Most of us eat well short of the 30g of fibre a day the NHS recommends. Here’s how to close the gap without bloating, cramps or a very windy office.
You’ve read the headlines. Fibre is good for your heart, your bowel and your blood sugar, and almost nobody gets enough. So on Monday you swap the white toast for bran flakes, put lentils in the bolognese and eat beans for lunch.
By Wednesday you’re bloated, crampy and keeping a careful distance from colleagues. Fibre is still a good idea. The mistake was trying to do a month’s work in three days.
The UK recommendation for adults is 30g a day. It was raised in 2015, when the evidence on fibre and long-term health prompted a rethink of the old, lower target. The British Heart Foundation and NHS dietitians both work to the 30g figure.
Most of us fall well short. NHS guidance in Scotland puts typical intake at about 20g a day, so the average British man needs to find another 10g or so. That gap is the problem. Try to close it in a weekend and your gut will let you know.
The good news is that 30g doesn’t call for a strange diet or expensive powders. It comes from ordinary food: oats, wholemeal bread, beans, lentils, vegetables, fruit, nuts and potatoes with the skins on.
Fibre is the part of plant food you can’t digest. It travels down to your large bowel, where trillions of bacteria get to work on it. That fermentation is behind many of fibre’s benefits. It also produces gas.
Your gut bacteria are used to whatever you normally eat. Give them a sudden glut of fibre and they produce more gas than your bowel is used to dealing with. Hence the bloating, rumbling and wind.
The gut does adapt. Mayo Clinic dietitians say one of the most common mistakes is doing too much too fast, and recommend building up fibre over weeks rather than days. Research summarised by UCLA Health found that people who added beans to their diet were generally back to normal levels of wind within three to four weeks. NHS advice says the same thing: increase fibre gradually so your gut has time to adjust.
The trick is to make one small change, live with it for several days, then add the next. If things get uncomfortable, stay at that level for a few more days before moving on. Here is a sensible order that suits most British kitchens.
Start with breakfast. Swap a sugary cereal for porridge oats, or a wholegrain cereal such as shredded wheat. Oats are rich in soluble fibre, which tends to be kinder to the gut, so they make a gentle first step. Top them with a sliced banana or a handful of berries.
Next, change your bread. Moving from white to wholemeal is the easiest swap in the book, because you’re eating the sandwich anyway. If wholemeal seems a step too far, try a half-and-half loaf for a week or two first.
Then bring in pulses, but in small amounts. Start with a couple of spoonfuls rather than the whole tin. Baked beans on wholemeal toast is a classic British high-fibre meal. A handful of red lentils disappears into a bolognese, chilli or soup, and kidney beans or chickpeas can stretch a curry. Once you’re comfortable with small portions, make them bigger.
Finally, fill the gaps. Leave the skins on potatoes, add an extra vegetable to dinner, keep fruit or a small handful of unsalted nuts for snacks, and try wholewheat pasta or brown rice now and then rather than every night.
When you’re shopping, check the label. In the UK, a food can only be called high in fibre if it has at least 6g per 100g. That makes it a quick way to compare cereals and breads.
Fibre is a long-term habit, not a challenge. Add a little more each week and your gut will keep up. Add it all at once and it won’t.
Yes, and people forget this step more often than any other. Fibre works by holding on to water, which keeps your stools soft and easy to pass. If you add fibre without drinking more, you can end up constipated, which is the opposite of what you wanted.
NHS hospital dietitians suggest 6 to 8 cups of fluid a day, or around 2 litres, spread through the day. Water, lower-fat milk and sugar-free drinks all count, and so do tea and coffee. Beer doesn’t count, however much you’d like it to.
Exercise helps as well. Regular walking helps keep things moving through the gut, and it’s good for almost everything else on your midlife list.
Some extra wind in the first few weeks is normal. Pain that keeps you awake, bloating that never settles, or a gut that gets worse rather than better as the weeks go by is worth paying attention to.
If you have irritable bowel syndrome (IBS), fibre needs a more careful approach. NHS inform says a sudden increase can make IBS symptoms worse. Some NHS guidance also notes that insoluble fibre, the rougher kind found in bran and skins, can make wind and bloating worse for some people with IBS. Soluble fibre from oats and fruit is often better tolerated. If you think you have IBS, talk to your GP. They can refer you to a dietitian if needed.
Don’t put everything down to your new diet, either. NHS 111 Wales lists the main symptoms of bowel cancer as persistent blood in your poo, a persistent change in bowel habit (usually going more often, with runnier stools) and pain in your tummy. Most people with these symptoms don’t have cancer. But if a change lasts for several weeks, or you see blood, book a GP appointment rather than blaming the lentils. If you get a bowel screening kit through the post, do the test.
Fibre supplements and powders are sold in every pharmacy, and they have their place. Most people, though, can reach 30g from food, which also brings vitamins, minerals and a full stomach that a powder can’t. If you’re thinking about a supplement, or you take regular medicines, ask your pharmacist first.
UK adults should aim for about 30g of fibre a day, and most men get closer to 20g. To close the gap without bloating, make one swap at a time over several weeks: porridge, then wholemeal bread, then small portions of beans and lentils, and drink plenty of fluid as you go. Some extra wind at first is normal and usually settles within a few weeks. If pain, bleeding or a change in bowel habit doesn’t go away, see your GP.
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