…modern societies consume highly processed foods that are digestible and absorbed mainly in the small intestine and are ignorant of the value inherent in consuming fibres that do not have direct appeal in fad diets. This begs the question: What is dietary fibre and why is it important?
It did not make headlines then and if I told you that the United Nations declared 2021 as “International Year of Fruits and Vegetables”, your plausible response, as you read this, is probably, ‘who cares?’ This attitude, for good reason, would be the natural reaction if someone translates this same message to Yoruba language in the village where I had my primary school education. Of course, it would come off redundant because eating fruits, vegetables and starchy foods is the way of life, depending on the season. It just happens that the most important things in life are least appreciated: Life is supported by energy extraction from ingested foods, but we need oxygen to obtain this chemical energy, not only to support life itself but for growth and reproduction. Now, if some silly world entity declares 2021 as the International Year of Oxygen, the predictable reactions would equally be, ‘who cares?’ No one would certainly care, not because food is more important than oxygen but there is oxygen everywhere, and freely too. In that case, there is no value in such silly declaration about the importance of oxygen. However, to a few astronauts who inhabit the International Space Centre and have to “harvest” oxygen via electricity and water, that laughable declaration on earth may not sound so ridiculous, as long as they stay up there in a tightly enclosed capsule about 254 miles above the earth.
While the encouragement to consume fruits and vegetables was not directed to anyone in my former village or any rural dweller in developing countries, most people in the Western world and urban centres do not care because of the obsession with calorie counting and, more importantly, dietary fibre found in fruits and vegetables is not considered a macronutrient and doesn’t fit into calorie consciousness. Therefore, modern societies consume highly processed foods that are digestible and absorbed mainly in the small intestine and are ignorant of the value inherent in consuming fibres that do not have direct appeal in fad diets. This begs the question: What is dietary fibre and why is it important?
Dietary fibre can be soluble or insoluble. Generally, soluble or fermentable fibre transforms into thick viscous syrup, which helps to delay the stomach emptying into the small intestine and thus stimulates a sense of fullness and satiety.
Dietary fibre is defined as part of a plant’s components that cannot be completely broken down by the human digestive enzymes. In other words, dietary fibre is that part of the food that travels the entire 22 feet long small intestine, where almost all digestion and absorption take place, but still retains its integrity, as it arrives in the large intestine intact. Dietary fibres found in fruits and vegetables are a mix of starch and cellulose. While we can enjoy free glucose molecules in honey, fruit juices and all forms of colourful modern sugary drinks, glucose units are arranged or “stacked” tightly together in several thousands to form dietary fibre that resists human digestive enzymes to give up its glucose. As one writer puts it, you can use pieces of wood to make a chair, reading table or build a wooden house, and it is still wood. In the same way, glucose units can be arranged differently to form starch or tightly packed to form insoluble and non-digestible fibrous carbohydrates found in all plants, including vegetables/fruits, grass, woods, cotton, etc. While humans have no digestive enzymes to extract glucose from woods like termites and cannot consume grass like the herbivores, with a specialised stomach or four-chambered stomachs, we still need some amounts of fibre in our diet to support the ecology of trillions of gut bacteria which are in a symbiotic relationship with our digestive system and by extension, our overall health.
Dietary fibre can be soluble or insoluble. Generally, soluble or fermentable fibre transforms into thick viscous syrup, which helps to delay the stomach emptying into the small intestine and thus stimulates a sense of fullness and satiety. This sense of fullness explains why some Nigerian meals are called “So’ku da’le” in Yoruba language, which loosely translates to “hold back hunger till sunset”. With those kind of meals, who needs snacks? The gel like viscous property of soluble fibre also reduces the absorption of sugar and controls the reabsorption of cholesterol from bile salts secreted into the small intestine by the liver. In the large intestine, the insoluble or non-fermentable fibre provides bulk and absorbs water to increase fecal weight and promote regularity. However, the gut bacteria degrade soluble fibre via fermentation to increase its population and diversity. The bioactive products of fermentation, such as short chain fatty acids are the main source of energy for the cell lining of the large intestine, which, in turn, produce a dense mucus wall that separates the gut bacteria from the lining of the large intestine. The gut bacteria thrive on the outer part of this wall, which contains food materials, and the inner layer of the mucus wall is protectively bacteria free.
…the consumption of processed foods has been linked to the breaching of this mucus wall because in the absence of dietary fibre, the gut bacteria have metabolic flexibility to feed on the mucus wall that separates them from the intestinal lining.
However, the consumption of processed foods has been linked to the breaching of this mucus wall because in the absence of dietary fibre, the gut bacteria have metabolic flexibility to feed on the mucus wall that separates them from the intestinal lining. A compromised mucus wall may lead to infection and systemic inflammation and has been linked to irritable bowel syndrome, Crohn’s disease, type 2 diabetes and colon cancer. As one author noted, “the gut bacteria will feed on you if you don’t feed them”. To reinforce the message again, 2021 is the International Year of Fruits and Vegetables. You should care.
Mukaila Kareem, a doctor of physiotherapy and physical activity advocate, writes from the U.S.A and can be reached through firstname.lastname@example.org