Eat More Legumes and Feed Your Microbiota

by Kirke on October 27, 2013

Legumes, some better known as beans, a term well known in expressions like being full of beans, closely related to being full of hot air (do I hear a song about musical fruit?); or where what you might know does not amount to a hill of beans; or that if you tell what you know you have spilled the beans. Well, I am going to spill the beans on what I know about beans, which amounts to at least as much as a good size hill of beans.

Legumes have been an important part of the life of humans for thousands of years, second in the human diet after the grasses (grains). A bean’s protein content average twice the amount found in grains, and they are an excellent source of iron and B vitamins. They contain more vitamins A and C when eaten green, but then they offer less protein. Beans can be dried and stored for later use as a concentrated source of protein and carbohydrate. Many beans are good sources of Vitamin K, the “blood coagulation” vitamin. Interestingly, there are parts of beans that we cannot digest, and these non-digestible fibers support beneficial bacteria in our colon that in turn synthesize more Vitamin K. This is just one example of how eating legumes feed our microbiota, the population of beneficial bacteria that call the human body home. Decidedly, legumes play intriguing roles in more relationships involving biology than found in the most convoluted soap operas.

Decidedly, legumes play intriguing roles in more relationships involving biology than found in the most convoluted soap operas.

Legumes and Relationships

In one episode of this biological soap opera legumes carry on a twofold, binary relationship with grains. For centuries the two have been successfully paired together in different culture’s diets. Asian cultures match soybeans with rice; Central Americans pair corn with common beans; in the Near East lentils or chickpeas are served with wheat products. These marriages bring a missing component of each food to the table. Legumes are low in a sulfur containing amino acid, which grains provide. Grains are low in the amino acid lysine, which legumes contribute to the mix. The second tale of a mutually beneficial relationship is found in the sphere of agriculture. Grains deplete the soil as they grow, whereas legumes actually enrich the soil, supplying essential nitrogen compounds. In Latin America you might see bean vines climbing right onto corn stalks. And farmers have rotated crops at least since Roman times, planting grains and legume crops in alternate years. Today this sound ecological process is the exception rather than the rule thanks largely to monoculture crops promoted by (bad) seed companies like Monsanto. This is a thinly veiled attempt to monopolize our nation’s agriculture, yielding profits by selling nitrogen fertilizers instead of harvesting sustainability.

Iacopi Farms Blanched Butter Beans from Half Moon Bay
Iacopi Farms Blanched Butter Beans from Half Moon Bay
Iacopi Farms Blanched Butter Beans from Half Moon Bay

 

The agricultural twofold relationship between legumes fixing the soil with nitrogen, along with their dietary complimentary match with grains, leads me to a third twofold relationship: that between ourselves and the bacterial microbiome that lives within our gastrointestinal (GI) tract. What is meant by legumes fixing nitrogen is that they facilitate the conversion of N2 in the atmosphere into NH3, a form of nitrogen that other living things can use. Legumes do this through a symbiotic interaction of colonies of bacteria that move from the soil to live in nodules on the plant’s roots. The plant provides energy needed by the bacteria through photosynthesis, and in return the bacteria provide NH3 the plants need. Once the legume crop is grown, the nitrogen is either harvested as food for animals or humans to consume, or it is plowed back into the soil for the benefit of future crops.

Our Microbiome and Immunity

While bacteria’s relationship with legumes in the sphere of agriculture is wondrous, their symbiotic alliance with us is an even more amazing story. From the moment of our birth, when beneficial bacteria are passed onto us by our mothers (and then by our relatives, pets, and environment), the microorganisms provide a protective barrier in our GI tract, protecting us from pathogenic bacteria. By our second birthday, we’ve each developed a personal population of distinctive micro-organisms AKA: our microbiome (referring to the bacteria’s DNA) fingerprint, unique to us throughout our life. Specific numbers of each of the more than 500 bacteria strains will ebb and flow, influenced by our diet, stress, age, health status, pathogens we encounter and the antibiotics we ingest to fight them. All this time, our body tries to maintain populations of the strains that make up our fingerprint.

Fava Beans, at Home in the Pod, and Blanched, courtesy of Iacopi Farms
Fava Beans, at Home in the Pod, and Blanched, courtesy of Iacopi Farms
Fava Beans, at Home in the Pod, and Blanched, courtesy of Iacopi Farms

 

From around the turn of the 21st century, scientists have been learning more and more about the importance of the microbiota. They’ve found that together these micro-organisms function like an additional organ in our immune system.

They’ve found that together these micro-organisms function like an additional organ in our immune system.

They are an essential part of our gut-associated lymphoid tissues (GALT), a prominent part of the mucosal-associated lymphoid tissue (MALT) comprising 70 percent of our entire immune system. These are the tissues that produce, store or process white blood cells, or lymphocytes. Pathogenic microorganisms that make it as far as the digestive system encounter these cells, which then work to identify and attack the interlopers. If a body supports a healthy microbiota, its immune system will be a robust one. Studies are now showing that bacteria in our gut actually communicate with the surface cells (epithelial) on our intestines leading to metabolic/immunologic reactions from the underlying lymphoid cells. The phenomenon is called bacterial-epithelial ‘crosstalk.’

Probiotics and Prebiotics

Probiotics are foods or supplements that contain live cultures of certain strains of bacteria. These are useful when our microbiota has been damaged by antibiotics, infections, or diseases including diarrhea, inflammatory bowel diseases, colon cancer, infected pancreatic necrosis, and postoperative liver transplant infections. They can be found as active live cultures in some yogurts, kefir (cultured milk), Yakult (a cultured dairy product of Japanese origin), as well as fermented foods like sauerkraut, and natural pickles. Probiotics are also available in supplement form. Ask your doctor if taking probiotics is right for you, and if so, what brands he recommends. Legumes are an example of a prebiotic.

Legumes are an example of a prebiotic.

As defined by the 2010 Dietary Guidelines for Americans, “prebiotics are a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health.” Prebiotics are being packaged for market as a supplement, and some are worthwhile, but they are already found in many of the foods we eat. They are food components not digested (or partially digested) by human digestive enzymes, but they can still benefit us by acting as a substrate (a medium for growth) supporting the proliferation of beneficial bacteria in the colon, thereby improving our health and well being. The bacteria consume the unused fiber by fermentation. By consuming certain types of fermentable fiber like oligosaccharides, beta-glucan, gums, resistant starch, and pectin, beneficial microbial populations will thrive, particularly, bifidobacteria and lactobacilli.

In Pod and Shucked Cranberry Beans from Iacopi Farms
In Pod and Shucked Cranberry Beans from Iacopi Farms
In Pod and Shucked Cranberry Beans from Iacopi Farms

 

What is Generally Thought…

Epidemiological studies have yet to be done concerning the human microbiota system. Random controlled trials, the gold standard for establishing cause and effect, are few or are yet to be completed. Furthermore, the mechanisms of how probiotics/prebiotics exert their effects are not completely clear, but some hypotheses hint at promising benefits, including immunological and nonimmunological roles.

Taking that all the above into consideration, it is generally thought that probiotics/prebiotics:

1) Enhance our immune defense system by increasing secretory IgA production (a type of leukocyte that makes antibodies to fight specific infections), tighten the mucosal (GI tract lining) barrier, enhance leukocyte cytokine (the protective chemicals released by antibodies) response, and enhance phagocytic activity (leukocytes eating bad guys).

2) Displace or antagonize pathogenic bacteria from colonizing our guts, by competing for attachment sites, or by fortifying the gut lining to prevent pathogen (like clostridium perfringens and salmonella) spread within the body.

3) By acidifying the colonic pH by producing fermentation byproducts like short-chain fatty acids, promoting several benefits.

4) Transforming and promoting the excretion of toxic substances like bile acids (reducing serum cholesterol), nitrosamines (carcinogens in cured meats),heterocyclic amines (carcinogens from meats cooked at high temperature), and mutagenic compounds.

5) By enhancing fecal bulk, speeding transit time, thereby lowering colonic exposure to toxic substances

Plain Talk About Legumes from a Chef’s Perspective

But you don’t necessarily need to know the scientific nomenclature or what the specific health benefits are; you just need to know where to find the health promoting foods in the produce aisle. Fermentable fibers can be found in peas and beans; like green beans, snap peas, soybeans, chickpeas, lentils; mung, lima, northern, navy and kidney beans; cranberry beans, butter beans , cannellini, adzuki, flageolets and fava beans; plus many, many other varieties. There are many other foods that are considered to be prebiotic including everything in the onion family, sunchoke (Jerusalem artichoke), globe artichoke, chicory root, burdock, dandelion greens, salsify; whole wheat, barley and rye. Eating legumes and the dietary fiber they contain is beneficial in other ways.

Eating legumes and the dietary fiber they contain is beneficial in other ways.

Dietary fiber has a tendency to slow the absorption rate of carbohydrate, which can help a person with diabetes mellitus to regulate blood glucose concentrations. It has been shown that a high fiber diet can lower serum cholesterol to acceptable levels, thereby mitigating the risk of heart disease.

Iacopi Farms Fava Beans at Home
Iacopi Farms Fava Beans at Home
Iacopi Farms Fava Beans at Home

 

In the fall, late August through mid-November, fresh beans in the pod can be found at many farmer’s markets and grocery stores. The beans pictured in this article are from Iacopi Farms of Half Moon Bay, and were purchased at my local farmer’s market. If your market does not carry them, ask for them. They are available in the wholesale marketplace so you just have to ask nicely and assert the demand. Chefs have long known the secret about freshly shucked beans: contrary to the bad press, they possess a delicate creamy vegetal flavor, and they can bring a rich decadence to a meal. My first boiled fresh butter bean was a revelation; the tissue-thin skin gave way to a whipped potato-like creamy interior, melting on my tongue. Try any freshly shucked bean sautéed in olive oil with late summer fresh corn cut off the cob, cippolini onion, garlic, and then add big chunks of heirloom tomato just before serving. I pair this ragout with grilled chicken or sautéed fish, but the mixture is a low fat, complete meal all by itself, made even better served with a slice of toasted levain.

References

Collins, S. M., & Bercik, P. (2009). The relationship between intestinal microbiota and the central nervous system in normal gastrointestinal function and disease. Gastroenterology136, 2003-2014. http://dx.doi.org/:10.1053/j.gastro.2009.01.075

Forchielli, M. L., & Walker, W. A. (2005). The role of gut-associated lymphoid tissues and mucosal defence. British Journal of Nutrition93(supplement 1), S41-S48.

Gropper, S. S., Smith, J. L., & Groff, J. L. (2009). Advanced nutrition and human metabolism (5th ed.). Belmont, CA: Wadsworth.

Lindemann, W.C., & Glover, C.R. (n.d.). Nitrogen fixation by legumes. Retrieved from New Mexico State University website: http://aces.nmsu.edu/pubs/_a/A129/

McGee, H. (1984). On food and cooking. New York, NY: Macmillan.

Schrezenmeir, J., & de Vrese, M. (2001). Probiotics, prebiotics, synbiotics–approaching a definition. American Journal of Clinical Nutrition73(suppl.), 361s-364s.

Tatum Hattner, J. A., & Anderes, S. (2009). Gut insight, probiotics and prebiotics for digestive health and well-being. Author.

United States Department of Agriculture, Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, Exec. Doc. No. 111-2010, 2d Sess. (2010).

U.S. Department of Agriculture, Agricultural Research Service. 2013. USDA National Nutrient Database for Standard Reference, Release 26. Nutrient Data Laboratory Home Page, http://www.ars.usda.gov/ba/bhnrc/ndl

Vighi, G., Marcucci, F., Sensi, L., Di Cara, G., & Frati, F. (2008). Allergy and the gastrointestinal system. The Journal of Translational Immunology, 153(Suppl.1), 3-6. http://dx.doi.org/10.1111/j.1365-2249.2008.03713.x

 

 

 

 

 

 

 

 

 

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