Key takeaways
- FDA defines label fibre as non-digestible carbohydrates and lignin intrinsic and intact in plants, plus isolated or synthetic ones FDA has determined have beneficial physiological effects.
- Soluble fibre attracts water and forms a gel that slows digestion; insoluble fibre adds bulk and helps food move through the gut.
- The Daily Value for fibre on US labels is 28 g; MedlinePlus puts the recommendation for older children and adults at 21 to 38 g a day, against an average intake of about 16 g.
- Fibre is a carbohydrate but provides about half the calories of other carbohydrates on average, which is part of why low-carb trackers subtract it.
- Add fibre gradually over a few weeks and drink fluids, because a sudden increase can cause gas, bloating and cramps.
Fibre sits inside the carbohydrate line of every US food label, yet it behaves differently from sugar and starch. For anyone counting carbohydrates, it is also the number that turns total carbs into net carbs. This guide explains what fibre is, what the label counts as fibre, and how to use the number, drawing on the FDA's guidance and the US National Library of Medicine's MedlinePlus.
What counts as fibre on a label
Since the Nutrition Facts label rule announced in May 2016, the FDA has defined dietary fibre that can be declared on a label as:
- non-digestible soluble and insoluble carbohydrates with three or more monomeric units, and lignin, that are intrinsic and intact in plants; and
- isolated or synthetic non-digestible carbohydrates that the FDA has determined have physiological effects beneficial to human health.
The FDA gives examples of those benefits: lowering blood glucose and blood cholesterol, reducing calorie intake and increasing the frequency of bowel movements. Natural fibre in vegetables, whole grains, fruit and bran needs no proof. Added fibres do. The 2016 rule identified seven isolated or synthetic fibres that qualify:
| Qualifying added fibres (2016 rule) |
|---|
| Beta-glucan soluble fibre |
| Psyllium husk |
| Cellulose |
| Guar gum |
| Pectin |
| Locust bean gum |
| Hydroxypropylmethylcellulose |
The FDA has since said it intends to propose adding more, including mixed plant cell wall fibres, inulin and inulin-type fructans, high-amylose (resistant) starch, galactooligosaccharide, resistant maltodextrin or dextrin, glucomannan and acacia gum, and allows them to be counted in the meantime.
Soluble and insoluble
MedlinePlus describes two kinds:
| Soluble fibre | Insoluble fibre | |
|---|---|---|
| What it does | Attracts water and turns to gel during digestion, slowing it | Adds bulk to the stool and helps food pass more quickly through the stomach and intestines |
| Found in | Oat bran, barley, nuts, seeds, beans, lentils, peas, some fruits and vegetables, psyllium | Wheat bran, vegetables and whole grains |
MedlinePlus adds that research shows soluble fibre helps lower cholesterol, which may help prevent heart disease, and that fibre in general aids digestion and helps prevent constipation. It also notes that most high-fibre foods contain both kinds, in proportions that vary by food. Under the federal labelling rule (21 CFR 101.9), the label must give one Dietary Fiber figure; separate soluble and insoluble lines are voluntary, unless the label makes a claim about that type of fibre.
How much, and how much people eat
The Daily Value for fibre on US labels is 28 g, the reference figure behind the %DV column. MedlinePlus gives a recommendation of 21 to 38 g a day for older children, adolescents and adults, and notes that Americans eat about 16 g on average. MedlinePlus adds that younger children will not be able to eat enough calories to reach that range. Treat these figures as reference points rather than a personal target, and ask a health professional about your own needs.
Why low-carb trackers subtract fibre
Fibre is a carbohydrate, so it is counted in Total Carbohydrate. But, as MedlinePlus explains, because of the way fibre is digested in the intestines it does not provide the same energy: carbohydrates provide 4 calories per gram, and fibre about half that on average. Low-carb trackers therefore subtract it to give net carbs. Net carbs explained covers the method and its limits, and sugar alcohols explained covers the other common subtraction.
A worked example. USDA FoodData Central's SR Legacy entry "Bread, whole-wheat, commercially prepared" gives 42.7 g of carbohydrate and 6.0 g of fibre per 100 g, and lists one slice as 32 g. That slice therefore has about 13.7 g of carbohydrate and 1.9 g of fibre: about 11.8 g net (11.75 g before rounding). Its fibre is 1.9 ÷ 28 ≈ 7% of the Daily Value. Now picture a hypothetical "high-fibre" wrap labelled 20 g of carbohydrate and 12 g of fibre: 8 g net. Before relying on that, check the ingredient list for added fibres such as inulin or resistant starch, and note that how they behave in your body may differ from intact plant fibre.
Adding fibre without discomfort
MedlinePlus warns that eating a large amount of fibre in a short time can cause gas, bloating and abdominal cramps, which often settle as the gut's bacteria adjust. Its advice is to add fibre gradually over a few weeks and to drink plenty of fluids, because water helps fibre pass through the digestive system.
Finding fibre in low-carb foods
If you are limiting carbohydrate, it helps to compare fibre and carbohydrate for the same weight of food. Low-carb vegetables and low-carb fruits list fibre alongside carbohydrate from USDA data. Ketora: Keto Diet Carb Tracker, one of our health and nutrition apps, subtracts fibre and sugar alcohols as you log and shows net and total carbs side by side.
Good to know
Frequently asked questions
What is dietary fiber?
What is the difference between soluble and insoluble fiber?
How much fiber should I eat a day?
Does fiber have calories?
Sources
- Questions and Answers on Dietary Fiber (opens in a new tab)US Food and Drug Administration — accessed
- Soluble vs. insoluble fiber (opens in a new tab)MedlinePlus, US National Library of Medicine — accessed
- Fiber (opens in a new tab)MedlinePlus, US National Library of Medicine — accessed
- Daily Value on the Nutrition and Supplement Facts Labels (opens in a new tab)US Food and Drug Administration — accessed
- 21 CFR 101.9 Nutrition labeling of food (opens in a new tab)Electronic Code of Federal Regulations (eCFR) — accessed
- FoodData Central: SR Legacy (April 2018 release) (opens in a new tab)US Department of Agriculture, Agricultural Research Service — accessed
About the author
Reign Creative LLC — The independent app studio that builds the apps covered on this site and publishes every article here. On Google Play it publishes as Reign Collective Apps.
We use AI tools to help research, draft and edit our articles. Each article lists the sources its factual claims rely on, and details about our apps come from their live Google Play listings. No article on this site has been reviewed by an independent expert unless the reviewer is named on it.
No person at Reign Creative LLC has read this article in full. It was published after automated checks and an AI editorial review, which are described in our editorial policy and are not the same as a person reading every sentence.
Spotted an error? Tell us — how corrections are handled is set out in our editorial policy.