The Fibre Gap: The Nutrient Almost Everyone Is Short On

If protein is over-marketed, fibre is the opposite: a nutrient with genuinely impressive evidence behind it and almost no advertising budget. Large reviews of the research consistently link higher fibre intake with lower rates of heart disease, type 2 diabetes, bowel cancer and death from any cause.

And almost nobody eats enough of it. Estimates across the US and UK put the proportion of adults meeting the target at somewhere around one in ten.

The target

Roughly 30 g a day for adults (US guidance is often expressed as 25 g for women and 38 g for men; the UK uses 30 g). Average intake is nearer 15–20 g. So most people need to roughly double it.

The two kinds, and why you need both

• Soluble fibre dissolves into a gel: oats, beans, apples, psyllium, barley. It slows glucose absorption and binds cholesterol.
• Insoluble fibre does not dissolve: wholegrains, nuts, the skins of vegetables. It adds bulk and keeps things moving.
• Resistant starch deserves its own mention. It's found in cooled potatoes and rice, green bananas and legumes, and it feeds gut bacteria particularly well.

Nobody needs to track which is which. Eat a wide range of plants and you get both by default.

Where the fibre actually is

• Cooked lentils, one cup — about 15 g. Nothing else comes close for the money.
• Black beans, one cup — about 15 g.
• Raspberries, one cup — about 8 g.
• Chia seeds, two tablespoons — about 10 g.
• One large pear with the skin on — about 6 g.
• Rolled oats, 50 g dry — about 5 g.
• One avocado — about 10 g.
• Wholegrain bread, one slice — about 2–3 g (and white bread, essentially none).

How to double it without hating your life

1. Add, don't replace. A tin of lentils thrown into a bolognese, a handful of frozen peas in the pasta water, chia in the yoghurt. You will barely notice, and you have added 10 g.
2. Leave the skins on. Potatoes, apples, cucumbers, aubergine. Peeling is a fibre-removal service.
3. Switch one carb. White rice to brown or barley. White bread to a proper seeded wholegrain — check that the first ingredient is a wholegrain, not "wheat flour" with caramel colouring.
4. Keep a legume of convenience. A tin of chickpeas in the cupboard is the fastest fibre in the world.

Go slowly, and drink water

If you jump from 15 g to 35 g overnight, you will be uncomfortable and you will blame fibre. Increase by about 5 g a week, and increase water alongside it — soluble fibre needs fluid to do its job, and without it, more fibre can actually make constipation worse.

One exception worth flagging: if you have IBS or another diagnosed gut condition, some high-fibre foods (particularly certain legumes and wheat) can trigger symptoms. That does not mean fibre is bad for you — it means the type matters, and it is worth working through with a dietitian rather than guessing.