Fabaceae and Leguminosae, also known as legumes and beans, are great sources of fiber that have been around for 20,000 years in various cultures. In addition to being rich in fiber they contain B-vitamins, antioxidants, iron, folate, calcium, potassium, zinc and are a great source of plant-based protein. Legume is an umbrella term that includes all beans and pulses (edible seeds of legumes). Legumes have many health benefits such as reducing blood cholesterol, regulating blood sugar, lowering inflammation, and increasing beneficial strains of gut bacteria. These remarkable foods are easy to find, are cost effective, and can be prepared in a variety of delicious ways.
In this article we are going to focus on gut bacteria and how beans and legumes are a great source of soluble fiber, how they can positively affect our gut health and their benefits for our overall well-being. The human gastrointestinal (GI) tract is home to over 100 trillion microorganisms which together make up what is called the gut microbiota. Let’s explore how beans can improve our gut microbiota.
Fiber: Soluble vs. Insoluble
Fiber is a type of carbohydrate that the human body cannot digest. There are two types of fiber: soluble and insoluble.
Soluble fiber dissolves in water and turns into a gel form compound as it passes through our GI tract. Insoluble fiber does not dissolve in water, passing through the digestive system and bulking up the stool. Although we cannot digest certain fibers, our gut bacteria can feast on fiber and can break them down. This process is known as fermentation. The waste products of this process are often referred to as “postbiotics,” for example short chain fatty acid (SCFA). SCFA’s have been shown to be beneficial in regulating our neurologic systems (1).
Fiber is arguably the most important and studied nutritional component that can influence gut bacteria and improve gut-derived inflammation. Legumes contain many anti-inflammatory components such as dietary fiber, antioxidants, vitamins, and trace minerals. The relationship between legume consumption and gut bacteria and inflammation has become increasingly evident (2). The anti-inflammatory effect of fiber can lead to a lower incidence of metabolic, cardiac, neurodegenerative disorders. The soluble fibers in legumes and beans (e.g., inulin, beta-glucan, and galacto-oligosaccarides) lead to increased plasma and stool SCFA levels and subsequent improvement in diabetes, cholesterol levels, and metabolism (3,4).
The anti-inflammatory properties of legumes and their positive effect on our gut health should motivate you to increase your intake of them!
Gut bacteria play a vital role in various inflammatory disorders by interacting with our metabolic, endocrine, and immune system functions. Our endocrine system is also responsible for producing neurotransmitters (i.e., serotonin) that have potential to affect our mood. How fascinating!
The food we eat effects the structure and function of our gut bacteria. Diets high in fat and animal protein (“Western Diets”) tend to be lower in fiber, whereas in other parts of the world fiber intake is higher. This can lead to differences in gut bacteria profiles and adds an entirely new dimension to nutrition! Soluble fibers provide the basis for a varied gut bacterium and it is this increased diversity of the intestinal microbiome that promotes gut health, leading to improvements in physical and mental health (2,9).
When gut bacteria feast on fiber (prebiotics) the waste product of this fermentation process is called postbiotics. These waste products include important nutrients such as vitamins B and K, amino acids, and substances such as antimicrobial peptides that help to slow down the growth of harmful bacteria. Other postbiotics such as SCFAs also help healthy bacteria flourish (5).
Gut Health and Mental Health
Our gut microbiome also has an important role in our mental health and wellbeing. Our central nervous system and gut microbiome communicate (the gut-brain axis), and when our gut environment signals a pro-inflammatory state, this can have deleterious effects on psychiatric conditions such as anxiety and depression. Maintaining good gut health can play a role in treating and preventing these mental health disorders (6). Major depression (which is the most common mood disorder) has been linked to the levels of fecal SCFA concentration. Considering the anti-inflammatory property of SCFAs, dysbiosis followed by decreased levels of these gut microbes play a role in the inflammation process that may be related to the development of depression (7). Since legumes help regulate our gut health, they can make you feel better inside and out!
Mediterranean-Style eating patterns tend to have higher legume consumption. Adherence to the Mediterranean Diet has been shown to increase levels of SCFAs (8), which as we have mentioned play an important role in maintaining gut health. The consumption of legumes at least three times per week as part of the Mediterranean Diet was shown in a study to reduce inflammatory risk by 33% (3).
Diets high in animal protein (as opposed to plant protein which legumes provide) have been linked to unfavorable changes in gut microbiome composition and activity. High animal-protein diets, where the consumption of fruits and vegetables is lower, have been associated with pro-inflammatory and pathogenic conditions with a likely mechanism of action involving decreased SCFA production (9).
This pro-inflammatory profile can have a negative effect on specific medical conditions such as inflammatory bowel disease (IBD) and the development of colorectal cancer. Lower levels of gut inflammation can improve outcomes in IBD and prevent development of colorectal cancer, as suggested by the lower incidence and prevalence of colorectal cancer in Mediterranean countries (3).
Remember to include a variety of legumes and beans in your diet! Your gut bacteria will thank you, and you’ll feel so much better about your gut health.
1) Silva, Y., Frozza, R., & Bernardi, A. (2020, January 31). The role of short-chain fatty acids from gut Fmicrobiota in gut-brain communication. Frontiers in endocrinology. Retrieved May 9, 2022, from https://pubmed.ncbi.nlm.nih.gov/32082260/
2) Aranda-Olmedo, I., & Rubio, L. A. (2019, December 19). Dietary legumes, intestinal microbiota, inflammation and colorectal cancer. Journal of Functional Foods. Retrieved May 9, 2022, from https://www.sciencedirect.com/science/article/pii/S1756464619306310
3) Myhrstad, M. C. W., Tunsjo, H., Charnock, C., & The-Hansen, V. (n.d.). Dietary fiber, gut microbiota, and Metabolic Regulation-current status in human randomized trials. Nutrients. Retrieved May 9, 2022, from https://pubmed.ncbi.nlm.nih.gov/32210176/
4) Holscher, H. D. (2017, March 4). Dietary fiber and prebiotics and the gastrointestinal microbiota. Gut microbes. Retrieved May 1, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390821/
5) Wegh, C. A., Geerlings, S. Y., Knol, J., Roeselers, G., & Belzer, C. (2019, October 20). Postbiotics and their potential applications in early life nutrition and beyond. International journal of molecular sciences. Retrieved May 9, 2022, from https://pubmed.ncbi.nlm.nih.gov/31547172/
6) Clapp, M., Aurora, N., Herrera, L., Bhatia, M., Wilen, E., & Wakefield, S. (2017, September 15). Gut Microbiota’s effect on Mental Health: The gut-brain axis. Clinics and practice. Retrieved May 9, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5641835/
7) Skonieczna-Żydecka, K., Grochans, E., Maciejewska, D., Szkup, M., Schneider- Matyka, D., Jurczak, A., Loniewski, I., Kaczmarczyk, M., Marlicz, W., Czerwinska-Rogowska, M., Pelka-Wysiecka, J., Dec, K., & Stachowska, E. (2018, December 10). Faecal short chain fatty acids profile is changed in polish depressive women. Nutrients. Retrieved May 9, 2022, from https://pubmed.ncbi.nlm.nih.gov/30544489/
8) Dalile, B., Van Oudenhove, L., Vervliet, B., & Verbeke, K. (2019, August 16). The role of short-chain fatty acids in microbiota-gut-brain communication. Nature reviews. Gastroenterology & hepatology. Retrieved May 9, 2022, from https://pubmed.ncbi.nlm.nih.gov/31123355/
9) De Flippo, C., Cavalieri, D., Di Paola, M., Ramazzotti, M., Baptiste Poullet, J., Massart, S., Collini, S., Pieraccini, G., & Lionetti, P. (2010, August 2). Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa. Retrieved May 9, 2022, from https://www.pnas.org/doi/10.1073/pnas.1005963107.