High fibre vs source of fibre, the numbers on a UK label

In Great Britain, a food labelled high fibre must contain at least 6g of fibre per 100g, or at least 3g per 100 kcal. Source of fibre needs at least 3g per 100g, or 1.5g per 100 kcal. Below 3g per 100g, and without the calorie route, a pack can’t make either claim, however wholesome it looks.

Those two numbers are the most useful thing on a bread wrapper or a cereal box, and they are printed on the back, in small type, next to nothing exciting.

What are the legal thresholds for fibre claims?

The conditions sit in the list of permitted nutrition claims in Regulation 1924/2006, which still applies in Great Britain. Each condition also covers “any claim likely to have the same meaning for the consumer”, so packed with fibre or full of fibre has to clear the same bar as the official wording.

None of those conditions looks at sugar, salt or fat. A high fibre cereal can be high in sugar too, and the claim is still lawful.

Why is there a per 100 kcal route, and when does it matter?

It lets low calorie foods qualify. Vegetables, soups and some ready meals carry a lot of water, which drags the per 100g figure down even when the fibre in a bowl is respectable.

It also means a fibre claim on a light food can rest on less fibre by weight than you’d guess. Take a soup with 40 kcal and 1.2g of fibre per 100g. That works out at 3g of fibre per 100 kcal, which meets the high fibre condition, while the per 100g figure is well short of a source of fibre. Neither number is wrong. They answer different questions, and the label won’t tell you which route the claim used. Look at both columns and do the sum if the front says high fibre on something watery.

How much fibre is that in a slice or a bowl?

Less than the word high suggests. Per 100g is a fair way to compare two products, and an awkward way to count your day.

Say a loaf has 6g of fibre per 100g and a slice weighs 40g. Two slices give you 4.8g. Adults are advised to aim for 30g a day, and the NHS puts most adults at an average of about 20g, so a high fibre sandwich covers a useful slice of the gap without closing it. Children need less: about 15g a day from 2 to 5, 20g from 5 to 11 and 25g from 11 to 16.

Check the slice or portion weight on the pack before you do the arithmetic, because loaves vary. The point is the habit, not my example.

Does added fibre count?

Yes, if it meets the legal definition. Fibre on a UK label means carbohydrate polymers with three or more units that are neither digested nor absorbed in the small intestine. That covers fibre naturally present in the food, fibre extracted from food raw materials, and synthetic fibre, with the last two counting only where a beneficial physiological effect is shown by generally accepted scientific evidence.

So a white loaf with added fibre can reach high fibre, and added fibres such as inulin or chicory root fibre are one way to get there. Higher fibre white bread is a reasonable choice if white is what your household will eat. The type of fibre matters for some people, though. If you have IBS, fermentable fibre in larger amounts can cause bloating and gas, so a loaf that wins on the number won’t suit everyone. Increase fibre gradually, with plenty of fluid. If more fibre has already made things worse, this post on fibre and bloating is the one to read next.

Why is fibre missing from some labels?

Because it is optional. The mandatory nutrition declaration in the UK covers energy, fat, saturates, carbohydrate, sugars, protein and salt. Fibre is on the list of extras a manufacturer may add.

The rule flips once a claim is made. Under Article 7 of the claims regulation, when a nutrition or health claim is made for a nutrient such as fibre, the amount has to be declared. A pack that says source of fibre must show you the number that proves it.

The traffic light colours on the front never include fibre either. They cover fat, saturates, sugars and salt, so a high fibre food gets no green light for it. The traffic light label explained covers what those colours do and don’t measure.

Can a fibre claim say anything about your gut?

Only in approved words, and each set of words comes with its own condition. The government’s claims register authorises a handful of fibre health claims, including:

• Oat grain fibre and barley grain fibre contribute to an increase in faecal bulk.
• Rye fibre contributes to normal bowel function.
• Wheat bran fibre contributes to an acceleration of intestinal transit, and the pack must say the effect comes from at least 10g of wheat bran fibre a day.

Each of those three may only be used on a food that is high in that fibre. Chicory inulin has its own authorised claim about normal bowel function, which depends on a daily intake of 12g. Anything looser, such as good for digestion, is not on the list in that form.

How do you use the numbers in the shop?

Find fibre per 100g on the back, and hold it against 3 and 6. Between two loaves or two cereals, that one figure usually settles it, with sugars per 100g as the tiebreak. For bread in particular, how to choose a high fibre bread goes aisle by aisle.

If you’d like to test yourself on claims like these before your next shop, the label test has six of them, true or false.