Your gut microbiome influences immune function (and beans keep it healthy) by Joel Fuhrman, MD

Why beans?

Beans, lentils, and split peas are rich in fiber, resistant starch, and plant protein, and they are a low-glycemic carbohydrate source. The health benefits of these legumes sometimes get overlooked, but adding beans to your diet promotes weight loss, cardiovascular health, and insulin sensitivity.

Related post: Clinical study confirms that beans are the preferred starch source for diabetics

What is the microbiome?

The human microbiome is a complex collection of bacteria, viruses, fungi, and other microorganisms that inhabit body surfaces, including the skin and digestive tract. The majority of the microbiome lives in the gut, where there are more than 1000 different species of bacteria.

The gut microbiome in action

The trillions of organisms in the gut microbiome are busy: They produce vitamins, such as K2 and B12, help develop immunity, enhance the benefits of some phytochemicals, and protect against pathogens. The bacteria of the microbiome converts dietary fiber and resistant starch from plant foods into short-chain fatty acids (SCFAs) that protect intestinal cells and regulate metabolism.1-4 The gut microbiome can even be considered an organ of the human body; without it, the body would not function properly.

Sources:

Harvard T.H. Chan School of Public Health: The Microbiome
What is the microbiome?
Gut microbiota functions: metabolism of nutrients and other food components.
Interaction of dietary compounds, especially polyphenols, with the intestinal microbiota: a review.
Starving our microbial self: the deleterious consequences of a diet deficient in microbiota-accessible carbohydrates.
Diet-microbiota interactions as moderators of human metabolism.

Intestinal immune function is largely shaped by the microbiome

The intestinal mucosal immune system is a large and important part of the whole human immune system, and the microbiome is closely connected with intestinal immunity. The microbiome modulates the activity of immune cells, counteracts inflammation, and maintains the integrity of the intestinal barrier.5-7 This means we count on a healthy gut for a powerful immune response.

Sources:

Interaction between the gut microbiome and mucosal immune system.
The microbiome and regulation of mucosal immunity.
Human nutrition, the gut microbiome and the immune system.

What makes beans special?

Beans, lentils, split peas, and other legumes are rich in fiber and resistant starch, carbohydrates that cannot be broken down by human digestive enzymes.

The bacteria that reside in the large intestine depend on “microbiota-accessible carbohydrates,” also known as prebiotics, to survive; prebiotics are food for gut bacteria. Without enough prebiotics in our diet, gut bacteria begin to consume an alternative energy source: the first line of our immune defense on the surface of the intestinal lining. This intestinal lining is made up of molecules called mucins.3

All plant foods contain some prebiotics, but beans are special because they are very high in resistant starch, making them especially rich in prebiotics. Not all indigestible plant carbohydrates act as prebiotics, but resistant starch from beans provides large amounts of prebiotics. Prebiotics nourish the microbiome and allow for production of SCFAs.3

So the fiber and resistant starches from beans are waiting in our digestive tract and full of microbiota-accessible carbohydrates. To sum it up, we eat beans because they nourish our microbiome and  promote production of short chain fatty acids. SCFAs help kick our immune system into gear.

What’s a SCFA? (Continue reading …)

Source: Your gut microbiome influences immune function (and beans keep it healthy)