Fiber

Other tracked

Gut · satiety

Your intake

Today (logged)

0 g

0% of 28 g

Stack potential

0 g

0% of 28 g

Target

28 g

FDA Daily Value

Where you are on the ladder0% of target

What each level of fiber does

Approximate dose-response bands. Individual response varies — these are starting points, not prescriptions.

Severely lowYOU ARE HERE
0 g – 9.24 g
Constipation, poor microbiome diversity, blood-sugar swings.
Insufficient
9.24 g – 28 g
Only ~5% of US adults hit 28 g/day. Add legumes, whole grains, vegetables, psyllium.
Adequate
28 g – 42 g
DV (28 g) met. Microbiome-fermentable fiber especially valuable.
Therapeutic
42 g – 56 g
Higher intake helps cholesterol, glycemic control, satiety.
Diminishing returns
56 g – +
Past the point where extra intake typically helps. Evidence for further benefit is thin.

Overview

Indigestible plant carbohydrates. Soluble fiber (psyllium, beta-glucan, pectin) forms gels that lower cholesterol and slow glucose absorption; insoluble fiber (wheat bran, cellulose) bulks stool and speeds transit. Median US intake is ~16 g/day vs 25–38 g recommended — the gap is one of the most consequential dietary deficits, with effects on metabolic, cardiovascular, and microbiome health.

Functions

●Slows gastric emptying and glucose absorption (soluble)
●Lowers LDL cholesterol via bile acid sequestration (soluble)
●Bulks stool, speeds transit (insoluble)
●Feeds gut bacteria → short-chain fatty acids (butyrate, propionate, acetate)
●Increases satiety via gut-brain signalling

Mechanism

Soluble fiber binds bile acids in the gut; the liver pulls cholesterol to synthesise replacement bile, lowering LDL. Gel formation slows nutrient absorption, blunting postprandial glucose spikes. Bacterial fermentation of fiber produces short-chain fatty acids — butyrate is the primary fuel for colonocytes and signals via GPR43/41 to reduce inflammation, improve insulin sensitivity, and support gut barrier integrity.

Benefits

●Reduces LDL cholesterol 5–10% (psyllium 10+ g/day)
●Improves glycemic control in type 2 diabetes
●Reduces colorectal cancer risk (10–15% per 10 g/day; large cohorts)
●Increases satiety, supports weight management
●Improves bowel regularity and reduces diverticulosis
●Supports microbiome diversity and butyrate production
●Reduces all-cause mortality 15–30% per 10 g/day (Reynolds Lancet 2019)

Deficiency

Inadequate intake (<25 g/day) is the modern norm. Drives constipation, dysbiosis, and over decades contributes to metabolic and colon disease.

Signs

●Constipation, small infrequent stools
●Elevated LDL, postprandial glucose
●Reduced microbiome diversity
●Increased hunger, lower satiety per meal

At-risk groups

●Standard American Diet consumers
●Low-carb / carnivore diets
●Children with picky eating
●Older adults (chewing difficulties)

Excess

Rapid increases cause bloating and gas; high intake in IBS or with limited fluid can trigger discomfort. Insoluble fiber may worsen flares in active IBD.

Signs

●Bloating, gas, abdominal discomfort
●Loose stools or constipation (paradoxical, fluid-dependent)
●Reduced mineral absorption at very high phytate intake
●Possible obstruction with inadequate fluid + very high intake (rare)

Forms

Psyllium husk
Best-studied soluble fiber; LDL and bowel regularity; ~10 g/day
Beta-glucan (oat / barley)
FDA heart-health claim; LDL-lowering
Inulin / FOS
Prebiotic; feeds Bifidobacteria; FODMAP — can worsen IBS
Methylcellulose
Semi-synthetic soluble; gentle bulk; non-fermenting
Wheat dextrin
Soluble, neutral taste, well-tolerated
Whole-food fiber
Comes packaged with vitamins, polyphenols, varied fiber types — always the first choice

Food sources

Black beans (cooked) · 1/2 cup7.5 g
Lentils (cooked) · 1/2 cup8 g
Avocado · 1 medium10 g
Raspberries · 1 cup8 g
Whole-wheat pasta (cooked) · 1 cup6 g
Chia seeds · 1 tbsp5 g

Supplement forms

Food first — fiber from whole foods comes with vitamins, polyphenols, and a mix of fiber types. If supplementing, psyllium husk is the best-studied for both LDL and bowel regularity. Inulin and FODMAP-rich fibers can worsen IBS symptoms in some. Start low (3–5 g) and ramp over weeks with adequate fluid to avoid bloating.

Bioavailability

Not absorbed in small intestine (definitional). Soluble fibers ferment in colon → SCFAs (the systemic benefits). Insoluble fibers pass largely intact, providing mechanical bulking. Adequate fluid intake (~30 mL/kg) is required for either type to work as intended.

Longevity relevance

One of the highest-leverage dietary inputs: Reynolds et al. (Lancet 2019) — every 8 g/day increase in dietary fiber associated with 5–27% reduction in all-cause mortality, CHD incidence, T2D incidence, and colorectal cancer across 185 prospective studies. The signal is consistent, dose-responsive, and unmatched by single supplements.

Relationships

Synergies (works better with)

Fermented foods / probiotics · Prebiotic fiber feeds the bacteria — synbiotic synergy
Polyphenols · Whole-plant pairings amplify each other's gut and metabolic effects
Adequate fluid · Bulk-forming fibers require water to function; inadequate fluid can cause obstruction

Antagonists (competes with / inhibited by)

Mineral absorption (phytate) · Very high intake reduces zinc, iron, calcium uptake; relevant in marginal diets
Drug timing · Bulk-forming fibers can reduce absorption of co-ingested drugs; separate by 1–2 hours