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The Science Nook on Plant-Based Eating and Gut Microbiota

by Jenna Koroly, MS, RD, CSOWM, CDN

Both gut microbiota and plant-based eating are continuing to be studied, as well as talked about by health professionals and patients. The below review explores how vegetarian/vegan and omnivore eating patterns influence gut microbiota. The microbiota is “the total of all microbial taxa associated with human beings (bacteria, viruses, fungi, protozoa, archaea),” while the microbiome is “the catalog of these microbes and their genes.” Remarkably, although humans are roughly 99.9% identical to one another when considering their genomes, they can be 80-90% different from one another when considering their gut microbiomes [i].



The Effects of Vegetarian and Vegan Diets on Gut Microbiota

Journal: Frontiers in Nutrition

In this article, the authors provide an in depth review of the current research on vegetarian/vegan versus omnivore eating patterns and gut microbiota. They report on how these different eating patterns influence the diversity and richness of microbiota, specific bacteria, and plant food components. Below are a number of highlights from their myriad of findings.


1. Plant-based eating patterns promote a greater diversity in microbiota, which is associated with positive effects on BMI, obesity, and arterial compliance. There is an association between “local microbial richness” and long-term intake of fruits and vegetables [Klimenko et al., 2018 as cited in Tomova et al., 2019]

2. The addition of whole-grain barley, brown rice, or a mixture of both to one’s eating pattern leads to an increase in microbial diversity [Martinez et al., 2013 as cited in Tomova et al., 2019]

3. Participants with obesity show a decrease in the Bacteriodetes:Firmicutes ratio, primarily present in healthy adults’ intestinal microbiome, and an increase in Proteobacteria, which is a pro-inflammatory phylum [Verdam et al., 2013 as cited in Tomova et al., 2019]

4. Western eating patterns include more ultra-processed foods and nutrients not containing cells. Because these are more easily absorbed in the small intestine, the colon does not receive nutrients, which may alter composition and metabolism of gut microbiota. On the other hand, whole plant foods demonstrate protective effects and promote growth of beneficial bacteria in the colon [Zinocker & Lindseth, 2018 as cited in Tomova et al., 2019]

5. A high-protein eating pattern by nature tends to decrease carbohydrate intake, which in turn may result in a decrease in butyrate-producing bacteria and thus a proinflammatory state and increased risk of colorectal cancer [Sheflin et al., 2016 as cited in Tomova et al., 2019]

6. Polyphenols in plant foods increase Bifidobacterium and Lactobacillus, which offer anti-pathogenic effects, anti-inflammatory effects, as well as cardiovascular protection [Singh et al., 2017 as cited in Tomova et al., 2019]. Plant polyphenols also hold anti-cancer, anti-inflammatory, and antioxidant effects [Panche et al., 2016; Ono et al., 2012; Hossen et al., 2017 as cited in Tomova et al., 2019]

7. Microbiota convert bile acids from cholesterol to secondary bile acids, which are found in tissue and feces. These secondary bile acids are associated with inflammatory bowel disease, liver cancer, and colon cancer [Donia & Fischbach, 2015; Gerard, 2013 as cited in Tomova et al., 2019]

For the Patient and Caregiver

When thinking of the health of your gut microbiota, consider moving towards a plant-based eating pattern to diversify the ecosystem in your gut. Aim for a variety of vegetables, fruits, whole grains, and plant polyphenols such as seeds, tea, and cocoa products.

For the Healthcare Team

The old saying “you are what you eat” comes to fruition when referencing gut microbiota. Consider educating your patients about the microbiome, and encouraging plant-based eating high in fiber and low in saturated fat from animal products, which leads to increased cholesterol. Depending on the patient, highlighting the specific health benefits that a healthy microbiota holds, including decreased risk of chronic disease, may prove beneficial.


[i] Tomova A, Bukovsky I, Rembert E, Yonas W, Alwarith J, Barnard ND, Kahleova H. (2019). The effects of vegetarian and vegan diets on gut microbiota. Front. Nutr. 6:47. doi: 10.3389/fnut.2019.00047

  1. Jenna – thanks so much for this useful information. There is more and more evidence everyday of the benefits of a plant-based diet for most of us. MK

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