Fibre: the one nutrient almost everyone is short of, and the numbers behind it

Fibre is the rare case where the evidence is strong, consistent and boring. More of it means less heart disease, less diabetes, less colorectal cancer and fewer deaths, in cohorts covering a hundred million person-years and in trials that move blood pressure and cholesterol. Almost nobody eats enough.

How much you need

• The Daily Value for dietary fibre on a food label is 28 g a day. — adults and children 4 years and older Evidence E source
• The fibre recommendation is 14 grams per 1,000 kcal, which works out at 25 grams a day for women and 38 for men, and it was derived from population data on heart disease rather than from trials of fibre itself. — healthy adults in the United States Evidence E source
• The 28 g on the label is not a measurement of anybody's need: it is 14 g of fiber per 1,000 kcal multiplied by a 2,000 kcal reference day. — adults and children 4 years and older in the United States Evidence E source
• The number behind the label was chosen for the heart, not for the bowel: the IOM picked 14 g per 1,000 kcal as the intake that most reduced coronary heart disease risk. — United States general population Evidence E source
• WHO's 2023 target is at least 25 g a day and it is deliberately about fiber in food, not fiber in a tub: the wording is 'naturally occurring dietary fibre as consumed in foods'. — adults; separate conditional figures for children and adolescents Evidence E source
• More is not endlessly better: the intake band where the most health outcomes improved was 25-29 g a day, and WHO's target is the bottom of it. — adults Evidence E source
• USDA's practical rule for reading a label is 3 grams: that is what makes an item fiber-rich, and the cheapest way to hit it is the less processed form of a food you already eat. — United States general population Evidence E source
• 'Soluble' and 'insoluble' have no Daily Value behind them: FDA looked for a basis to set one and said there is none. — United States labelling Evidence E source

How well your body absorbs it

• The old worry that fiber steals your iron does not show up in the trials: across 32 studies, fiber intake had no consistent link with iron absorption or iron status. — 32 studies, of which 9 were clinical and 23 in vivo; fibers included fructo-oligosaccharides, galacto-oligosaccharides, inulin, pectin, guar gum, oligofructose, xylo- and mannan-oligosaccharides Evidence C source
• The same gram of fiber worked better inside food than inside a supplement, and this is the one conclusion the journal version of the review left out. — non-infants with normal bowel function; evidence most applicable to generally healthy adults Evidence A source

Who is most likely to fall short

• In residential care the fiber problem is not only the menu: residents were offered 21.4 g a day and actually ate 15.8 g. — residents aged over 65 in residential care facilities Evidence C source
• Children's fiber trials used very different doses depending on the fiber: 2.4 to 15 g a day of inulin-type fructans against 6 to 25 g of psyllium. — healthy children aged 1-18 at baseline, including some who were overweight or had mild hypercholesterolaemia Evidence C source
• Two of the things fiber is most often sold to children for have never been tested in children: postprandial blood sugar and colonic transit time. — healthy children aged 1-18 Evidence C source
• Fiber is one of the nutrients American children and teenagers most consistently fall short on, across twenty years of national surveys. — individuals aged 1-18 in NHANES 2001 to March 2020, pregnant girls excluded Evidence C source

What the evidence does and does not show

• Pooling 185 prospective studies covering almost 135 million person-years, the people eating the most fibre had 15 to 30 per cent less death and heart disease than those eating the least. — adults without chronic disease, 185 prospective studies and 58 trials Evidence C source
• The same review found the benefit was largest between 25 and 30 grams of fibre a day, and that trials confirmed lower weight, blood pressure and cholesterol. — adults in 58 clinical trials Evidence A source
• An umbrella review of 33 meta-analyses covering 17 million people rated the evidence convincing for three outcomes: cardiovascular death, pancreatic cancer and diverticular disease. — 17,155,277 individuals across 38 health outcomes Evidence C source
• In people with diabetes, raising fibre intake lowered HbA1c, fasting glucose, insulin resistance and cholesterol across dozens of trials. — adults with prediabetes, gestational, type 1 or type 2 diabetes, 42 trials Evidence A source
• In people who already have high blood pressure, more fibre lowered systolic pressure by about 4 mmHg, on high-certainty evidence. — adults with cardiovascular disease or hypertension, 12 trials Evidence A source
• For chronic constipation, fibre supplements worked in two thirds of people against four in ten on control, and flatulence went up with them. — adults with chronic constipation, 16 trials Evidence A source
• Fibre supplements increase how often and how easily people with chronic constipation go, but only above about 10 grams a day and only after four weeks or more. — adults with chronic constipation, 16 randomised trials of supplemental fibre against placebo or control Evidence A source
• The dose-response curve for type 2 diabetes is flat until about 20 grams of fibre a day and only then starts to fall, which is the clearest picture of where a daily target would sit. — adults in 17 prospective cohorts, followed for incident type 2 diabetes Evidence C source
• Coronary heart disease is the outcome the fibre recommendation was built on, and in pooled cohorts the highest fibre eaters had 7 per cent fewer coronary events and 17 per cent fewer coronary deaths than the lowest. — adults in 18 cohorts, followed for coronary heart disease incidence and mortality Evidence C source
• For stroke the same pattern holds in eleven cohorts, with about 17 per cent lower risk in the highest fibre group, but the link with dying of a stroke was not statistically significant. — adults in 11 prospective cohorts, followed for stroke incidence and stroke mortality Evidence C source
• Whole grains showed the same pattern as fibre in the same review, and the dose-response curves suggested even higher intakes could help further. — adults without chronic disease, 185 prospective studies and 58 trials Evidence C source
• Glycaemic index and glycaemic load, the other two ways of judging carbohydrate, held up far worse than fibre in the same analysis. — adults without chronic disease Evidence C source
• A gram of fiber is not a gram of fiber: cereal fiber added about 2.17 g to daily stool weight, vegetable fiber 2.03 g, and fruit fiber only 0.88 g. — healthy humans in 93 intervention publications, trials dating back to 1919; 26 different fiber types Evidence B source
• What decides how much a fiber bulks the stool is whether gut bacteria can eat it: non-fermentable fiber added 2.88 g per gram, fermentable fiber 0.89 g. — healthy humans in 93 intervention publications Evidence B source
• Even fibers of the same chemical family behave differently by plant: among galactomannans, fenugreek moved blood sugar and guar gum moved blood lipids. — healthy adults and patients with metabolic disorders in 50 randomised controlled trials: 27 guar gum, 20 fenugreek, 2 mixed galactomannan, 1 locust bean gum Evidence C source
• A year of soluble corn fiber built measurably more bone in girls aged 9-14, and did nothing measurable in boys. — healthy children and adolescents aged 9-14 with habitually low calcium intake; 69.5% Hispanic, 41.3% White Evidence B source
• Cooking a potato and then chilling it for days turns some of its starch into fiber-like resistant starch, and the blood-sugar response drops: insulin fell about a quarter in the first half hour. — 30 women, mean BMI 32.8, fasting glucose 110.5 mg/dL and insulin 10.3 uIU/L, i.e. already above normal Evidence B source
• How coarsely the grain is milled changes the meal: porridge from coarse oat flour gave a lower glucose and insulin rise than the same weight of finely milled oats. — 20 healthy adults, 10 male and 10 female, mean age 25.3 years, mean BMI 23.2 Evidence B source
• Whole grain wheat did not beat refined wheat on blood sugar once the two were matched for grain, form, particle size and thickness: the advantage people expect came from the processing, not from the bran. — 16 healthy participants Evidence B source
• Fiber really does soften stool, and the size of it is tiny: about 0.013 Bristol units per extra gram a day, which the reviewers themselves call likely unimportant to most people. — non-infants with normal bowel function, excluding people with conditions affecting gut motility; evidence base primarily generally healthy adults Evidence A source
• For people who are actually constipated the type matters: viscous soluble fiber beat placebo on straining with high certainty, while insoluble fiber's top ranking rested on very low certainty evidence. — adults with chronic idiopathic constipation Evidence A source
• If your transit time is already normal, eating more fiber does not speed it up: the gain shows only in people whose transit was already 48 hours or longer. — healthy humans in intervention trials of cereal, fruit and vegetable fibers Evidence B source
• Fiber added to a product to make it filling usually is not: across 136 trials most isolated fibers changed neither appetite ratings nor how much people ate. — healthy adults Evidence A source
• Viscosity, not fermentability, is what separated the fibers that dulled appetite from the ones that did nothing. — healthy adults Evidence A source
• The largest review of fiber and bowel function says plainly that not one of its 113 trials was actually built to answer the question it asked. — the trial literature on fiber and laxation in people with normal bowel function Evidence A source
• When fiber trials used real food rather than a powder, the trials often could not say how much fiber they had actually added. — 113 trials of fiber and laxation Evidence A source
• Whether more fiber actually stops healthy people from becoming constipated is, in the reviewers' word, unclear. — people entering trials with normal bowel function Evidence A source
• Across 33 meta-analyses and 17 million people, only three outcomes reached the top credibility class: cardiovascular death, pancreatic cancer and diverticular disease. — general adult populations worldwide Evidence C source
• The famous breadth of fiber's benefits is thinner than it looks: in the 2018 umbrella review, 3 of 21 outcomes had convincing evidence, and only 2 of those came from prospective studies. — general populations in prospective observational studies Evidence C source
• In intensive care, the standing worry that fiber in tube feed causes gut trouble was turned around: fiber-containing formulas came with 39% fewer gastrointestinal complications. — hospitalised adults with critical illness receiving enteral nutrition Evidence B source
• Psyllium is the best-studied fiber for constipation and still lost to cheaper things: the single highest-quality placebo trial found no benefit, and head-to-head it trailed polyethylene glycol, lactulose and fruit. — adults with chronic constipation Evidence A source
• Prebiotic fiber marketed for a sensitive gut did not settle one: across 11 trials it changed neither symptoms nor quality of life in irritable bowel syndrome, though it did shift the bacteria. — adults with irritable bowel syndrome and other functional bowel disorders Evidence A source
• The clinical caution against fiber in tube feeding was an opinion, not a finding: before this review nobody had assessed it comprehensively. — hospitalised adults with critical illness Evidence B source
• Three quarters of the meta-analyses ever pooled on fiber point the same way, and that consistency is itself the strongest thing anyone can honestly say about it. — general adult populations worldwide Evidence C source

What too much does

• More fibre also means more wind, and the trials measured it. — adults with chronic constipation, 16 trials Evidence A source
• WHO found no upper limit worth setting for food fiber, with one loose end it chose to name: a very-low-certainty signal of higher endometrial cancer risk at higher intakes. — adults Evidence E source
• One fiber can make the exact symptom worse that another fiber improves: inulin-type fructans increased flatulence severity while other prebiotics reduced it. — adults with irritable bowel syndrome and other functional bowel disorders Evidence A source
• Fiber supplements for constipation are unpleasant more often than they are dangerous: bloating and wind were the usual complaints, and they stayed mild to moderate. — adults with chronic constipation taking over-the-counter products Evidence A source
• There is no settled dose of psyllium: the trials behind the recommendation ran from 3.5 g a day to 22 g a day. — adults with chronic constipation Evidence A source

What to do with this

Raise it slowly and drink more water. Going from 15 grams to 30 in a week produces exactly the wind and bloating that makes people give up, and the trials that measured flatulence found it goes up with fibre. Two to three weeks of gradual change is the difference between a habit and a bad memory.

The cheapest route is beans and lentils. A cup of cooked lentils carries most of a day. After that: whole grains instead of refined, fruit with the skin, vegetables, nuts and seeds. The evidence points at food rather than at a supplement, because that is what the cohort studies measured.

A supplement does have one clear use. For chronic constipation, fibre supplements worked in two thirds of people against four in ten on control, with psyllium doing best, at doses above 10 grams a day and after at least four weeks.

If you want a number to aim at rather than a label, the cohort curves are the best guide there is. The risk of type 2 diabetes barely moves until about 20 grams a day and only then starts to fall, which makes 20 a floor rather than a goal, and the largest reductions sit between 25 and 30 grams.

If you have high blood pressure or diabetes, fibre is unusually worth your attention. In people with hypertension, more fibre lowered systolic pressure by 4.3 mmHg on high-certainty evidence, and in diabetes it lowered HbA1c and fasting glucose across dozens of trials.

If you are buying a fibre supplement for constipation, know what you are buying. Psyllium is the best-studied fibre there is, and in the single highest-quality placebo-controlled trial it did not beat placebo. Head to head, polyethylene glycol, lactulose, mango and prunes all outperformed it on stool frequency and consistency. The doses behind the recommendation run from 3.5 grams a day to 22, a sixfold spread, so a pooled statement that psyllium works hides which dose was tested.

For people who are actually constipated, the type seems to matter and the usual advice has it backwards. Viscous soluble fibres beat placebo on straining with high certainty and on stool consistency and frequency with moderate certainty. Insoluble fibre, the bran people reach for, ranked first on overall symptom score on very low certainty evidence from a thin network of 17 trials.

If your transit time is already normal, more fibre will not speed it up. The shortening showed up only in people whose transit was already 48 hours or longer, where it ran to roughly half an hour per gram a day.

One fibre can worsen the exact symptom another one settles. Inulin-type fructans made flatulence significantly worse, while other prebiotics at 6 grams a day or less improved it. If you are adding a named fibre and feeling worse, the fibre and not your gut may be the thing to change. Bloating and wind are the usual complaints with psyllium, inulin and polydextrose, and in the trials they stayed mild to moderate with no serious adverse events.

Where to get it from food

The bottom line

Twenty-eight grams a day is the label target, and the recommendation underneath it, 14 grams per 1,000 kcal, was derived from population data on heart disease rather than from trials of fibre. The cohorts behind it are consistent about direction: fewer coronary events, fewer coronary deaths, about 17 per cent less stroke among the highest fibre eaters, though the link with dying of a stroke did not reach significance. There is no upper limit, though going up fast brings wind and bloating, so raise it over weeks rather than days and drink more water while you do. The foods that carry it are the boring ones: beans, lentils, whole grains, nuts, fruit with the skin on, vegetables. A fibre supplement works for constipation above about 10 grams a day and after four weeks, and it is a poor substitute for the diet the cohort studies were actually describing. A large amount has landed under this page since it was written, and most of it makes the picture smaller rather than larger. The 28 grams is arithmetic: 14 grams per 1,000 kcal times a 2,000 kcal reference day, and the 14 was chosen for coronary heart disease rather than for your bowel. WHO's 2023 target of at least 25 grams is worded deliberately as fibre in food rather than fibre in a tub, and 25 is the bottom of the 25 to 29 gram band where the most outcomes improved. On bowels specifically, the honest summary is uncomfortable. Each extra gram a day softens stool by about 0.013 Bristol units, which the reviewers themselves call likely unimportant to most people, and whether more fibre stops healthy people becoming constipated is stated in that review as unclear. The same review found fibre eaten in food associated more strongly with those outcomes than fibre swallowed as a supplement. None of that touches the cohort evidence on heart disease, diabetes and colorectal cancer. That is where fibre's reputation was earned. Even there the strongest honest statement is consistency: 29 of 33 meta-analyses point the same way, while only three outcomes reach the top credibility class.

Sources

1. fib-01 · Position of an expert body · regulatory reference value
   28 g (value from the source's table, not a sentence)
   FDA, Daily Value on the Nutrition and Supplement Facts Labels (updated 2024-03-05) · checked 2026-09-15 · independently re-checked
2. fib-r5-1 · Position of an expert body · expert body position statement
   Dietary Reference Intakes recommend consumption of 14 g dietary fiber per 1,000 kcal, or 25 g for adult women and 38 g for adult men, based on epidemiologic studies showing protection against cardiovascular disease...The Dietary Reference Intakes for fiber are based on recommended energy intake, not clinical fiber studies. Usual intake of dietary fiber in the United States is only 15 g/day.
   Slavin, position of the American Dietetic Association, Journal of the American Dietetic Association, 2008 · checked 2026-09-17 · independently re-checked
3. fib-e1-09 · Position of an expert body · federal rulemaking
   Using a reference calorie intake of 2,000 calories (see section II.A.3.), we are proposing to amend Sec. 101.9(c)(9) to set a DRV of 28 g (14g/1,000 kcal x 2,000 kcal/d) for dietary fiber.
   FDA, Food Labeling: Revision of the Nutrition and Supplement Facts Labels (proposed rule), 79 FR 11879 · checked 2026-09-18 · independently re-checked
4. fib-e1-10 · Position of an expert body · federal rulemaking
   The AI was primarily based on the intake level that was associated with the greatest reduction in the risk of CHD.
   FDA, Food Labeling: Revision of the Nutrition and Supplement Facts Labels (proposed rule), 79 FR 11879 · checked 2026-09-18 · independently re-checked
5. fib-e1-11 · Position of an expert body · guideline recommendation
   In adults, WHO recommends an intake of at least 25 g per day of naturally occurring dietary fibre as consumed in foods (strong recommendation).
   WHO, Carbohydrate intake for adults and children: WHO guideline, 2023 · checked 2026-09-18 · independently re-checked
6. fib-e1-12 · Position of an expert body · guideline recommendation
   In studies comparing individuals with the lowest fibre intakes with those consuming discrete ranges of increasing intake, the range that demonstrated greatest benefit for the largest number of health outcomes was 25–29 g per day.
   WHO, Carbohydrate intake for adults and children: WHO guideline, 2023 · checked 2026-09-18 · independently re-checked
7. fib-e1-13 · Position of an expert body · government dietary data brief
   The dietary fiber density of the diet can be increased by including fruits, vegetables and whole grains that are fiber-rich (3 grams or more fiber per labeled serving (3)).
   FSRG Dietary Data Briefs, USDA Agricultural Research Service · checked 2026-09-18 · independently re-checked
8. fib-e1-20 · Position of an expert body · federal rulemaking
   Therefore, we are not proposing to set a DRV for either soluble fiber or insoluble fiber.
   FDA, Food Labeling: Revision of the Nutrition and Supplement Facts Labels (proposed rule), 79 FR 11879 · checked 2026-09-18 · independently re-checked
9. fib-e1-04 · Observational data · systematic review of in vivo and clinical studies
   The results showed no significant correlations between consumption of dietary fiber to iron absorption/status-related biomarkers.
   Critical Reviews in Food Science and Nutrition, 2023 · checked 2026-09-18 · independently re-checked
10. fib-e1-26 · Meta-analysis or systematic review · systematic review of randomised trials, agency report
    Fiber ingested in food form had stronger associations than fiber ingested as supplements.
    Fiber Intake and Laxation in People With Normal Bowel Function: Systematic Review, AHRQ, 2025 · checked 2026-09-18 · independently re-checked
11. fib-e1-21 · Observational data · systematic review and meta-analysis of dietary surveys
    The mean amount of fiber provided to residents was 21.4 g/d [standard error (SE): 1.2; 95% confidence interval: 18.8, 24.2 g/d], the mean amount of fiber consumed by residents was 15.8 g/d (SE: 0.6; 95% confidence interval: 14.7, 16.9 g/d).
    American Journal of Clinical Nutrition, 2024 · checked 2026-09-18 · independently re-checked
12. fib-e1-22 · Observational data · scoping review of randomised controlled trials
    For ITFs, the fiber dosage ranged from 2.4 to 15.0 g/d. Psyllium dosages ranged from 6.0 to 25.0 g/d.
    Current Developments in Nutrition, 2024 · checked 2026-09-18 · independently re-checked
13. fib-e1-25 · Observational data · scoping review of randomised controlled trials
    Postprandial glycemia/insulinemia or colonic transit time were not studied at all in this population.
    Current Developments in Nutrition, 2024 · checked 2026-09-18 · independently re-checked
14. fib-e1-37 · Observational data · cross-sectional national survey
    This representative sample of 32,118 individuals aged 1-18 y reported inadequate intake of key nutrients including dietary fiber, eicosapentaenoic acid, docosahexaenoic acid, vitamin D, and vitamin E.
    Journal of Nutrition, 2026 · checked 2026-09-18 · independently re-checked
15. fib-t1 · Observational data · systematic review and meta-analysis of prospective studies
    Observational data suggest a 15-30% decrease in all-cause and cardiovascular related mortality, and incidence of coronary heart disease, stroke incidence and mortality, type 2 diabetes, and colorectal cancer when comparing the highest dietary fibre consumers with the lowest consumers
    Reynolds et al., The Lancet, 2019 · checked 2026-09-16 · independently re-checked
16. fib-t2 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised trials
    Clinical trials show significantly lower bodyweight, systolic blood pressure, and total cholesterol when comparing higher with lower intakes of dietary fibre. Risk reduction associated with a range of critical outcomes was greatest when daily intake of dietary fibre was between 25 g and 29 g.
    Reynolds et al., The Lancet, 2019 · checked 2026-09-16 · independently re-checked
17. fib-t3 · Observational data · umbrella review
    Convincing evidence (Class I) was identified for cardiovascular disease (CVD) mortality, pancreatic cancer, and diverticular disease. Highly suggestive evidence (Class II) supported associations with all-cause mortality, CVD, coronary heart disease and ovarian cancer.
    Veronese et al., Clinical Nutrition, 2025 · checked 2026-09-16 · independently re-checked
18. fib-t4 · Meta-analysis or systematic review · systematic review and meta-analysis
    Increased fibre intakes reduced glycated haemoglobin (HbA1c; mean difference [MD] -2.00 mmol/mol, 95% CI -3.30 to -0.71 from 33 trials), fasting plasma glucose (MD -0.56 mmol/L, 95% CI -0.73 to -0.38 from 34 trials)
    Reynolds et al., PLOS Medicine, 2020 · checked 2026-09-16 · independently re-checked
19. fib-t5 · Meta-analysis or systematic review · systematic review and meta-analysis
    High certainty evidence from trials of adults with hypertension indicates increasing fibre intakes reduces systolic (MD 4.3 mmHg (95% CI 2.2 to 5.8)) and diastolic blood pressure (MD 3.1 mmHg (95% CI 1.7 to 4.4)).
    Reynolds et al., BMC Medicine, 2022 · checked 2026-09-16 · independently re-checked
20. fib-t6 · Meta-analysis or systematic review · systematic review and meta-analysis
    Overall, 311 of 473 (66%) participants responded to fiber treatment and 134 of 329 (41%) responded to control treatment [RR: 1.48 (95% CI: 1.17, 1.88; P = 0.001); I2 = 57% (P = 0.007)], with psyllium and pectin having significant effects.
    van der Schoot et al., American Journal of Clinical Nutrition, 2022 · checked 2026-09-16 · independently re-checked
21. fib-r2-1 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised trials
    Fiber increased stool frequency [SMD: 0.72 (95% CI: 0.36, 1.08; P = 0.0001); I2 = 86% (P < 0.00001)]; psyllium and pectin had significant effects, and improvement was apparent only with higher fiber doses and greater treatment durations (≥4 weeks). Fiber improved stool consistency (SMD: 0.32; 95% CI: 0.18, 0.46; P < 0.0001), particularly with higher fiber doses.
    van der Schoot et al., American Journal of Clinical Nutrition, 2022 · checked 2026-09-17 · independently re-checked
22. fib-r5-2 · Observational data · dose-response meta-analysis of prospective cohort studies
    We identified 17 prospective cohort studies of dietary fiber intake and risk of type 2 diabetes involving 19,033 cases and 488,293 participants...A nonlinear relationship was found of total dietary fiber intake with risk of type 2 diabetes (P for nonlinearity < 0.01), and the RRs (95 % CI) of type 2 diabetes were 0.98 (0.90-1.06), 0.97 (0.87-1.07), 0.89 (0.80-0.99), 0.76 (0.65-0.88), and 0.66 (0.53-0.82) for 15, 20, 25, 30, and 35 g/day.
    Yao et al., European Journal of Epidemiology, 2014 · checked 2026-09-17 · independently re-checked
23. fib-r5-4 · Observational data · meta-analysis of prospective cohort studies
    Eighteen studies involving 672,408 individuals were finally included in the present study. The pooled-adjusted RRs of coronary heart disease for the highest versus lowest category of fiber intake were 0.93 (95% confidence interval (CI), 0.91-0.96, P < 0.001) for incidence of all coronary events and 0.83 (95% CI, 0.76-0.91, P < 0.001) for mortality.
    Wu et al., Clinical Nutrition, 2015 · checked 2026-09-17 · independently re-checked
24. fib-r5-5 · Observational data · meta-analysis of prospective cohort studies
    Eleven prospective studies involving 325,627 participants were included in the meta-analysis. The pooled RR of stroke for the highest compared with the lowest dietary fiber consumption was 0.83 (95 % CI 0.74, 0.93)...Moreover, there was a trend toward an inverse association between higher fiber consumption and stroke mortality (RR 0.85; 95 % CI 0.60, 1.20), although it is not significant.
    Zhang et al., European Journal of Epidemiology, 2013 · checked 2026-09-17 · independently re-checked
25. fib-t8 · Observational data · systematic review and meta-analysis of prospective studies
    Dose-response curves suggested that higher intakes of dietary fibre could confer even greater benefit to protect against cardiovascular diseases, type 2 diabetes, and colorectal and breast cancer. Similar findings for whole grain intake were observed.
    Reynolds et al., The Lancet, 2019 · checked 2026-09-16 · independently re-checked
26. fib-t9 · Observational data · systematic review and meta-analysis of prospective studies
    Smaller or no risk reductions were found with the observational data when comparing the effects of diets characterised by low rather than higher glycaemic index or load.
    Reynolds et al., The Lancet, 2019 · checked 2026-09-16 · independently re-checked
27. fib-e1-01 · Randomised controlled trial(s) · review of intervention trials with weighted regression
    The slope of the regression coefficients for cereal dietary fibers was 2.17 (95% CI: 1.99–2.35; p < 0.0001) compared to 2.03 (95% CI: 1.59–2.46; p < 0.0001) for vegetable dietary fiber.
    de Vries et al., Nutrients, 2016 · checked 2026-09-18 · independently re-checked
28. fib-e1-02 · Randomised controlled trial(s) · review of intervention trials with weighted regression
    The slope of the regression coefficients for fermentable fibers was 0.89 (95% CI: 0.72–1.04; p < 0.0001). For non-fermentable fibers, it was 2.88 (95% CI: 2.71–3.04; p < 0.0001).
    de Vries et al., Nutrients, 2016 · checked 2026-09-18 · independently re-checked
29. fib-e1-03 · Observational data · systematic review of randomised controlled trials
    Our findings suggest that the metabolic effects of galactomannans are source-dependent, with fenugreek-based interventions appearing to have greater potential for improving glycemic outcomes, while guar gum may be more effective in improving lipid parameters.
    Nutrients, 2026 · checked 2026-09-18 · independently re-checked
30. fib-e1-05 · Randomised controlled trial(s) · randomised controlled trial
    A 1-y supplementation with SCF results in higher whole-body BMC and BMD than placebo in girls only.
    American Journal of Clinical Nutrition, 2026 · checked 2026-09-18 · independently re-checked
31. fib-e1-06 · Randomised controlled trial(s) · randomised crossover trial
    The foil was removed, and the potato was placed in a sealed container and stored at 4 °C for five days.
    Nutrients, 2019 · checked 2026-09-18 · independently re-checked
32. fib-e1-07 · Randomised controlled trial(s) · randomised crossover trial
    Blood glucose area under the curve (AUC) was lower after coarse than fine and commercial oat flours (P < 0.03), and after whole than fine oat flour (P < .002).
    Nutrition Research, 2024 · checked 2026-09-18 · independently re-checked
33. fib-e1-08 · Randomised controlled trial(s) · randomised crossover trial
    Although whole grain wheat foods provide other health benefits, they did not in their natural composition confer lower postprandial glycemia or gastric emptying than their refined wheat counterparts.
    American Journal of Clinical Nutrition, 2022 · checked 2026-09-18 · independently re-checked
34. fib-e1-14 · Meta-analysis or systematic review · systematic review and Bayesian meta-regression of randomised trials
    Findings, such that each g/d of fiber softens stool by a mean of 0.013 units on the BSS, may be statistically significant, but are likely of little importance to most individuals.
    Balk et al., American Journal of Clinical Nutrition, 2026 · checked 2026-09-18 · independently re-checked
35. fib-e1-15 · Meta-analysis or systematic review · systematic review and network meta-analysis
    NMA suggested that viscous soluble fibers were associated with greater efficacy compared with placebo in relieving defecation difficulty (high certainty, class 1), and were also associated with improvements in stool consistency and stool frequency relative to placebo (moderate certainty, class 1).
    Food & Function, 2026 · checked 2026-09-18 · independently re-checked
36. fib-e1-17 · Randomised controlled trial(s) · review of intervention trials with weighted regression
    When transit time is already optimal, i.e., between 24 and 48 h, additional dietary fiber does not appear to alter it.
    de Vries et al., Nutrients, 2016 · checked 2026-09-18 · independently re-checked
37. fib-e1-18 · Meta-analysis or systematic review · systematic review of randomised intervention studies
    Overall, most fiber types did not show significant effects on appetite ratings and energy intakes.
    Appetite, 2023 · checked 2026-09-18 · independently re-checked
38. fib-e1-19 · Meta-analysis or systematic review · systematic review of randomised intervention studies
    Viscous fibers were more likely to improve appetite ratings compared to non-viscous fibers, and fermentability did not appear to affect appetite ratings.
    Appetite, 2023 · checked 2026-09-18 · independently re-checked
39. fib-e1-23 · Meta-analysis or systematic review · stated evidence gap in a systematic review
    Notably, no study effectively addressed the research question of this review, the overall effect of dietary fiber on laxation across a wide range of fiber intake amounts and in different types of fibers.
    Balk et al., American Journal of Clinical Nutrition, 2026 · checked 2026-09-18 · independently re-checked
40. fib-e1-24 · Meta-analysis or systematic review · stated evidence gap in a systematic review
    When fibers were incorporated into foods (muffins, oatmeal), it was frequently unclear either how much actual fiber was added to participants’ diets or what their background fiber intake was.
    Balk et al., American Journal of Clinical Nutrition, 2026 · checked 2026-09-18 · independently re-checked
41. fib-e1-27 · Meta-analysis or systematic review · systematic review of randomised trials, agency report
    The effect of additional fiber on rates of constipation (in people entering trials normal bowel function) is unclear.
    Fiber Intake and Laxation in People With Normal Bowel Function: Systematic Review, AHRQ, 2025 · checked 2026-09-18 · independently re-checked
42. fib-e1-28 · Observational data · umbrella review of meta-analyses of observational studies
    Convincing evidence (Class I) was identified for cardiovascular disease (CVD) mortality, pancreatic cancer, and diverticular disease.
    Clinical Nutrition, 2025 · checked 2026-09-18 · independently re-checked
43. fib-e1-29 · Observational data · umbrella review of meta-analyses of observational studies
    Overall, 3 of 21 (14%) outcomes presented convincing evidence (pancreatic cancer, CVD mortality, and all-cause mortality), but only CVD and all-cause mortality were based on prospective studies.
    Veronese et al., American Journal of Clinical Nutrition, 2018 · checked 2026-09-18 · independently re-checked
44. fib-e1-33 · Randomised controlled trial(s) · systematic review and meta-analysis
    Models showed 39% lower risk of gastrointestinal (GI) complications overall for fiber compared with nonfiber groups (pooled RR: 0.61; 95% CI, 0.47-0.79) but no group differences for individual GI complications, mortality, and intensive care unit or hospital length of stay.
    Journal of Parenteral and Enteral Nutrition, 2021 · checked 2026-09-18 · independently re-checked
45. fib-e1-34 · Meta-analysis or systematic review · systematic review of randomised controlled trials
    However, it is worth noting that the highest graded placebo-controlled psyllium study (54) revealed no significant benefit over placebo and head-to-head trials revealed that psyllium is less effective than comparator agents (e.g., PEG, lactulose, and fruits).
    Rao et al., American Journal of Gastroenterology, 2021 · checked 2026-09-18 · independently re-checked
46. fib-e1-35 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised trials
    Prebiotics do not improve gastrointestinal symptoms or QoL in patients with IBS or other FBDs, but they do increase bifidobacteria.
    Wilson et al., American Journal of Clinical Nutrition, 2019 · checked 2026-09-18 · independently re-checked
47. fib-e1-36 · Randomised controlled trial(s) · stated evidence gap in a systematic review
    Experts in the field caution against using fiber during EN because of perceived adverse patient outcomes; however, a comprehensive assessment of this topic is not evident to date.
    Journal of Parenteral and Enteral Nutrition, 2021 · checked 2026-09-18 · independently re-checked
48. fib-e1-38 · Observational data · umbrella review of meta-analyses of observational studies
    Thirty-three meta-analyses covering 38 health outcomes and 17,155,277 individuals were included. Of these, 29 (76 %) reported significant inverse associations (p < 0.05) between higher fiber intake and disease risk.
    Clinical Nutrition, 2025 · checked 2026-09-18 · independently re-checked
49. fib-t7 · Meta-analysis or systematic review · systematic review and meta-analysis
    Flatulence was higher in fiber groups compared to control groups(SMD: 0.80; 95% CI: 0.47, 1.13; P < 0.00001).
    van der Schoot et al., American Journal of Clinical Nutrition, 2022 · checked 2026-09-16 · independently re-checked
50. fib-e1-16 · Position of an expert body · guideline recommendation
    With the exception of increased risk of endometrial cancer with higher intakes of dietary fibre (very low certainty evidence), no undesirable effects were identified with dietary fibre intakes of at least 25 g per day, and no mitigating factors were identified that would argue against dietary fibre intake at this level.
    WHO, Carbohydrate intake for adults and children: WHO guideline, 2023 · checked 2026-09-18 · independently re-checked
51. fib-e1-30 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised trials
    However, flatulence severity was improved by prebiotics at doses ≤6 g/d (SMD: -0.35; 95% CI: -0.71, 0.00; P = 0.05) and by non-inulin-type fructan prebiotics (SMD: -0.34; 95% CI: -0.66, -0.01; P = 0.04), while inulin-type fructans worsened flatulence (SMD: 0.85; 95% CI: 0.23, 1.47; P = 0.007).
    Wilson et al., American Journal of Clinical Nutrition, 2019 · checked 2026-09-18 · independently re-checked
52. fib-e1-31 · Meta-analysis or systematic review · systematic review of randomised controlled trials
    Soluble fibers (psyllium, inulin, and polydextrose) seem safe and well tolerated. Abdominal distension/pain and flatulence were the most common adverse events and were mild to moderate in nature.
    Rao et al., American Journal of Gastroenterology, 2021 · checked 2026-09-18 · independently re-checked
53. fib-e1-32 · Meta-analysis or systematic review · systematic review of randomised controlled trials
    The doses of psyllium varied substantially in these studies, ranging from 3.5 g/d to 11 g twice daily.
    Rao et al., American Journal of Gastroenterology, 2021 · checked 2026-09-18 · independently re-checked