Fibre, cheaply: what a week of Portland shopping buys
Most adults get about half the fibre they need. Closing the gap is one of the cheapest changes in nutrition — here is what a week of it actually looks like on a receipt.
The gap most people have
The usual recommendation is around 30g of fibre a day for adults. Most people in the US get somewhere near half that, and the gap has more to do with what is convenient than with what is expensive.
That is the unusual thing about fibre among nutrition problems: the fix is cheaper than the problem. Almost everything high in fibre is among the least expensive food in the shop.
Where it actually comes from
Beans, lentils and chickpeas carry more fibre per dollar than anything else you can buy. A tin of black beans is somewhere around 12g. Dried, the same money buys three or four times as much.
After that: whole oats, wholemeal bread rather than white, brown rice or barley, potatoes with the skin left on, frozen peas, frozen berries, apples, pears, carrots, and any nut or seed you like enough to actually eat.
Frozen counts. Tinned counts. The fibre does not care.
What a week looks like
Oats in the morning, which is about 4g. A tin of beans folded into something at two evening meals, which is 12g each time. Wholemeal instead of white across the week, which is another 8g or so. Fruit twice a day, potatoes with skins, peas with dinner.
None of that is a diet and none of it requires shopping anywhere in particular. It is roughly a dozen items and it lands most people close to the target without anything being weighed.
Go slowly, and drink more water
The one piece of advice worth taking seriously: increase it over two or three weeks rather than in a day. Going from 12g to 30g overnight is uncomfortable in an entirely predictable way, and it is the reason most people who try this stop.
Fibre also draws water into the gut, so more of it without more fluid tends to make things worse rather than better.
Where this does not apply
Some conditions need the opposite advice, at least for a while — active flares of inflammatory bowel disease, certain strictures, and the run-up to some procedures. If you have been told to limit fibre by a clinician who knows your history, that advice beats this article.
If you are not sure which applies to you, that is a good five-minute conversation at your next appointment rather than a decision to make from a page.
Medically reviewed by Dr. Sarah Lindqvist
MD · Primary care, Pearl District · Reviewed Jun 25, 2026
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