In praise of fibre
Fibre is making a dramatic comeback in our diets: we hear about it everywhere, even many commercial products are now labelled ‘rich in fibre’. But what is fibre? From a chemical standpoint, fibre consists mainly (but not exclusively) of complex carbohydrates, but carbohydrates which are very hard to absorb. Among those most commonly found in fibre are CELLULOSE, HEMICELLULOSE AND PECTIN1. Carbohydrates are molecules called polymers, that is, they are like long necklaces made up of many pearls called monomers. Specifically, the only monomer of which carbohydrates are made is glucose. Both cellulose and starch, for example, are polysaccharides made up only of long chains of glucose, but what makes these molecules different is the type of bond that joins the single glucose molecules together.
This subtle difference means that cellulose and starch have different functions both in the plant from which they are derived (starch serves as an energy reserve, whereas cellulose has a structural function) and in human nutrition. In the human gastro-intestinal tract there are protein structures, called enzymes, which are specifically designed to break down starch into its glucose units so that it can be absorbed. In contrast, humans (unlike strict herbivores) lack the enzymes needed to digest cellulose, so that it remains in one piece throughout its journey through the digestive tract. Cellulose, like the other carbohydrates and components present in fibre, is therefore indigestible. The body is unable to break down the components that make up fibre into its essential molecules, which are therefore not absorbed. Most fibre cannot be digested and absorbed. But if we cannot take full advantage of its nutrients, what are the benefits of fibre to the organism?
First of all, it is not entirely true that the fibre in our bodies is not exploited; although the cells that make up our tissues cannot use this substance, there are others that use it a great deal, namely the bacteria that live in our intestines (intestinal bacterial flora). Over the course of our lives, our intestines, which are sterile at birth, are gradually colonised by these organisms, of which it is estimated that there are more than 1,000 species, including the famous lactobacilli, and that there are more than 100 trillion of them in our bodies, which is about ten times more than the number of cells that make up our entire body. That really is a lot. Most of these bacteria are found in the colon, the final part of our intestines, because this area has several conditions that are optimal for the growth of these organisms. The presence of these bacteria in our intestines is very important because, together with the immune system, they prevent infection of the gastrointestinal tract by ‘enemy’ bacteria, that is, bacteria that could be harmful. These good bacteria are also able to produce certain vitamins, amino acids and keep the intestinal mucosa in good condition, so that digestion and then absorption of various nutrients is facilitated. The maintenance of intestinal flora is thus of fundamental importance for our organism.
First of all, it is not entirely true that the fibre in our bodies is not exploited; although the cells that make up our tissues cannot use this substance, there are others that use it a great deal, namely the bacteria that live in our intestines (intestinal bacterial flora). Over the course of our lives, our intestines, which are sterile at birth, are gradually colonised by these organisms, of which it is estimated that there are more than 1,000 species, including the famous lactobacilli, and that there are more than 100 trillion of them in our bodies, which is about ten times more than the number of cells that make up our entire body. That really is a lot. Most of these bacteria are found in the colon, the final part of our intestines, because this area has several conditions that are optimal for the growth of these organisms. The presence of these bacteria in our intestines is very important because, together with the immune system, they prevent infection of the gastrointestinal tract by ‘enemy’ bacteria, that is, bacteria that could be harmful. These good bacteria are also able to produce certain vitamins, amino acids and keep the intestinal mucosa in good condition, so that digestion and then absorption of various nutrients is facilitated. The maintenance of intestinal flora is thus of fundamental importance for our organism.
Key Facts
1. NOURISHES GOOD BACTERIAL FLORA
2. COUNTERACTS THE GROWTH OF BAD BACTERIA
3. RETAINS WATER IN THE COLON
4. PRODUCES BUTYRATES AND SUCCINATES (anti-cancer molecules)
5. LIMITS THE ABSORPTION OF SUGARS
6. AIDS INTESTINAL REGULARITY
7. FILLS YOU UP RAPIDLY TO HELP YOU STAY IN SHAPE
8. REGULATES GLYCAEMIA and CHOLESTEROL
9. IS A PRECIOUS FOOD FOR A HEALTHY COLON
10. IS FOUND IN ABUNDANCE IN SEASONAL VEGETABLES
2. COUNTERACTS THE GROWTH OF BAD BACTERIA
3. RETAINS WATER IN THE COLON
4. PRODUCES BUTYRATES AND SUCCINATES (anti-cancer molecules)
5. LIMITS THE ABSORPTION OF SUGARS
6. AIDS INTESTINAL REGULARITY
7. FILLS YOU UP RAPIDLY TO HELP YOU STAY IN SHAPE
8. REGULATES GLYCAEMIA and CHOLESTEROL
9. IS A PRECIOUS FOOD FOR A HEALTHY COLON
10. IS FOUND IN ABUNDANCE IN SEASONAL VEGETABLES