Fibre & Gut Health: What I Wish I'd Known When I Was Diagnosed With Crohn's Disease
When I was diagnosed with Crohn's disease, the standard advice was to avoid fibre. I understood the logic at the time, that an inflamed digestive system can't handle roughage. But what nobody gave me alongside that advice was any sense of what to do next, or what a healthy relationship with fibre might actually look like once things settled down.
In the years before I retrained as a Nutritional Therapist, I did what most people do and tried different things I came across online, including a full year of eating vegan, which as it turns out is about as high-fibre as it gets. For me personally, it was the worst thing I could have done. My already compromised digestive system couldn't handle the volume, and I ended up developing SIBO, small intestinal bacterial overgrowth, which is exactly what it sounds like. An overgrowth of bacteria in the small intestine who are having a field day eating all the fibre you're giving them, producing so much gas and bloating in the process that I was getting offered seats on the tube. Eventually that was the catalyst for me to find a Nutritional Therapist, and the rest is history.
What that period showed me, beyond the obvious lesson about taking unpersonalised advice from the internet, is that I was using fibre in extremes. Either avoiding it entirely, or eating so much of it that my gut simply couldn't cope.
Trend Cycles
Much like fashion, food and nutrition work in cycles.
After the height of veganism came the protein era. I think we might be past peak protein now, but you can still see the legacy of it everywhere, on the front of packaging calling out foods that have always naturally been high in protein, like yogurt or nuts, as if this is somehow new information. And then there are the ultra-processed snacks with isolated protein powder added into the factory mix.
The pushback against peak protein, possibly driven by a nation of constipated girlies who'd been living off protein shakes and cottage cheese, is fibre. And the same extreme is already happening. You can see it on TikTok but it's also trickling into packaged foods, drinks brands adding in fibre powders like inulin to products where fibre was never naturally present in the first place.
The question is how to stay grounded when the trends keep shifting. Much like I am never going back to low-rise jeans, I think the answer is to build a solid enough foundation, regardless of what trends come and go. The more people I work with, the clearer it becomes that most people simply haven't been told what that foundation is. It is protein, good fat, and fibre, at every meal, consistently, whether fibre is trending or not.
One thing worth knowing if you're exploring high-fibre packaged foods: if you've ever had a terrible time after eating Jerusalem (F)artichokes, inulin is the reason why. It's a highly fermentable fibre that can be brutal on a sensitive gut. It's worth reading labels carefully, just because something is marketed as high fibre doesn't mean it's the right fibre for you right now.
What is Fibre?
Fibre is essential fuel for your gut bacteria, and when your gut bacteria are well fed, the effects ripple out across almost every system in your body, your digestion, your immune function, your mood, your energy. It's the part of plant food your body can't break down, and that's not a design flaw, that's the whole point. The gut microbiome is in constant communication with your brain via the vagus nerve, producing neurotransmitters and regulating inflammation. Fibre is one of the primary ways you feed and diversify that ecosystem.
So this isn't just a conversation about keeping things moving, though it does that too. It's about whether the trillions of microorganisms living in your gut have what they need to do their job.
Insoluble vs soluble fibre
Most fibre content stops at "eat more of it." But the type of fibre you eat matters just as much as the amount.
Insoluble fibre is the old fashioned roughage, it doesn't dissolve in water, adds bulk to your stool and supports regular bowel movements. You'll find it in wholegrains, the skins of vegetables, brown rice, nuts and wheat bran. It's important, but if your gut is already inflamed or sensitive, introducing too much too quickly is like scrubbing an already irritated surface. This was my mistake with the raw salads and green smoothies, I thought I was doing something healthy, and I was making things much worse for myself.
Soluble fibre on the other hand dissolves and forms a gel in your digestive tract. It slows digestion, feeds your beneficial bacteria, and is generally much gentler on a reactive gut. The best example of this is a chia seed pudding, the grey, frog-spawn-like gel it forms when you soak them. Other examples are porridge oats, lentils, apples with the skin on, berries, and chickpeas. If you're starting from a place of gut sensitivity or discomfort, this is where you begin.
Your gut needs both types. But the order and pace at which you introduce them matters hugely, especially if your microbiome is already struggling.
Why fibre can cause bloating
A common concern is how to increase fibre without bloating. Someone decides to eat more fibre, adds the lentils, raw veggies and grains, feels awful within a few days, and concludes that fibre doesn't agree with them.
Here's what's actually happening. Your gut bacteria ferment fibre as part of their digestive process, and gas is a byproduct of that fermentation. Bloating when you increase fibre isn't a sign that something is fundamentally wrong, it's usually a sign that your gut microbiome isn't yet adapted to the amount or type you've introduced.
The most common reasons it happens: you've increased too quickly, you've introduced highly fermentable fibres before your gut is ready for them, or your microbiome is already compromised and more reactive than it should be.
The reassuring thing is that this is usually temporary. The microbiome adapts when you give it the right conditions and enough time. But it adapts much better when you go gradually.
Resistant starch
Resistant starch will have you thinking about leftovers differently. It is a third category of fibre that resists digestion in the small intestine and arrives in the colon intact, where it becomes food directly for your gut bacteria. When they ferment it, they produce butyrate, a short-chain fatty acid that feeds the cells lining your colon wall and plays a significant role in gut health and reducing inflammation.
What makes resistant starch particularly interesting is that cooking and then cooling certain starchy foods actually increases their resistant starch content. The cooling process changes the molecular structure of the starch. So cooled rice, potatoes, and pasta have a meaningfully different effect on your gut than the same foods eaten straight from the pan.
This is another win for batch cooking, and a good reason not to feel guilty about leftovers.
A note on leftovers: while there are benefits both nutritionally and practically for batch cooking, if you are someone who struggles with histamine, ie lots of allergies and take a lot of antihistamine tablets, it's important to note that the longer food has been left, for example leftovers, fermented foods, cured meats, the higher the histamine content.
What to do with this information today
A few simple places to start, without overhauling everything at once:
Start with one new fibre source this week
If your gut is sensitive, begin with soluble fibre, oats, soaked chia seeds, cooked apple, before adding large amounts of raw vegetables or wholegrains
Spread your fibre intake across the day rather than loading it all into one meal
Try cooking and cooling your rice or potatoes and adding it to your lunch
The longer term goal, once your gut has had time to adjust, is variety. Research consistently shows that eating a wide range of different plant foods across the week is one of the most significant things you can do for your microbiome. But variety built on a stable foundation is very different from throwing everything at it at once. Get the basics right first, then slowly build in more.
What I wish I'd had when I was first diagnosed was someone explaining the mechanisms of how food interacted with my body. Why fibre behaves differently depending on the type, why your microbiome needs time to adapt, why what works really well for your friend, colleague or sister might be completely wrong for you in this moment.
Your gut is very good at finding its way back to balance when you give it the right conditions. Most people just don't know what the right conditions are for them personally.
I hope this is a useful starting point. If you have questions you are always welcome to send me an email or DM. And if you're navigating a Crohn's disease diagnosis and trying to figure out where diet fits in, I hope this helps.