Talking About Fibre
Let’s talk about your bowels. How regular are you? Do you have any concerns with how things are working? Knowing about the importance of dietary fibre might help solve some or all of your problems, or perhaps just improve things a bit….
Aren’t there different types of fibre?
That’s correct, there are several types of dietary fibre and these are present in different amounts in various plant foods. Each type of fibre plays an important role in ensuring our wellbeing. It’s worth noting that in general, highly processed foods tend to contain little if any fibre and more often contain high levels of added sugar and fat.
What is dietary fibre?
Dietary fibre is found in plant foods such as fruit, vegetables and cereals. It’s indigestible and passes relatively unchanged through our stomach and intestines (gastrointestinal system). Dietary fibre is sometimes referred to as ‘bulk’ and ‘roughage’, terms which are misleading since some forms of fibre are water soluble and are not bulky or rough.
Soluble fibre includes pectin, gums and mucilage. It’s found in fruits, oat bran, barley, beans, lentils, peas, soy milk and soy products. Even though soluble fibre can’t be digested, it absorbs water to become a gelatinous substance which bulks up the faeces, helping them pass through the body preventing constipation. Soluble fibre helps to reduce LDL cholesterol (‘bad’ cholesterol).
Insoluble fibre includes cellulose, hemicellulose and lignin located in plant cell walls. Insoluble fibre is found in wheat bran, corn bran and rice bran, dried beans, nuts, seeds and wholegrain foods, as well as the skins of fruit and vegetables. This form of fibre remains mostly unchanged as it transits through the body and adds bulk to the faeces, helping us to pass a bowel motion. Most plant foods contain both soluble and insoluble fibre.
Resistant starch also referred to as fermentable fibre, comprises around 10% of starchy foods. It’s found in lentils, peas, beans, unprocessed cereals and grains, as well as unripe bananas, cooled potatoes and cold pasta salad. Resistant starch, in the form of Hi-Maize, can be added to breads and breakfast cereals. Certain cooking processes and snap freezing lead to the formation of resistant starch in food. Resistant starch escapes digestion in the small intestine and is fermented in the large intestine by bacteria.
Why is fibre important?
Dietary fibre helps keep our digestive system healthy and assists with our overall health and wellbeing. People who do not have an adequate fibre intake tend to have poorly functioning digestive systems and may be at greater risk of certain health problems. Countries with traditionally high fibre diets commonly experience low rates of bowel cancer, diabetes and coronary heart disease.
People who eat diets with adequate amounts of fibre tend to have lower rates of obesity, type 2 diabetes, heart disease and bowel cancer. Adequate fibre intake is also thought to help stabilise blood glucose and cholesterol levels. Many people regularly don’t get enough fibre in their diet, especially those eating a predominately western style diet.
What are the benefits of resistant starch?
Like other forms of fibre, resistant starch is not broken down in the small intestine, however good bacteria in the large bowel ferment resistant starch to make short chain fatty acids. These provide energy to the cells lining the large intestine and ensure their wellbeing. Eating resistant starch improves insulin sensitivity, lowers blood sugar levels, reduces appetite and offers other digestive benefits, such as positive bowel changes, that may protect against the damage which precedes the development of bowel cancer.
What happens if you don’t consume enough dietary fibre?
A number of problems are associated with low fibre diets. These include constipation, which can lead haemorrhoids (varicose veins in the anus) from straining to have a bowel movement. Low fibre diets, particularly in animal studies, have been associated with diverticulosis, which is the formation of abnormal pouches in the bowel wall which can became inflamed or infected. Other conditions associated with low fibre diets include irritable bowel syndrome, overweight/obesity as well as coronary heart disease, diabetes and colon cancer.
How much fibre should I consume each day?
Experts recommend adults consume around 25 to 30 grams of fibre a day. This can be achieved by eating wholegrains (eg breads, brown rice, breakfast cereals with oats, barely or wheat), fruit (2 serves a day) and vegetables (5 or more serves a day), as well as legumes.
Exceeding recommended fibre intake levels is not recommended. Fibre intakes of 40g a day or more can lead to a reduction in the absorption of key minerals such as iron, zinc and calcium potentially leading to medical problems (eg reduced iron absorption can lead to iron deficiency anaemia).
Any final words?
If you want to include more fibre in your diet, increase the fibre content slowly to avoid abdominal problems and increased flatulence (wind). Having said that it’s important to note that the more fibre we eat the more wind we produce, which this is perfectly normal. Since dietary fibre absorbs fluid as discussed earlier, it’s important to ensure that your fluid intake is good. A useful way of tracking fluids and hydration, is to aim for urine that is a pale straw colour to clear, rather than yellow (except for first thing in the morning). Lastly, as we get older our digestive system slows down, meaning that a high fibre diet becomes even more important in order to maintain a healthy gut.