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The Marvelous Microbiome

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By Mary Purdy, MS, RDN

(Some portions of the below article are taken from Mary Purdy’s book “The Microbiome Diet Reset” )

Who knew that collectively, a group of teeny tiny life forms in our intestines could have such an impact on our health? Our gut microbiome, made up of trillions of microorganisms such as bacteria, fungi and viruses, (and their genes) not only plays a role in the digestion and absorption of our nutrients, it actually helps to ensure the integrity of our gut lining, protects against pathogens, supports our immune function, aids in detoxification and synthesizes a variety of vitamins. It also helps to determine how much energy we burn, how much fat we store, and more research is emerging on the significant effect it has on brain function and mood. Additionally, we are beginning to understand and connect the dots between dysbiosis (an imbalance of microbial populations in the gut) and common chronic conditions like inflammatory bowel disease, diabetes, obesity, cardiovascular disease, and Alzheimer’s disease.

Particularly of concern these days is the interesting connection between microbial diversity and a host of autoimmune diseases. One of the ways the gut plays a role here is via maintaining a strong and resilient “intestinal barrier” or “gut wall” which keeps unfriendly microbes and other large molecules from escaping the digestive tract and making their way into the bloodstream. The integrity of this wall relies on the ability of a healthy microbial community nourished by a fiber-rich diet to create “short chain fatty acids” which nourish the cells of the intestine and strengthen the gut barrier. As dietitians know, from countless dietary recalls, most Americans are significantly lacking fiber in their diets. If that intestinal barrier breaks down as a result of bacterial starvation, imbalances or ongoing exposure to toxic compounds, foreign bodies are more able to cross from the inside of the intestines to the bloodstream and potentially cause an overactive immune response. (Proal 2013) Additionally, these short chain fatty acids have other significant effects on other bodily processes including supporting healthy cholesterol levels, helping us to feel full, potentially increasing calorie burning and promoting microbial diversity which…keeps the healthy cycle going. (Singh, 2017,Hills 2019)

If you haven’t already guessed, what plays a significant role in shaping this internal ecosystem? Diet! For your patients who may be struggling with some of the aforementioned conditions, working with them to support a healthy and resilient microbiome may be a key piece to help them address some of these imbalances. Below are 5 important dietary microbiome supporters and 5 disruptors for you to consider as part of your assessment and recommendations for a healthier and more resilient microbiome.

5 Supporters for optimal Microbial Health

  1. Surprise! Fiber. Ensuring sufficient amounts of this key nutrient found in beans, grains, nuts, seeds, fruits and vegetables is one of the best ways to keep those gut bugs well fed and able to carry out their numerous functions. Remember it’s about variety so while carrots and chickpeas are fantastic, the idea is to get at least 30 different plant foods weekly to ensure microbial diversity.
  2. Phytochemicals. These are those beneficial and colorful compounds found in plants, like polyphenols, which have been shown to inhibit the growth of pathogenic bacteria, stimulate beneficial bacteria, and also reduce inflammation in the gut, a hallmark of numerous diseases. (Ozdal. 2016) Produce grown in healthy soil that should be teeming with its own microbes is going to provide additional exposure to friendly microorganisms. Once again, diversity is key here. Encourage a plate that’s as polychromatic as possible.
  3. Probiotic rich foods. This includes both cultured foods like yogurt and kefir but also unpasteurized fermented foods like sauerkraut, kimchi, kvass and a variety of the veggies from beet and carrots to radishes that are finding themselves in the jars of the popular new fermented foods craze. These helpful foods not only provide the host with beneficial microorganisms, but they help to reduce the presence of less favorable gut bacteria. Additionally, fermentation also has been shown to increase the antioxidant activity and availability of the nutrient content of many foods. (Chun 2004)
  4. Pre-biotics. These are the undigestible components of foods that are essentially feeding our probiotics and helping them to thrive. Obviously, there is some crossover with the fiber category, but I wanted to highlight some specific types of fiber called “inulin” and fructo- oligosaccharides” or “FOS” found in foods like onions, garlic, maple syrup and bananas. Studies have shown that regular inclusion of this food group has helped to improve cardiovascular and joint inflammation issues (Hill 2019)
  5. Beta Glucans: Some emerging research has also shown that compounds in mushrooms and grains like oats or barley called “beta glucans” have both immune building and prebiotic properties that enhance the growth of some of our bacterial buddies as well as protect the gut lining. (Richter, 2015; Vetvicka, 2019) Pretty easy to get patients to enjoy a bowl of oatmeal or toss some mushrooms in their salad, soup or stir fry periodically. Added benefit: Consumption of beta-glucans have also been linked to lower cholesterol levels. Is food medicine or what?

5 detractors for optimal microbial health

  1. Refined sugar and carbohydrates. Higher consumption of this type of carbohydrate is associated with lower gut microbe diversity and are also the foods upon which the “bad” bacteria thrive. High fructose corn syrup in particular has been shown to alter those helpful short chain fatty acids (SCFA’s), damage the intestinal wall and drive inflammation. (Li, 2019) Steer your patients towards fiber rich versions of foods they may love and help curb sweet cravings with new flavors often found in herbs and spices which offer an additional anti- inflammatory and digestive boost to boot!
  2. High amounts of red and processed meats have also been shown to alter the gut microbiome in a less favorable direction by helping the bad guys flourish and leading to intestinal inflammation. (David, 2014; Hill, 2019) They have been associated with lower levels of short chain fatty acids (SCFA’s) and with higher levels of a unhealthy compound, called “Trimethylamine N-oxide” or the more palatable “TMAO” found in the bloodstream that can increase the risk for heart disease. (Singh, 2017)
  3. Pesticides. Numerous animal and observational studies indicate that these chemicals significantly alter the gut microbiome. (Mendler, 2020, Narrowe 2015) If a chemical was designed to destroy pests, we can imagine that it will likely have some impact on the bugs residing in our intestines, especially with chronic long-term exposure. If organic or pesticide free produce is not available to those with whom you work, suggest peeling or thoroughly washing to reduce the residues as much as possible.
  4. Non-Nutritive Sweeteners. Also known as “artificial sweeteners” these sugar replacements have been shown to alter the composition and function of the microbiota. Ironically, like sugar, consuming these sweeteners may also result in dysbiosis. (Ruiz-Ojeda , 2019) Encourage patients to add a touch of honey or maple syrup instead.
  5. Stress. Ok, so this isn’t food, but it’s so key, not mentioning it would be a disservice. I can’t call myself a true “integrative dietitian” if I don’t bring at least one lifestyle component into this conversation. The production of the hormone, cortisol, under chronically stressful circumstances (know anyone with those?) can negatively affect the makeup of the microbiome and reduce the production of short chain fatty acids. Interestingly enough, a disruption of microbiome status has been associated with stress related disorders. (Maltz, 2019, Foster, 2017)

As dietitians, we are already a part of ensuring a healthy diet to promote optimal health. Hopefully these tips can help us go the extra mile with our patients to help address and resolve underlying imbalances, while at the same time promoting foods that also serve our equally important eco-system, our environment.

References:
1. Chun, O. K., Smith, N., Sakagawa, A., & Lee, C. Y. (2004). Antioxidant properties of raw and processed cabbages. International journal of food sciences and nutrition, 55(3), 191-199.
2. David, L., Maurice, C., Carmody, R. et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature 505, 559–563 (2014).
3. Foster, J., Rinaman,l., Cryan,J. Stress & the gut-brain axis: Regulation by the microbiome. Neurobiology of Stress Volume 7, December 2017, Pages 124-136
4. Hills RD Jr, Pontefract BA, Mishcon HR, Black CA, Sutton SC, Theberge CR. Gut Microbiome: Profound Implications for Diet and Disease. Nutrients. 2019;11(7):1613. Published 2019 Jul 16. doi:10.3390/nu11071613
5. Li, J., Yu, R., Zhang, L. et al. Dietary fructose-induced gut dysbiosis promotes mouse hippocampal neuroinflammation: a benefit of short-chain fatty acids. Microbiome 7, 98 (2019).
6. Maltz RM, Keirsey J, Kim SC, et al. Social Stress Affects Colonic Inflammation, the Gut Microbiome, and Short-chain Fatty Acid Levels and Receptors. J Pediatr Gastroenterol Nutr. 2019;68(4):533-540.
7. Mendler A, Geier F, Haange SB, et al. Mucosal-associated invariant T-Cell (MAIT) activation is altered by chlorpyrifos- and glyphosate-treated commensal gut bacteria. J Immunotoxicol. 2020;17(1):10-20.
8. Narrowe AB, Albuthi-Lantz M, Smith EP, et al. Perturbation and restoration of the fathead minnow gut microbiome after low-level triclosan exposure. Microbiome. 2015;3:6. Published 2015 Mar 3. doi:10.1186/s40168-015-0069-6
9. Ozdal T, Sela DA, Xiao J, Boyacioglu D, Chen F, Capanoglu E. The Reciprocal Interactions between Polyphenols and Gut Microbiota and Effects on Bioaccessibility. Nutrients. 2016;8(2):78. Published 2016 Feb 6. doi:10.3390/nu8020078
10. Proal AD, Albert PJ, Marshall TG. The human microbiome and autoimmunity. Curr Opin Rheumatol. 2013 Mar;25(2):234-40.
11. Richter J, Svozil V, Král V, Rajnohová Dobiášová L, Vetvicka V. β-glucan affects mucosal immunity in children with chronic respiratory problems under physical stress: clinical trials. Ann Transl Med. 2015;3(4):52. doi:10.3978/j.issn.2305-5839.2015.03.20
12. Ruiz-Ojeda, F, Plaza-Díaz, J, Gil, A. Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials. Adv Nutr. 2019 Jan; 10(Suppl 1): S31–S48
13. Schroeder BO. Fight them or feed them: how the intestinal mucus layer manages the gut microbiota. Gastroenterol Rep (Oxf). 2019;7(1):3–12. doi:10.1093/gastro/goy052
14. Singh, R.K., Chang, H., Yan, D. et al. Influence of diet on the gut microbiome and implications for human health. J Transl Med 15, 73 (2017)
15. Vetvicka V, Vannucci L, Sima P, Richter J. Beta Glucan: Supplement or Drug? From Laboratory to Clinical Trials. Molecules. 2019;24(7):1251. Published 2019 Mar 30. doi:10.3390/molecules24071251

Mary Purdy, MS, RDN is an Integrative and Eco-Dietitian, with a Master’s Degree from Bastyr University where she is currently adjunct faculty. She has been in clinical practice for over 12 years in both private practice, as clinical supervisor at Bastyr’s Teaching Clinic and with the Wellness Company, Arivale, using a personalized medicine and functional nutrition approach. She has given over 100 nutrition workshops, speaks regularly at health and nutrition conferences and was the keynote speaker at Bastyr University’s Commencement Ceremony 2019. She serves on the boards of Hunger and Environmental Nutrition and Dietitians in Integrative and Functional Medicine which she chaired in 2018. Additionally, she hosts the podcast “The Nutrition Show”, authored the books “Serving the Broccoli Gods” and “The Microbiome Diet Reset”, and is a consultant for creating a sustainable and resilient food system that supports our environment and helps to mitigate climate change. Her website is www.marypurdy.co