'What's more important: soluble or insoluble digestive fibre?'
The Expert: Ariana Rodriguez, registered dietitian and co-founder of Embody Health London
If you’ve ever sat through a cereal advert – particularly one from the early 00s – somewhere in your memory bank you’ll have a catchy tune or slogan that, to this day, reminds you fibre is an important part of a healthy diet. ('Plump and juicy raisins', anyone?)
Jaunty adverts aside, though, most of us grew up with very little guidance on essential nutrients – fibre included – so it makes sense that we still have uncertainties in adulthood.
A diet high in fibre is associated with a lowered risk of serious illness. The NHS recommends a daily intake of 30g fibre per day for adults for optimal wellbeing, which seems straightforward enough.
However, things get more complicated when you consider there are two main types of fibre – soluble and insoluble. So, which is more important for healthy digestion?
We spoke to Ariana Rodriguez, registered dietitian and co-founder of Embody Health London, to get to the bottom (sorry) of which type of fibre is the most essential, and find out how to get more of it in your diet…
What’s the difference between soluble and insoluble fibre, and which is more important for digestive health?
Dietary fibre is an essential nutrient derived from plant-based foods that is resistant to absorption and digestion by the digestive track, according to Rodriguez. ‘Instead, it is broken down and digested by bacteria that live in the intestines and utilised for fuel to maintain a healthy gut microbiome.’
Originally, it was thought that fibre’s prime purpose was to support bowel health by facilitating smooth and regular bowel movements and preventing constipation.
‘Research now shows us that in addition to this, an adequate intake of dietary fibre improves heart health through improved blood pressure and cholesterol levels, and it lowers the risk of diabetes and colon cancer,’ says Rodriguez.
‘More recently, we know that sufficient fibre intake supports immune function via the gut microbiome and can improve our mood through serotonin production that majorly takes place in the gut.’
So, what's the difference between the two types of fibre? Simply, one dissolves in water whilst the other doesn’t and, therefore, each has a slightly different function for optimal digestive health.
‘Soluble fibre is able to dissolve in water and thus becomes gel-like when digested,’ says Rodriguez. ‘It has been specifically found to improve blood pressure, cholesterol levels and blood sugar regulation. This includes plant gums and pectins.’
So, you guessed it, insoluble fibre does not dissolve in water. 'It's more ‘rough’ in that the structure remains intact when digested,’ says Rodriguez. 'It's responsible for drawing water into the colon via osmosis to soften stools, which in turn helps ease bowel movements and maintain regularity. This includes cellulose and hemicellulose.’
Unsurprisingly, both types of fibre are equally important as each works together to aid digestive wellbeing. So, there’s no need to track your intake of soluble and insoluble fibre separately – instead, focus on hitting the daily recommended amount of fibre in your diet.
What are the best sources of fibre?
A healthy diet should contain both soluble and insoluble fibre – and there are loads of affordable and easily-accessible sources to help you hit your 30g a day (no, you won’t need to hit the health food store).
Sources of soluble fibre include:
- Oats
- Psyllium
- Beans
- Apples
- Peas
- Avocado
- Flaxseeds
- Chia seeds
- Citrus fruits
- Seeds
- Grains
Sources of insoluble fibre include:
- Oat bran
- Wheat bran
- Whole wheat flour
- Nuts
- Vegetables, such as potatoes, green beans, and cauliflower
How can I increase my fibre intake?
Recent stats show that in the UK, the average fibre intake for adults is 60% (18g) of the daily recommended amount (30g). Want to boost your soluble and insoluble fibre intake? Try:
- Opt for smoothies over juices. ‘The challenge with juicing fruits and vegetables is the loss of fibre as they are left behind in the juice machine, while the other nutrients and water are extracted,’ says Rodriguez. Instead, blend and consume whole fruits and veggies.
- Add fruits and seeds to your breakfast. ‘1 tbsp flaxseeds added to your porridge, breakfast cereal or smoothie is ideal,’ says Rodriguez
- Eat oat-based cereal bars or nuts as snacks.
- Aim to make at least half of your grains come from wholemeal sources, such as breads and pastas.
- Leave the skin on vegetables and fruits instead of peeling.
- Add beans, chickpeas or pulses to meals.
- Fill half of your plate with vegetables at mealtimes as often as possible.
- Add spinach or frozen veggies to sauces or recipes such as curries and chillis.
- Drink ~2L of water per day whilst increasing fibre intake. ‘Increased fibre intake and insufficient hydration can lead to constipation – the opposite of what we want,’ says Rodriguez.
