Fiber
Fiber is the part of plant food the small intestine cannot digest. It feeds gut bacteria, keeps bowel movements regular and slows how fast sugar reaches the blood. Adults need 25 to 38 g a day, depending on age and sex.
25-38 ga day for adults, adequate intake (US)
25 g or more a day for adults (EFSA, WHO)
Upper limit · none set; raise intake slowly
- Most per 100 g 35g White sorghum bran
- Most per portion 15g 1 cup black beans
- Main sources Beans and lentils then whole grains, seeds and fruit
- In animal foods 0 g meat, fish, eggs and dairy have none
Daily amount: the US adequate intake for adults aged 19 to 50, 21 to 30 g after 50 (National Academies). Food figures per 100 g from USDA FoodData Central; per portion, only for foods with a Caltide calorie page.
Foods High in Fiber
Ranked per 100 g, with what a usual portion gives, limited to 3 foods per category. Foods with a Caltide calorie page link to it.
W
White sorghum bran
35g / 100 g
C
Chia seeds
4.1 g in 1 tablespoon
Nutrition facts
34.4g / 100 g
S
Small white beans
24.9g / 100 g
C
Cranberry beans
24.7g / 100 g
F
Flax seeds (ground)
23.1g / 100 g
G
Great Northern beans
20.2g / 100 g
B
Barley
31 g in 1 cup
15.6g / 100 g
S
Sun-dried tomatoes
6.8 g in 1 cup
12.3g / 100 g
S
Steel cut oats
11.9g / 100 g
B
Bulgur
11.7g / 100 g
S
Sesame seeds
15 g in 1 cup
11.6g / 100 g
S
Sunflower seeds
16 g in 1 cup
11.1g / 100 g
Per 100 g vs. a Usual Portion
Why the food that ranks first per 100 g can give less in a real serving.
| Food | Usual portion | Per 100 g | Per portion |
|---|---|---|---|
| Chia seeds | 1 tablespoon (12 g) | 34.4g | 4.1g |
| Lentils | 1 cup (180 g) | 7.9g | 14g |
| Black beans | 1 cup (180 g) | 8.6g | 15g |
| Oats | 1 bowl, dry (40 g) | 10.1g | 4g |
| Pear | 1 medium (180 g) | 3.1g | 5.6g |
| Popcorn | 3 cups, popped (33 g) | 10.6g | 3.5g |
Chia seeds have far more fiber per 100 g than cooked lentils, yet one cup of cooked lentils gives more than three tablespoons of chia.
What Is Fiber?
Dietary fiber is a group of carbohydrates, plus a woody compound called lignin, that human digestive enzymes cannot break down. It passes the small intestine intact, which is why it gives about 2 kcal per gram instead of the 4 of starch and sugar.
What Fiber Does in the Gut
In the stomach and small intestine, soluble fiber such as the beta-glucan in oats forms a gel. The gel slows how fast the stomach empties and how fast sugar is absorbed, and it binds bile acids, so the liver draws on cholesterol to make more. EFSA accepts that 3 g of oat beta-glucan a day lowers LDL cholesterol.
In the large intestine, bacteria ferment part of the fiber into short-chain fatty acids, which feed the cells lining the colon. The fiber that is not fermented, mainly insoluble fiber from bran and vegetable skins, holds water and adds bulk, which makes stool softer and easier to pass.
A 2019 review of studies done for the WHO found that people eating 25 to 29 g of fiber a day had lower rates of heart disease, stroke, type 2 diabetes and bowel cancer than people eating less. These are observational links, backed by trials on risk factors such as cholesterol and body weight.
Why Most Days Fall Short on Fiber
A common day from our library, in usual portions, with bread, fruit and vegetables in it.
| Meal | Food | Amount | Fiber |
|---|---|---|---|
| Breakfast | Oats | 40g | 4g |
| Breakfast | Banana | 120g | 2g |
| Lunch | Bread | 50g | 1.1g |
| Lunch | Hummus | 34g | 1.8g |
| Lunch | Carrots | 61g | 1.9g |
| Snack | Orange juice | 250g | 0.78g |
| Dinner | Rice | 160g | 0.64g |
| Dinner | Chicken breast | 120g | 0g |
| Dinner | Broccoli | 90g | 2.2g |
| Total | 14g |
Two swaps fix most of it. A whole orange instead of the glass of juice adds about 2.6 g. A cup of cooked lentils instead of the white rice adds about 13.6 g. Together they lift this day past 25 g without adding a single meal.
Who Is Most Likely to Be Low in Fiber
Almost everyone. The Dietary Guidelines for Americans report that more than 90% of women and 97% of men eat less fiber than recommended, and EFSA found average adult intakes below 25 g in many European countries. The usual reason is too few beans, whole grains, fruit and vegetables, with refined grains and juice in their place.
Common Fiber Mistakes
Counting juice as fruit. A glass of orange juice has under 1 g of fiber; one whole orange has about 3.4 g.
Going from 10 g to 35 g in a week. Gut bacteria need time to adjust. A fast jump brings gas and bloating; add a few grams a week and drink more water.
Looking for fiber in protein foods. Meat, fish, eggs and dairy have none. Beans and lentils are the foods that give both.
How Much Fiber Do You Need?
The US sets fiber at 14 g for every 1,000 kcal: 25 to 38 g a day for adults aged 19 to 50, and 21 to 30 g after 50, because calorie needs fall with age.
| Age | Male | Female |
|---|---|---|
| 1 - 3 years | 19g | 19g |
| 4 - 8 years | 25g | 25g |
| 9 - 13 years | 31g | 26g |
| 14 - 18 years | 38g | 26g |
| 19 - 50 years | 38g | 25g |
| 51+ years | 30g | 21g |
| Pregnancy | - | 28g |
Fiber Supplements
Fiber supplements count toward the day, but each kind acts differently in the gut.
| Supplement | Kind of fiber | What to know |
|---|---|---|
| Psyllium husk | Soluble, gel-forming | One of the best studied; lowers LDL cholesterol and softens stool |
| Methylcellulose | Soluble, not fermented | Used for constipation; gut bacteria do not ferment it, so it tends to cause less gas |
| Wheat dextrin | Soluble, dissolves clear | Mixes into drinks without thickening |
| Inulin (chicory root) | Soluble, highly fermented | Feeds gut bacteria; the fermentation causes more gas than other fibers |
How to Take a Fiber Supplement
Take each dose with a full glass of water, start with a small dose, and raise it over a week or two.
Medicines That Interact With Fiber
- Most tablets and capsulespsyllium and other bulk fibers can slow or reduce their absorption; take medicines a couple of hours apart
Ask a doctor or pharmacist before combining a supplement with a medicine.
Tracking Fiber in Caltide
- Logged automaticallyCaltide adds up the fiber in every food you log and shows it against a daily fiber goal in the Nutrition tab. You can set your own goal.
- Supplements count tooAdd your fiber supplement once with its grams of fiber per dose. Each day you tick it off, it counts toward your total.
Fiber Sources and References
The figures and claims on this page are checked against these sources. Food amounts come from USDA FoodData Central.
- National Academies: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005)
- EFSA: Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre (2010)
- WHO: Carbohydrate intake for adults and children, WHO guideline (2023)
- Reynolds et al. (2019): Carbohydrate quality and human health, a series of systematic reviews and meta-analyses, The Lancet
- USDA FoodData Central
Questions About Fiber
Adults aged 19 to 50 need 25 to 38 g a day: the US adequate intake is 38 g for men and 25 g for women, and 30 g and 21 g after 50. EFSA and the WHO advise at least 25 g a day for adults.
In our food library, white sorghum bran: 35 g per 100 g. Chia seeds (34.4 g) and Small white beans (24.9 g) come next. Per usual portion, a cup of cooked beans or lentils gives the most.
Very little. Orange juice has 0.31 g per 100 g against 2.2 g in a whole orange, so a glass of juice gives a fraction of the fiber of the fruit.
Soluble fiber dissolves in water into a gel, slows digestion and can lower LDL cholesterol; oats, beans and psyllium are rich in it. Insoluble fiber does not dissolve and adds bulk to stool; wheat bran, whole grains and vegetable skins are rich in it.
No upper limit is set. A sudden large increase can cause gas, bloating and cramps, so raise intake over a few weeks and drink enough water.
They add fiber, but not the vitamins, minerals and other compounds that come with whole grains, beans, fruit and vegetables. Psyllium is one of the best studied; it can lower LDL cholesterol and help with constipation.
Some: about 2 kcal per gram, because gut bacteria ferment part of it into fatty acids the body absorbs. EU labels use 2 kcal per gram.
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