Fibre, plainly

If we could change one thing in the average British kitchen, it would be this one. Not the oil, not the supplements, not the sugar. Fibre — which nobody is excited about, and which does more measurable good than anything else we routinely suggest.

The number

In 2015 the Scientific Advisory Committee on Nutrition reviewed the evidence and raised the UK recommendation for adults to 30g of fibre a day. Most UK adults eat around 20g, and plenty eat considerably less.^1,2

For children the targets are lower and scale with age — roughly 15g at ages 2–5, 20g at 5–11, and 25g at 11–16.¹

That 10g gap in adults is the thing to fix. And it is genuinely closable without a new way of cooking, because 10g is about one tin of beans.

What it actually does

Fibre is the part of plant food we can't digest ourselves, which is exactly why it is useful. Some of it adds bulk and holds water, which is the bit everyone knows about. Some of it is fermented by the bacteria in the large intestine, which produce short-chain fatty acids that feed the cells of the gut lining. And some of it binds to things — bile acids, some cholesterol — and takes them out with it.

The SACN review found higher fibre intakes associated with lower rates of cardiovascular disease, type 2 diabetes and colorectal cancer.¹ That is a fairly remarkable return on a nutrient most people think of as being about regularity.

Fibre is the only thing on our list that is cheap, uncontroversial, available in every supermarket, and supported by consistent evidence across three major disease groups. We would be negligent not to lead with it.

Where it is

Roughly in descending order of how much you get per realistic portion:

• Beans, lentils and chickpeas — far and away the best source. A tin of baked beans or a jar of butter beans is around 10g.
• Wholegrains — wholemeal bread, oats, brown rice, wholewheat pasta, bulgur, barley.
• Nuts and seeds — a small handful of almonds is about 3g.
• Vegetables, skins on — peas, broccoli, carrots, sweetcorn, and potatoes with the skin left on.
• Fruit, especially with skin or seeds — pears, raspberries, apples, and dried fruit.

Note what is not on that list: fibre supplements. They have their place on medical advice, but they do one narrow job, whereas the foods above bring protein, minerals and a much wider range of fibre types with them.

Closing the gap without changing your life

None of that is a diet. It is the same shopping list with five different items on it, which is why it is still in place a year later when a regime would not be.

Variety, and the thirty-plants idea

You may have come across the suggestion of eating thirty different plants a week. It comes out of research into gut microbial diversity rather than from official guidance, and it is not a target the NHS sets — so treat it as a useful prompt rather than a rule you are failing.

What we like about it is that it changes the question from “how much” to “how many different”, which is the more useful question in most kitchens. Herbs, spices, tinned tomatoes, frozen peas, the seeds on the loaf and the different beans in a mixed tin all count. Households are usually surprised by how high they already are, and pleased by how cheap it is to add five more.

The mistake almost everyone makes

Going from 18g to 32g overnight. You will be bloated and uncomfortable for a week or two, decide fibre disagrees with you, and stop.

The gut bacteria that ferment fibre adapt to what you feed them, and that adaptation takes a few weeks. So add one thing, hold it for a fortnight, then add the next. And drink more water than you were — fibre holds water, and without enough of it the whole exercise works against you.

If you have a diagnosed gut condition — IBS, IBD, diverticular disease — the picture is more individual, and some high-fibre foods are genuinely less well tolerated. That is a conversation to have with your GP or with a practitioner who can look at your own pattern rather than the population average.

What we'd do this week

Buy two extra tins of beans or a couple of jars, and put them in whatever you were cooking anyway. Then change the bread. That is most of the gap, closed by Thursday, for about four pounds.