Dietary fiber and the risk of dying

In Reynolds 2019, each extra 8 grams of fiber a day was linked to about a 7% lower risk of dying, from any cause.

Read your number

Is my daily fiber intake good?

Use the age- and sex-based intake guidance as a starting point. The Institute of Medicine’s guidance is 38 grams a day for men and 25 for women through age 50; over 50, it is 30 for men and 21 for women. These are nutritional intake values. Reynolds 2019 studied a separate association between fiber intake and death rates; the intake floor does not change the score’s curve.

If you're 70 or older

At 70 and older, the over-50 intake values apply: 30 grams a day for men and 21 for women. Start with legumes, whole grains, vegetables or fruit, and increase gradually with plenty of water, as the guidance below suggests. Read the intake value as nutrition advice, separately from the mortality comparison.

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Evidence already on this page: Institute of Medicine, Food and Nutrition Board 2002; Reynolds et al. 2019.

Where you stand

Reynolds 2019 is the study behind the number: grams of fiber per day, risk of dying from any cause. The categorical peak sat at 25–29 g/day. The on-screen target is a gram floor. Age and sex only select that floor. They do not change the hazard.

Risk falls in a steady line as fiber goes up, all the way across the 5 to 35 grams the studies covered.

At 12 g1.04×a typical 45-year-old’s risk, about the same as typical.

See the same numbers as a table

Fiber and risk of death from any cause, as a multiple of a typical 45-year-old’s risk
Grams of fiber a day	Risk vs typical	In words
0 g	1.10×	a little higher than typical; beyond the studies, so this is the model’s estimate
10 g	1.06×	a little higher than typical
20 g	0.96×	about the same as typical
30 g	0.88×	lower than typical
40 g	0.84×	lower than typical; beyond the studies, so this is the model’s estimate

Risk of death from any cause, with every other marker held at typical. Drag the marker or use the arrow keys. Nothing you move here is saved.

Hatched areas are beyond the studies. The line there is the model’s estimate, or flat.

Source: Reynolds et al. 2019, The Lancet (PMID 30638909)

The study, not the score

highest vs lowest fibre intake

Reynolds et al. 2019

0.85 (0.79–0.91)

15% lower all-cause mortality

The bar shows the study’s 95% confidence interval, the range of values consistent with its data. The tick is the study’s best single figure. The centre line is no difference. The chart above is the score’s own curve, not this study.

What it is

Grams of dietary fiber in a day, from plant foods. The on-screen target is a gram floor (38/30/25/21 g). Age and sex only select that floor. Reynolds’s 25–29 g band is a different number, and the floor does not change the hazard.

How the score uses it

Technical notes

The curve is absolute grams per day from Reynolds et al. 2019: log-linear at RR 0.93 (0.90–0.95) per extra 8 g, HR 1.0 at 16 g/day (the median reference intake), flat outside about 5–35 g because that is the range the paper modelled. The 10-study highest-versus-lowest RR 0.85 (0.79–0.91) is that study’s categorical point estimate in people without chronic disease. It is not a curve floor at the gram target, and it is not the 185-publication count. Categorical benefit was greatest at 25–29 g/day. Main source: Reynolds. Supporting: Yao 2023 (highest-vs-lowest RR 0.81, 0.90 per 10 g) / Ramezani 2024 (headline 0.77 mixes sick cohorts; general-pop 0.82) / Mirrafiei 2023 (dose-response meta-analyses suggested an inverse association for total fibre; the abstract quotes no per-gram slope and no single highest-vs-lowest HR; fruit fibre was not associated with all-cause mortality; this slider is total grams). Interpolated interiors are constructed. The 38/30/25/21 g line is advice only.

How to improve it

Eat more legumes, whole grains, vegetables and fruit
Add ground flax or chia to meals
Increase gradually with plenty of water

What the studies found

Endpoint	Grade	Finding
All-cause mortality	B	+8g Rule (Reynolds 2019) Technical notes Assuming linearity, each extra 8 g of fibre/day was RR 0.93 (0.90–0.95) for all-cause death — about 7% lower. That is Figure 1A, not the T2D per-8 g estimate.
All-cause mortality	C	The 25–29g Zone (Reynolds 2019) Technical notes Categorical benefit was greatest at 25–29 g/day (6 of 7 critical outcomes). That contrast is not a dose-response. The separate per-8 g slope had no plateau. The calculator’s age/sex line is a gram floor, not that band, and it does not change the hazard.
All-cause mortality	B	Steeper Below 15g (Yao 2023) Technical notes Newer meta (search to Aug 2023, 16 studies): highest-vs-lowest fibre all-cause mortality RR 0.81 (0.77–0.86); per 10 g/day RR 0.90 (0.86–0.93) across 14 studies. Dose-response is non-linear, steeper below 15 g/day. This calculator’s curve does not use that kink. It is Reynolds’s per-8 g slope, with HR 1.0 at 16 g/day.
All-cause mortality	C	0.82 in General Population Only (Ramezani 2024) Technical notes Largest fibre-mortality pool to date: a 64-study review of 3,512,828 people, though the all-cause mortality meta itself is 33 reports. Overall highest-vs-lowest all-cause mortality HR was 0.77 (0.73–0.82), but the general-population subgroup (19 reports) was a smaller 0.82 (0.77–0.86) versus 0.67 (0.61–0.72) in cohorts with cancer, T2D, or CKD — mixing sick and healthy cohorts inflates the headline number.
All-cause mortality	B	Subtype Matters: Insoluble 0.77, Legume 0.93 (Mirrafiei 2023) Technical notes Across 28 prospective studies (1,613,885 people), most fibre subtypes were linked to lower all-cause mortality — insoluble fibre HR 0.77, legume fibre a smaller 0.93 — but fruit fibre showed no significant association. Dose-response meta-analyses in the abstract suggested an inverse association between total fibre and all-cause mortality. The abstract does not quote a per-gram slope, and it does not give one pooled total-fibre highest-vs-lowest HR.

What argues against this

Ramezani et al. 2024 (64-study review, 3,512,828 people) is the strongest opponent on magnitude: its general-population subgroup (19 reports) carried a smaller all-cause mortality benefit (HR 0.82, 0.77–0.86) than its own mixed overall estimate (HR 0.77), while cohorts with cancer, T2D, or CKD carried a much larger apparent benefit (HR 0.67, 0.61–0.72). This shows that pooling diseased and healthy cohorts inflates the headline fiber-mortality association above what a healthy general population actually experiences — it undercuts the size of the benefit claim, not its direction.

Last reviewed 12 October 2026

Sources

6 cited

Institute of Medicine, Food and Nutrition Board (2002) — National Academies
Report Offers New Eating and Physical Activity Targets To Reduce Chronic Disease Risk
View source
Reynolds et al. (2019) — The Lancet
Carbohydrate quality and human health: a series of systematic reviews and meta-analyses
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Yao et al. (2023) — Frontiers in Nutrition
Dietary intake of total vegetable, fruit, cereal, soluble and insoluble fiber and risk of all-cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies
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Ramezani et al. (2024) — Clinical Nutrition
Dietary fiber intake and all-cause and cause-specific mortality: An updated systematic review and meta-analysis of prospective cohort studies
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Mirrafiei et al. (2023) — Food & Function
Total and different dietary fiber subtypes and the risk of all-cause, cardiovascular, and cancer mortality: a dose-response meta-analysis of prospective cohort studies
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Yang et al. (2015) — American Journal of Epidemiology
Association between dietary fiber and lower risk of all-cause mortality: a meta-analysis of cohort studies
View source

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Educational content only — not medical advice, diagnosis, or treatment. Not a medical device; not FDA evaluated. Consult a qualified healthcare professional about your own health, and call emergency services for urgent symptoms. Full medical disclaimer →