Have you ever stocked up on high-fibre foods to help your digestion, only to feel bloated and gassy? You are far from alone. In my practice as a registered nutritionist, clients often tell me they are confused by terms like soluble fibre, insoluble fibre, prebiotics and probiotics. Food marketing often uses them interchangeably, but they do different jobs.
The Difference Between Fibre and Prebiotics
To put it simply, all prebiotics are fibre, but not all fibre is a prebiotic. Dietary fibre is a broad term for the carbohydrates in plant foods that your body does not digest. Insoluble fibre, found in wheat bran and wholegrains, adds bulk to your stool and helps food move through. Soluble fibre, found in oats and pulses, absorbs water and forms a gel-like texture.
Prebiotics are a specialised group of fermentable fibres that act as fuel for the beneficial bacteria in your large intestine. When those bacteria ferment prebiotics, they produce short-chain fatty acids such as butyrate, acetate and propionate. Research suggests these may support the gut barrier and overall gut health. You can read more about how microbes influence your wider health in my overview of gut health.
Why Different Fibres Matter
Most adults in the UK eat less fibre than recommended, so for many people the first step is simply to eat more of it. But different gut bacteria thrive on different fibres, such as fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS) and inulin. A varied diet that includes both general fibre and prebiotic-rich foods tends to feed a wider range of bacteria.
If you have read my guide on probiotics vs prebiotics, you will know that live bacteria and the fibre that feeds them work as a team.
Because prebiotic foods are fermentable, they can cause extra wind in sensitive people. I work alongside your doctor on any diagnosed gut condition, and I would always want you to see them if you notice blood in your stool, unexplained weight loss, anaemia, a lasting change in bowel habit, or new digestive symptoms over the age of 50.
Everyday Food Sources
Rather than relying on supplements, I encourage getting these from food, because a diverse, plant-rich diet gives your gut a much wider range of fibres.
- Garlic and onions: Sources of inulin and FOS. Cooking them gently in stews still counts.
- Slightly green bananas: Contain resistant starch, which ferments in the large intestine.
- Leeks and asparagus: Soluble prebiotic fibres that add variety to meals.
- Oats and barley: Sources of beta-glucan fibre.
- Flaxseeds and chia seeds: A mix of soluble fibre and healthy fats that are easy to add to porridge or yoghurt.
- Chicory root and Jerusalem artichokes: Among the richest natural sources of inulin, so go gently.
Adding Prebiotics Comfortably
When clients come to my online consultancy keen to boost their gut health, their first instinct is often to add a lot of prebiotic food overnight. Doing it quickly can cause extra gas and cramps. If you are prone to bloating, see my tips on reducing bloating naturally first.
A gentler way is to add one new prebiotic food every few days and to drink plenty of fluid as you go, since fibre needs water to pass through comfortably. Pairing small portions with balanced meals is another way to ease in. If you are working on increasing your daily fibre intake, the same slow approach applies.
You can check your current intake with this UK fibre calculator.
If you would like an easy way to add variety to your plate, read my guide to eating 30 plants a week.
Personalised Gut Support
If adding chicory root or raw leeks leaves you feeling uncomfortable, generic high-fibre advice may not suit your gut at the moment. Everyone's tolerance is different, and finding the types and amounts of fibre that suit you is a matter of gradual, personal adjustment.
If you would like help expanding your plant variety in a way that suits you, explore my one-to-one support on my services page or use my contact page to book an online consultation.
