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Written by: Sarah Glinski, Dt.P.

Your gut microbiota is made up of trillions of microbes, including bacteria, archaea, fungi, and viruses. Bacteria in the gut start to develop from the time you’re born. A healthy adult human typically harbours more than 1000 species of bacteria.1 Research into the human gut microbiota has exploded in recent years because it’s thought that these microbes have the potential to significantly impact both health and disease processes.1

By adulthood, your gut microbiota is fairly stable in terms of diversity and number of microbes. Usually, gut bacteria and their human host (i.e., the gut) live in a commensal manner. These commensal bacteria contribute to the immune defense system in the gut by resisting colonization of harmful bacteria and through the production of important metabolites that improve immunity against pathogens, maintain the integrity of the blood-brain barrier, and regulate important functions of the intestine. An imbalance of the gut microbiota is associated with several gastrointestinal conditions, including reflux, peptic ulcers, irritable bowel syndrome, and inflammatory bowel disease.2 For that reason, taking care of our gut microbiota is an important aspect of gut health.

 

How does diet impact good gut microbiota?

Several studies show that long-term dietary patterns can influence both the diversity and function of the gut microbiota and document the connection between the gut microbiota and people following a plant-based diet.2 There are also several compounds found in plant foods that positively contribute to overall gut health. While many people define a plant-based diet as a vegan diet (no animal products consumed), a plant-based diet can also include some animal foods. Rather than being a diet of exclusion, a plant-based diet focuses on how plant foods can be added to the diet to provide health benefits.



Dietary fibre and Polyphenols

Plant-based diets are high in dietary fibre because they include high-fibre foods such as fruits, vegetables, legumes, nuts, seeds, and whole grains. One of the key mechanisms by which a plant-based diet impacts the gut microbiota is through the influence that fibre has on the type, number, and consistency of bacterial species in the gut. Specifically, dietary fibre consumption is associated with an increase in beneficial bacteria like Bifidobacterium and Lactobacillus species. Both species are associated with protection of the gut wall by preventing the growth of pathogenic bacteria.3

In addition, fermentable dietary fibre has also been shown to act as a substrate for gut bacteria metabolism. Through the process of fermentation, metabolites are produced. One type of beneficial metabolites are short chain fatty acids (SCFAs). The SCFA butyrate plays a key role in immune system regulation and maintenance of gut barrier function. It also acts as an energy source for the epithelial cells of the gut, and it’s thought that SCFAs have anti-inflammatory effects in the intestine.2,3

Polyphenols are naturally occurring metabolites found in plant foods such as fruits, seeds, vegetables, tea, and cocoa products.2 Research on the antioxidant and anti-inflammatory effects of polyphenols have been shown to increase the number of beneficial bacteria in your gut, again the Bifidobacterium and Lactobacillus species, while reducing the growth of potentially harmful bacteria.3 In addition to promoting gut health, studies suggested that polyphenols may lower the risk of type 2 diabetes and heart disease, likely due to their anti-inflammatory and blood sugar-lowering effects. However, these are preliminary studies that have mostly been completed in animals, and more research is needed to see whether polyphenols are truly able to reduce the risk of these diseases in humans.4,5


 

How can I help my clients take care of their gut health?

In my clinical practice, I help my clients understand how important the gut microbiota is for gut health and how to take care of it. Nutrition is one of the easiest ways to promote a healthy gut microbiota, with fibre being our gut microbiota’s favourite fuel source. Adults need between 25 (for women) and 38 (for men) grams of fibre daily, but most Canadians are only getting half that amount.6 Following a plant-based diet rich in whole grains, pulses, fruits, vegetables, nuts, and seeds can be an excellent way to help your clients boost fibre intake and provide fuel for their gut microbes.

Polyphenols also act as a fuel source for our gut microbiota. To boost polyphenol intake, suggest clients try including the following plant foods in their diet :

  • Almonds
  • Apples
  • Apricots
  • Black or green tea
  • Black and red currants

 

  • Black beans
  • Blackberries
  • Broccoli
  • Carrots
  • Cherries
  • Dark chocolate

  • Hazelnuts
  • Pecans
  • Spices like cumin, curry powder, cinnamon, and clove
  • Spinach

 

 

Often, foods with bright colours - like red, dark green and purple - tend to be higher in polyphenols. Eat the rainbow to boost your polyphenol intake!7

I hope that this has been a helpful summary of the ways to maintain gut health and how dietary fibre found in plant-based diets contribute to the good bacteria in our guts that help to keep us healthy.

Looking for more? Check out our Gut Health Kick Start Guide  for more tips you can share with your clients on how to take care of their gut microbiota.


Sarah Glinski is a Registered Dietitian and has experience in chronic disease management, digestive disorders, and oncology. She holds a Bachelor of Science in Biology and a Bachelor of Science in Food and Nutrition Sciences. Sarah is currently a member of the 2021 Becel Centre for Heart Health Steering Committee, a team of registered dietitians working to create practical and relevant content, for which she has been compensated by Becel Center for Heart Health.

References

  1. Shreiner, A. B., Kao, J. Y., Young, V. B. 2015. The gut microbiome in health and disease. Curr Opin Gastroenterol. 31(1): 69-75. Sourced June 9, 2021.
  2. Tomova, A., Bukovsky, I., Rembert, E., Yonas, W., Alwarith, J., Barnard, N. D., Kahelova, H. 2019. The Effects of Vegetarian and Vegan Diets on Gut Microbiota. Front Nutr. 2019 (6): 47 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6478664/ Sourced June 7, 2021.
  3. Sakkas, H., et al. 2020. Nutritional Status and the Influence of the Vegan Diet on the Gut Microbiota and Human Health. Medicina (Kaunas). 56(2): 88 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7073751/ Sourced June 7, 2021.
  4. Kim, Y., Keogh, J. B., Clifton, P. M. 2016. Polyphenols and Glycemic Control. Nutrients. 8(1): 17 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728631/ Sourced June 9, 2021.
  5. Tangney, C., Rasmussen, H. E. 2014. Polyphenols, Inflammation, and Cardiovascular Disease. Curr Atheroscler Rep. 15(5): 324 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3651847/ Sourced June 9, 2021.
  6. Recommended Daily Fibre Intake. Canadian Digestive Health Foundation. https://cdhf.ca/health-lifestyle/recommended-daily-fibre-intake/ Sourced June 9, 2021.
  7. Pérez-Jiménez, J., Neveu, V., Fos, F., Scalbert, A. 2010. Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database. European Journal of Clinical Nutrition. 64(2010): S112-S120. Sourced June 9, 2021.