What IS fibre, exactly?
Fibre is a ‘non starch polysaccharide’ – basically, it consists of lots of sugar molecules joined together. It is a subtype of carbohydrates which humans cannot break down (digest) because we do not have the required cellulytic enzymes in order to break the specific bonds between the molecules.
So, why is it important for us then if we cant even digest it? Well, fibre is actually really beneficial for us in a plethora of ways.
There are 2 main types of fibre:
• Soluble fibre- dissolves in water forming a gel like substance found in oat, bran, nuts, seeds, beans and lentils amongst other things, too.
• Insoluble fibre- does NOT dissolve in water, instead it absorbs water and increases the bulk of stools. It’s found in abundance in wholegrain bread, cereals, wheat bran and the skin of fruits and veggies.
We all know fibre is good for us but does anyone ever question WHY this is? Lets investigate some physiological effects and properties of fibre..
• What happens when we ingest fibre?
Fibre remains undigested and travels through the GI (digestive tract) all the way to our colon (large intestine) where our beneficial bacteria (the microbiome) metabolise it (break it down). FUN FACT: there are 10x more bacterial cells in the intestine of humans than there are human cells in the WHOLE body. Gut bacteria LOVE fibre: it’s their primary food source (known as a PRO- biotic: it feeds the microbiome). Bacteria start metabolising the undigested fibre via fermentation processes because they have the appropriate enzymes that us as humans don’t have. A by-product of this fermentation process is the production of short chain fatty acids (SCFA’s). These SCFA’s are taken up by the colonocytes (colon cells) and nourish the cells. Fibre feeds our gut bugs, keeping them satisfied and in return they feed our colonic cells with fatty acids. What a lovely, reciprocal + symbiotic relationship!
One of the fatty acids produced is called butyric acid- which increases something called beta oxidation (burning) of body fat meaning that fibre could well be really beneficial in healthy weight maintenance/ weight loss.
The SCFA’s also encourage release of certain molecules into the blood from the intestine which trigger feelings of satiety (fullness) meaning fibre promotes a feeling of fullness- meaning it is an excellent tool in weight control/ management.
Health claims of fibre rich foods:
You may have noticed on packs of oats that companies such as Quaker make health claims related to CHOLESTEROL: something similar to ‘clinically proven to decrease cholesterol’. This is a claim that is backed up by science and a sound body of evidence. Fibre can actively decrease cholesterol levels within the body. In order to optimally digest fats, something called bile is needed to break up and emulsify fats in the stomach. An important component of bile is the cholesterol molecule. Bile is recycled within the body via a pathway including the liver and intestines, but when dietary fibre is present it binds with the circulating cholesterol whereby disrupting the pathway and leading to the excretion of the cholesterol and fibre from the body. Any excess cholesterol in the body is recruited by the liver to make more bile because that bile has been excreted. This all lowers total cholesterol levels.
Fibre also prevents absorption of dietary cholesterol (plant sterols bind to cholesterol). This means that fibre can be really rather beneficial for heart health and help decrease chances of developing CVD (cardiovascular disease).
Sadly, despite the amazing health benefits of fibre, most people do not get anywhere near enough. We should aim for 15g fibre per 1000calories we consume. However following weight loss surgery your calorie intake is reduced so it is a good idea to have a fibre rich diet to ensure your body is getting enough. In order to help you increase your fibre intake: try and aim for 5 portions of fruits/ veggies a day, choose wholegrain options wherever possible (brown rice, brown pasta, brown bread), have things like bran flakes for breakfast (a portion provides 5g fibre) or porridge for breakfast. Snack on things like nuts, seeds and a little dried fruit for a fibre rich snack between meals.
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