Why more fibre made your bloating worse, and what to do

Because the bacteria in your large bowel ferment fibre, and fermenting makes gas. Add a lot of fibre at once and they have far more to work on than your gut is used to, which tends to mean bloating and wind. Go back to an amount you were comfortable with, then build up slowly.

That is not a sign fibre is wrong for you. It is usually a sign of pace. Below is what is going on, the foods most likely to do it, and the point where it stops being a pace problem and becomes a GP appointment.

Why does fibre make you bloated?

Fibre is the part of a plant you do not digest yourself. It passes through the small intestine largely untouched and arrives in the large bowel, where the bacteria living there ferment it.

Fermenting is good work. It produces short chain fatty acids that feed the cells lining your bowel. It also produces gas, and that is the part you feel. Soluble fibre in particular can produce gas, and in some people that means discomfort and bloating.

So when you go from a white toast breakfast to porridge, beans at lunch and a pile of roast veg at dinner, you have handed those bacteria a feast in one day. The gas arrives in proportion. Your gut has not had time to adjust, which is why UK fibre advice, from the British Dietetic Association to Guts UK, is to increase it slowly.

Which high fibre foods cause the most wind?

The irony is that the foods on the NHS list of things that make you fart are the same foods every “eat more plants” article tells you to add. The list covers cabbage, broccoli, cauliflower and brussels sprouts, pulses such as beans and lentils, dried fruit such as raisins and apricots, and onions. Sorbitol, the sweetener in some sugar free sweets and gum, is on it too, along with fizzy drinks and beer.

None of that makes those foods bad, only that a week which adds all of them at once is the week most likely to go wrong.

If you have IBS, the effect can be stronger. Fermentable fibre in larger amounts can cause bloating, gas and diarrhoea, because people with IBS may be more sensitive to some fibre types.

Does it settle down if I keep going?

Going slowly exists to give your gut time to adjust, so the hope is that it eases as you go. What I cannot give you is a number of days, because nobody has published one I would trust and guts differ.

What I would not do is grit your teeth and push through pain. Adding fibre slowly is meant to be comfortable. If it is not, you are going too fast, or fibre is not the whole story.

What should I do instead?

Step back to the last week you felt comfortable, then add one new higher fibre food at a time and give it a few days before the next. That way, if something sets you off, you know which one it was.

Here are some common jumps, and a gentler first step for each.

Drink more as the fibre goes up. Fibre needs fluid to move through the gut and do its job, and without it constipation is more likely. Smaller, more frequent meals help too, and they are on the NHS list of things to try for bloating.

Write it down while you do it. A note of what was new each day and how your stomach felt a few hours later turns a vague “fibre bloats me” into something you can read back. The Seven Day Bloating Log at the end of this page is built for that.

Is it the fibre, or something else?

If the bloating was there before you changed anything, the fibre may only be making an existing pattern louder. I had bloating for years on the wards and thought that was who I was. It is worth separating the two before you blame the porridge.

The NHS puts most bloating down to gas, but that gas can come from swallowed air, constipation, a food intolerance, coeliac disease or IBS as well as from what you eat. Why am I bloated all the time goes through how to tell them apart, and the bloating quiz points you at where to start in about a minute. If your symptoms lean towards constipation or towards loose stools, soluble versus insoluble fibre explains why the type of fibre can matter as much as the amount.

When should I stop and see a GP?

When changing what you eat has not helped. The NHS says to see a GP if “you feel bloated regularly” or “you’ve tried changing your diet but keep feeling bloated”, and also if “you have bloating and unintentional weight loss” or “you have bloating and also have blood in your poo”.

Ask for an urgent GP appointment or call 111 if “you have bloating with vomiting (being sick), diarrhoea or constipation”, if “you have a swelling or lump in your tummy”, or if “you cannot pee, poo or fart”.

Call 999 or go to A&E if you have bloating with a swollen stomach and “you have a stomach ache that is severe and came on very suddenly”, or “you’re vomiting blood or your vomit looks like ground coffee”.

If you have a diagnosed gut condition, talk to your GP or dietitian before you change how much fibre you eat.