Do You Know the Importance of Properly Nourishing Not Only Our Bodies but Also the MICROBIOTA We Live With?

What Is the Microbiota?

The microbiota is an ecosystem that occupies an important place in the human body, mainly inhabiting the skin and gastrointestinal (stomach and intestinal) tract. It consists of microorganisms such as bacteria, viruses, fungi and protozoa, and functions like an organ. It is estimated that a person weighing 70 kilograms has approximately 1.5 kilograms of microbiome and that the beneficial microorganisms with which we coexist number more than 30 trillion.

Where Does the Microbiota Get Its Energy / How Is It Nourished?

The microbiota uses food components that reach the colon without being digested in the upper parts of the digestive tract as an energy source.

Which Carbohydrates Are Suitable for the Microbiota?

Carbohydrates, an important source of energy for the human body, consist of carbon, oxygen and hydrogen atoms. When carbohydrates are considered in 3 main groups (monosaccharides, disaccharides and polysaccharides), monosaccharides and disaccharides are called simple sugars because of their structures, while polysaccharides are called complex carbohydrates. Simple carbohydrates are completely absorbed in the small intestine, so they cannot reach the colon and are insufficient for nourishing the microbiota. Many complex carbohydrates resist digestive enzymes in the small intestine and therefore are not fully digested in the upper gastrointestinal tract, allowing them to reach the colon. Components that reach the colon are fermented by bacteria in the microbiota, producing short-chain fatty acids. The short-chain fatty acids produced by fermentation are propionate, butyrate and acetate. These fatty acids may improve health through their beneficial effects.

What Should We Do to Nourish the Microbiota Well?

The protective effects of microbiota diversity and balance against many diseases are now known. The reverse is also true: disruption of microbiota health and balance, known as intestinal dysbiosis, can open the door to many diseases, including colon cancer. To nourish the microbiota, we should benefit from the health-promoting effects of short-chain fatty acids. As mentioned above, it is now known that many polysaccharides are not digested in the upper digestive tract and enter the colon as a potential food source for the microbiota. However, until the late 1970s, the extent to which intestinal bacteria could metabolize dietary fiber was unknown. At that time, researchers conducted numerous studies to fill this gap and tested the ability of various anaerobic bacterial species in the human colon to ferment polysaccharides. By studying the fermentation of different polysaccharides by Bifidobacterium and Bacteriodes species, they found that intestinal strains have diverse and inducible abilities to break down different substrates.

The Relationship Between the Microbiota and Dietary Fiber

As the ability of intestinal bacteria to ferment polysaccharides became understood, research into the relationship between the microbiota and diet continued. Researchers then suggested that changing the availability of food sources in the diet (for example, restricting fiber intake) could trigger the activation of enzymes that break down the intestinal mucin layer (proteins found in the intestinal epithelium), affect human health and even colon cancer. However, until 2005, researchers had been unable to demonstrate the effects of dietary changes on the colonic microbiota in the human body. Subsequent research included many studies of the relationship between eating habits and the microbiota, and the desired results were obtained. In one study, researchers colonized the intestines of mice with bacteria-free intestines with Bacteroides thetaiotaomicron, a bacterial species of the genus Bacteroides that can ferment various substrates, and tested how different diets affected bacterial gene expression. They found that, in mice fed a diet rich in fiber, expression of B. thetaiotaomicron genes involved in polysaccharide metabolism increased significantly. Another study investigated the effects of dietary fiber consumption on microbiota diversity. Mice were randomly divided into 2 groups. One group was fed a low-fiber diet for 7 weeks, while mice in the control group received a high-fiber diet throughout the study. At the start, the microbiota composition of the 2 groups was indistinguishable. After the dietary composition was changed, the mice that began eating a low-fiber diet started to show unfavorable changes in microbiota composition and diversity compared with the control group. In conclusion, studies investigating the relationship between dietary fiber and the microbiota have found that:

• Dietary fiber nourishes intestinal bacteria and plays an important role in shaping the microbial ecosystem;
• Dietary changes can substantially affect the microbiota;
• Carbohydrates that resist digestion in the intestinal tract and are fermented by the microbiota in the colon (such as resistant starch) may improve human health by supporting the production of short-chain fatty acids.