What's the Fuss Over Fibre?
by Sarah Ann Macklin, ANtur.
WHAT’S THE DEAL WITH DIETARY FIBRE?
Fibre is not spoken about enough! There are so many health benefits to this Cinderella nutrient.
WHAT IS DIETARY FIBRE?
Fibre is one nutrient that you are hearing a lot of recently, and for good reason. It has been linked to improving heart health, type 2 diabetes, immune health, mental wellbeing as well as our digestive health, but what exactly is it?
Fibre is a non-digestible complex carbohydrate found in plant foods, which are not digested in the small intestine (like sugars and starches), reaching our large intestine and colon.
WHAT ARE THE DIFFERENCE TYPES OF FIBRE?
All plant based foods provide fibre and there are thought to be over a 100 different types! Fiber’s diversity ranges in each type of plant based source, as each type has a different structure.
There has been much debate about the terms ‘soluble’ and insoluble’ fibre, although these terms are not used much among scientific organisations today, because most plant sources usually contain both.
Soluble fibre dissolves in the stomach into a gel like substance, slowing down the emptying process, allowing you to feel fuller for longer and stabilising blood sugar levels. Soluble fibre also includes pectins (structural fibre found in primary cell walls) and beta-glucans (found in fruits and oats) both which have health benefits including lowering cholesterol and improving heart health.(1)
Insoluble fibre absorbs water to provide a bulk and moisture to stools which helps to relieve constipation and improve overall bowel health. Insoluble fibre also includes cellulose (found in whole grains and nuts), which helps plants to remain stiff.
Resistant starch (RS) is a form of starch which cannot be digested in the small intestine (2). It is fermented in the small intestine and helps produce small chain fatty acids (SCFA). This provides an energy source for our microbes!
WHY IS FIBRE IMPORTANT?
Understanding the mechanisms that link fibre-rich food to good health is challenging. Dietary fibre encompasses a wide range of complex molecules, most of which are present in plant cells; among them are carbohydrate molecules called glycans, which are resistant to digestion by human enzymes. However, it is important to include a diverse range of plant based food as all fibre is different.
Research into fibre has shown benefits which are associated with a lower risk of cardiovascular disease (3), blood pressure, diabetes (4), some cancers, weight management (5) and immune health (6). However, these fibres haven’t showed as strong evidence for the gut microbiome. New research shows, that prebiotic fibre increases the number of good bacteria in our digestive system by feeding them.
Foods such as oats and barley contain a type of fibre known as beta glucan, which may help to reduce cholesterol levels if you consume 3g or more of it daily (4).
Fibre rich diets generally tend to have a lower energy density and low glycemic index (this helps maintain a stable blood sugar). These qualities of fibre help support other health outcomes too.
HOW MUCH FIBRE DO WE NEED?
Due to the large health benefits of fibre, our recommended daily intake was increased in 2015 by the Scientific Committee on Nutrition (SCAN), to 30g a day for adults between 17years and over.
In the UK, we currently only reach between 15-19g/d and fall very far behind the recommended daily requirement. Diets such as the Mediterranean diet consume up to 50g/d of fibre, due to a large part of their diet make up of plant based sources. I believe we should be aiming for more of this level due to the benefits that fibre brings to every part of our body; from immune, brain, heart, digestive and mental health.
If you are increasing your fibre, please do it gradually and build it up, whilst consuming plenty of water. Increasing a high fibrous diet very quickly can increase certain gastrointestinal issues, such as bloating or cramping whilst your body adapts.
Table to show fibre intake for age groups
AGE (YEARS) RECOMMENDED INTAKE OF FIBRE
2-5 15g per day
5-11 20g per day
11-16 25g per day
17 and over 30g per day
Source SCAN carbohydrates report 2015
FOOD LABELLING
You may have noticed that there isn’t always clear labelling on dietary fibre. I hope soon this may change, as I believe more awareness needs to be made to increase our daily dietary fibre, due to our current intake which is very low. It is important to be aware many labels may be marketing a high fibre product which may not be high in fibre at all.
According to Regulation (EC) No 1924/2006 (EC 2006), nutrition claims are permitted for fibre as below:
Source of fibre: 'A claim that a food is a source of fibre, and any claim likely to have the same meaning for the consumer, can only be made where the product contains at least 3 g of fibre per 100 g or at least 1.5 g of fibre per 100 kcal'
High in fibre: 'A claim that a food is high in fibre, and any claim likely to have the same meaning for the consumer, can only be made where the product contains at least 6 g of fibre per 100 g or at least 3 g of fibre per 100 kcal'
FIBRE RICH FOODS
All plant based foods will contain fibre, which is why increasing your intake of plant based sources is so important. Below are a list of some key fibre foods:
General fibre
· Vegetables (especially leafy greens, broccoli, carrots, peas, potatoes (skin on) and sweetcorn)
· Legumes (chickpeas, red kidney beans, lentils, spilt peas, black beans)
· Fruits (especially berries, pears, melon, apples and bananas)
· Oats, barley, wholegrains, rye, whole-wheat pasta
Prebiotic fibre
· Chicory root
· Artichoke
· Onion
· Garlic
· Wheat flour
· Beans and lentils
WHY CAN FIBRE GIVE ME WIND?
Dramatically increasing to a fibrous diet quickly can give some people bloating and flatulence. To avoid this, gradually increase your fibre intake, making small changes to allow your body to adjust. This can be adding in a handful of almonds or, making simple swaps from white crumpets to porridge for your breakfast in the morning.
Fibre absorbs fluid, therefore make sure you are always drinking enough water and fluids throughout the day. Make sure these aren’t fizzy drinks!
FIBRE AND DIGESTIVE HEALTH
Apart from helping maintain regular bowel movements, some fibre foods contain prebiotics which help to ‘feed’ the beneficial bacteria which live in our digestive tracks.
DIVERSITY IS KEY, especially when it comes to helping out gut microbes.
A recent study of 40 healthy individuals from the UK, who normally ate 18g/d of fibre were given different type of resistant starch for 4 weeks (corn, potato, tapioca or placebo). Participants increased their dose of fibre on top of their previous 18g/d. Week one was an extra 10g/d, week 2 20g/d, week 3 35g/d and week 4 50g/d.
Results?
Having more than 20g a day of the SAME type of fibre, showed a decrease in the gut microbiota diversity!
Secondly, Tim Spector who leads the field in the gut microbiome research in identical twins, has released new findings, to see how the human gut can play a role in obesity. He looked at body weight change over time and the gut microbiome composition of fecal samples from 1632 healthy females from the TwinsUK.
Results?
Those who had a higher gut microbiome diversity was negatively associated with long term weight gain, whilst it was positively correlated with fibre intake. So the diversity of plant based foods you are eating, will play a part in your weight loss! (8)
References
(1) Boyer, J. and Liu, R., 2004. Apple phytochemicals and their health benefits. Nutrition Journal, 3(1).
(2) British Nutrition Foundation. 2020. [online] Available at: <https://www.nutrition.org.uk/healthyliving/basics/fibre.html?start=1> [Accessed 5 May 2020].
(6) Menni, C., Jackson, M., Pallister, T., Steves, C., Spector, T. and Valdes, A., 2017. Gut microbiome diversity and high-fibre intake are related to lower long-term weight gain. International Journal of Obesity, 41(7), pp.1099-1105.
(7) Kcl.ac.uk. 2020. Some Types Of Fibre More Beneficial For Gut Health Than Others. [online] Available at: <https://www.kcl.ac.uk/news/some-types-of-fibre-more-beneficial-for-gut-health-than-others> [Accessed 5 May 2020].
(8) Berer, K., Martínez, I., Walker, A., Kunkel, B., Schmitt-Kopplin, P., Walter, J. and Krishnamoorthy, G., 2018. Dietary non-fermentable fiber prevents autoimmune neurological disease by changing gut metabolic and immune status. Scientific Reports, 8(1).