Written by Gina Wren
Diet is the biggest environmental factor affecting the trillions of microorganisms living in our gut (your “microbiome”). Alterations to microbiome composition can occur very rapidly following a diet change. Two human study groups that changed to either a plant-based diet, rich in grains, fruits, and vegetables, or an animal-based diet, showed dramatic changes in microbiome composition in just five days (1).
It is widely accepted that higher microbiome diversity (lots of different species of bacteria), means a healthier gut. Microbiome diversity can be promoted by a diet rich in plants (2). Despite the copious amounts of information around the health benefits of plants. Your Mum telling you to eat up the leftover broccoli on your plate, only 29% of Brits eat their five a day (3). Most of us need to up the amount of plant-based foods in our diets. But what components of plant-based foods are good for our microbiome?
What most people don’t know is that fibre is a type of carbohydrate. It is found in all plants. Humans actually can’t digest dietary fibre; its primary purpose is to bulk out your stool and feed the gut microbiome (4). Bacteria that are deprived of fibre can start to eat away at the gut lining or other ‘leftover’s’ found in the gut. Including undigested protein, increasing the risk of infection (5).
Plant and animal proteins influence the microbiome composition differently. For example, consuming pea protein decreases the number of pathogenic bacteria. Whilst increasing the number of good bacteria in the gut, whereas animal proteins have the opposite association (6). These good bacteria help to reduce gut inflammation and increase the strength of the gut lining (7).
The gut microbiome is impacted by the amount and type of fats in the diet. A plant-based diet can be naturally lower in fat. And primarily made up of mono and polyunsaturated fats (e.g. the types you find in nuts, seeds, avocados, and olive oil). These favour good bacteria and help to reduce the risk of chronic disease (6).
Polyphenols are naturally occurring protective plant compounds. These are found in abundance in seeds, brightly coloured vegetables, green tea, dark chocolate, and red wine (you can thank me later!). They have anti-pathogenic and anti-inflammatory effects (all in moderation). Your beneficial bacteria love them and are protective for cardiovascular health (8).
We have seen that eating more plants helps to feed your good gut bacteria, plants and the gut microbiome are intrinsically linked. Interestingly, these good bacteria can ‘talk’ to other organs and may even reduce the risk of disease. A 16-week plant-based diet increased gut bacteria that are associated with improvements in body weight, body composition and blood sugar control (9). Although preliminary research, this is a promising development. It could help with the future prevention of obesity and Type-2 diabetes. Also, it is worth being aware that certain unhelpful bacteria may contribute to heart disease. They may be producing compounds that contribute to blocked arteries. People eating a more plant-based diet tend to have lower levels of the bacteria producing these compounds (10,11).
We aren’t saying cut out animal products but what we do know is that having a variety of plant-foods is the best way to maintain optimal health. There is clearly a link between eating more plants and the gut microbiome. In fact having 10 portions of fruit or veg per day, instead of the recommended five, can increase your lifespan by up to a third, and there is no upper limit to the benefit (12). Research also shows that variety, as well as quantity, is just as important, to keep our gut microbiome diverse, we need to aim for 30 different plant-based foods a week.
So the next time you think about passing on the veg, you might want to give a second thought to your gut bacteria who are waiting to be fed! Eat those plants and the gut microbiome will thank you!
About the author
Gina Wren is currently a postgraduate student at Imperial College London focusing on the microbiome in health & disease.
She graduated from Durham University in 2016 after studying Natural Sciences. Following this, Gina worked at Innovate UK for two years helping to drive innovation and business growth in the health & life sciences industry.
- David, L. A., Maurice, C. F., Carmody, R. N. et al. (2014). Diet rapidly and reproducibly alters the human gut microbiome. Nature, 505(7484) .
- Klimenko, N. S., Tyakht, A. V., Popenko, A. S., Vasiliev, A. S., Altukhov, I. A., Ischenko, D. S., … & Alexeev, D. G. (2018). Microbiome Responses to an Uncontrolled Short-Term Diet Intervention in the Frame of the Citizen Science Project. Nutrients, 10(5).
- NHS Digital (2017). Fruit and Vegetables. Retrieved from: http://healthsurvey.hscic.gov.uk/data-visualisation/data-visualisation/explore-the-trends/fruit-vegetables.aspx
- Tomova, A., Bukovsky, I., Rembert, E., Yonas, W., Alwarith, J., Barnard, N. D., & Kahleova, H. (2019). The Effects of Vegetarian and Vegan Diets on Gut Microbiota. Frontiers in nutrition, 6(47).
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- Cardona, F., Andrés-Lacueva, C., Tulipani, S., Tinahones, F. J., & Queipo-Ortuño, M. I. (2013). Benefits of polyphenols on gut microbiota and implications in human health. The Journal of nutritional biochemistry, 24(8).
- (2019). Short-term study suggests vegan diet can boost gut microbes related to body weight, body composition and blood sugar control. ScienceDaily. Retrieved from www.sciencedaily.com/releases/2019/09/190916185819.htm
- Janeiro, M. H., Ramírez, M. J., Milagro, F. I., Martínez, J. A., & Solas, M. (2018). Implication of Trimethylamine N-Oxide (TMAO) in Disease: Potential Biomarker or New Therapeutic Target. Nutrients, 10(10).
- Wang, Z., Bergeron, N., Levison, B. S., Li, X. S., Chiu, S., Jia, X., … & Krauss, R. M. (2018). Impact of chronic dietary red meat, white meat, or non-meat protein on trimethylamine N-oxide metabolism and renal excretion in healthy men and women. European heart journal, 40(7)
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