The torturers went on to inform me of the importance of fibre in the daily diet as a crucial aid in the goal of keeping well. I declined the prune juice, asked where the bathroom was (an appropriate ruse I thought) and got out of there quicker than you can say "flush". Perhaps this tendency to discuss bowel habits and their link to health has a genetic link and I've inherited the proclivity, as I now find myself subjecting perfect strangers to the very same torture every day at work as we discuss their various ills and remedies.
Clearly, the idea that a high fibre diet might be good for you is nothing new. But, like a lot of things, our understanding of exactly how fibre is good for you and what benefits you can obtain by eating a diet laden with fibre-rich foods has changed a lot since I was a kid.
Back in my school days, when I was downing my brown bread sandwiches, my primary understanding of fibre's role was that it kept you regular. It still does fulfil that function, but just how fibre improves our health is one of the more widely researched, accepted and promoted areas of healthcare today. And yet most people are still well below the daily intake target of at least 25 grams each day for an adult.
The list of fibres includes soluble and insoluble fibres, along with an indigestible form of starch, which was discovered to have fibre-like properties and is known as resistant starch (because it resists digestion).
Subgroups of fibre you may have come across are cellulose and hemicelluloses, mucilages, pectins, gums and lignins. Each one of these types of fibre is extremely good for your health, with different properties and health promoting aspects for each, with some overlap between them all.
It should be no surprise to note that a diet rich in fibre can reduce cardiovascular disease, given that fibre is found only in food of plant origin, such as fruits, vegetables, nuts, seeds, legumes, herbs, spices, and whole grains. Such foods have provided significant evidence for reducing cardiovascular disease risk and much of the benefit can be attributed to the fibre content of these foods.
Evidence suggests that fibre achieves this through different mechanisms, including inhibiting intestinal absorption of cholesterol, slowing blood sugar elevation following carbohydrate ingestion and by inducing fullness, which inhibits the appetite, thus promoting weight loss. It is easy to see how simple old fibre can contribute to a reduced risk by helping you control your cholesterol, blood sugar and weight. All this and better bowel movements too!
Acting as a prebiotic, fibre has the ability to feed the trillions of probiotic colonies (beneficial bacteria) in your bowels. These bacteria ferment the fibre and produce certain volatile fatty acids such as butyric, acetic and propionic acids. These acids have various beneficial effects, including supporting the bowel mucosal wall. Increased production of butyric acid may also reduce your risk of developing colorectal cancer and inflammatory bowel diseases.
When increasing your dietary fibre intake you can expect to initially notice a subsequent surge in your production of bowel gas. This is a totally normal result of the fermentation of the fibres by your colonies of bowel bacteria. This usually settles to a normal and comfortable level in a short time and is of little consequence considering the many benefits that fibre provides to your health. Occasionally, some people will suffer from pain and cramps if they increase their fibre intake too quickly and their bowels cannot cope with the change. The ability to break down fibre seems to vary considerably from person to person and depends greatly upon the types of bacteria we each carry in our bowels.
Increasing your fibre intake feeds up your bacteria and helps you develop a more robust intestinal ecosystem - but it's best not to rush it.
A considerable amount of your stool bulk is made up of bacteria from the bowel, which have multiplied as they process the food you couldn't. For this reason, eating more fibre consistently will tend to significantly increase the size of your stools compared to when you had a lower fibre intake.
As adults, we should be aiming to include at least 25 grams of fibre in our diet each day. Most people are falling well short of this target, but with a little attention to eating a less processed diet this amount is easily achievable.
Good health, Jeremy.