elimination via the stool. However if you have dysbiosis, the “bad bugs” produce excess enzymes that clip the bond between the estrogen and the protein carrier, thus allowing the estrogen to be reabsorbed. Elevated estrogens in the body contribute to menstrual cramps, acne, endometriosis and hormone related cancers.
6. Immune system function
Certain bacteria help to educate and stimulate your immune system so that it functions optimally. (11, 12) Without proper immune system education, conditions such as allergies, asthma and eczema crop up, and autoimmune diseases become more likely.
Keeping your internal ecosystem healthy is not as simple as taking a probiotic pill each day. One of the main reasons that healthy habits like staying hydrated, eating a varied, vegetable-rich diet (13), exercising (14–16), getting plenty of quality sleep (17) and handling stress well (18) are important is that they promote an internal environment that fertilizes the helpful bacteria and discourages growth of the unhelpful ones. All of these things benefit our human cells directly, but they also benefit us indirectly by nourishing and supporting healthy diversity in our microbiomes.
I have a lot more information to share with you regarding the specifics of supporting a healthy internal ecosystem. Please stay tuned next month for my next article:
How to tend your garden: Tips to cultivate the right gut bacteria and keep them thriving
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Wishing you vibrant health,
1. Yano JM, Yu K, Donaldson GP, et al. Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis. Cell. 2015;161(2):264-276. doi:10.1016/j.cell.2015.02.047.
2. Conly JM, Stein K, Worobetz L, Rutledge-Harding S. The contribution of vitamin K2 (metaquinones) produced by the intestinal microflora to human nutritional requirements for vitamin K. Am J Gastroenterol. 1994;89(6):915-923.
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8. Fasano A. Zonulin, regulation of tight junctions, and autoimmune diseases. Ann N Y Acad Sci. 2012;1258(1):25-33. doi:10.1111/j.1749-6632.2012.06538.x.
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11. Hill DA, Artis D. Intestinal Bacteria and the Regulation of Immune Cell Homeostasis. Annu Rev Immunol. 2010;28(1):623-667. doi:10.1146/annurev-immunol-030409-101330.
12. Purchiaroni F, Tortora A, Gabrielli M, et al. The role of intestinal microbiota and the immune system. http://www.europeanreview.org/wp/wp-content/uploads/323-333.pdf. Accessed April 5, 2017.
13. Heiman ML, Greenway FL. A healthy gastrointestinal microbiome is dependent on dietary diversity. 2016. doi:10.1016/j.molmet.2016.02.005.
14. Clarke SF, Murphy EF, O’Sullivan O, et al. Exercise and associated dietary extremes impact on gut microbial diversity. Gut. 2014;63(12):1913-1920. doi:10.1136/gutjnl-2013-306541.
15. Campbell 1☯ SC, Wisniewski PJ, Noji M, et al. The Effect of Diet and Exercise on Intestinal Integrity and Microbial Diversity in Mice. doi:10.1371/journal.pone.0150502.
16. Mika A, Fleshner M. Early-life exercise may promote lasting brain and metabolic health through gut bacterial metabolites. Immunol Cell Biol. 2016;94(2):151-157. doi:10.1038/icb.2015.113.
17. Benedict C, Vogel H, Jonas W, et al. Gut microbiota and glucometabolic alterations in response to recurrent partial sleep deprivation in normal-weight young individuals. Mol Metab. 2016;5:1175-1186. doi:10.1016/j.molmet.2016.10.003.
18. Carabotti M, Scirocco A, Maselli MA, Severi C. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Ann Gastroenterol. 2015;28:203-209. www.annalsgastro.gr. Accessed April 5, 2017.