Soluble fibre
Binds bile acids in the gut and thereby lowers LDL and ApoB. The lever with the best ratio of effect to effort when blood lipids are the main topic.
Order of magnitude
Five to ten grams of viscous soluble fibre per day, reached consistently and spread across the day. That is not the same as the total fibre figure on the packet.
The effect requires daily intake and does not persist when the fibre is stopped. HDL does not change measurably. There is no uric-acid row. Ferritin is not reliably lowered by these fibres. Dose-response is disputed: Brown 1999 linear per gram, Whitehead 2014 no extra benefit above 3 g oat beta-glucan. The table shows rolled oats with the USDA beta-glucan figure, because BLS does not list beta-glucan separately.
Effects in detail
Each row is a directed edge from our database, with range, latency, evidence grade and the condition under which it applies at all.
| Marker | Effect | Latency | Mode of action | Outcome | Evidence | Condition | Sources |
|---|---|---|---|---|---|---|---|
| Apolipoprotein B | helps. Lowers Direction known, size not established the larger reduction is about 10 g/day of psyllium and the smaller about 3.5 g/day of oat beta-glucan One of the few dietary levers with direct ApoB evidence, not just LDL-C. Three meta-analyses sit at −3 to −5 mg/dL. | 3–3 weeks | chronic | unclear | Evidence grade A | applies regardless of the starting value | |
| LDL cholesterol | helps. Lowers Direction known, size not established the larger reduction is about 10 g/day of psyllium and the smaller about 3.5 g/day of oat beta-glucan, so the dose decides where in the range a person lands LDL-C proxy from meta-analyses of viscous fibre (about −7 to −13 mg/dL at 3.5 to 10 g/day). The effect is larger at higher baseline LDL and in diabetes. Trial proxy: ldl_c. | 3–3 weeks | chronic | unclear | Evidence grade A | applies regardless of the starting value | |
| HOMA-IR | helps. Lowers -0.38 HOMA-IR units confidence interval of the estimate, not the range one person can expect Estimate for adults with overweight without diabetes at an assumed baseline of 3.0. In type 2 diabetes the effect at a higher dose is much larger. HOMA-IR was not an outcome endpoint. | 4–4 weeks | postprandial and chronic | no | Evidence grade B | applies regardless of the starting value | |
| Triglycerides | helps. Lowers -5.60 mg/dL confidence interval of the estimate, not the range one person can expect The lower bound of zero percent is intentional: Ghavami 2023 finds a small reduction, Whitehead 2014 and Brown 1999 none. Best described as little or no effect on triglycerides. | not specified | chronic | no | Evidence grade C | applies regardless of the starting value | |
| Diastolic blood pressure | helps. Lowers -0.39 mmHg confidence interval of the estimate, not the range one person can expect Twenty-two randomised trials in 1430 adults give a systolic reduction of 1.59 mmHg (95 % CI -2.72 to -0.46) and a diastolic reduction of 0.39 mmHg with viscous soluble fibre. Substantial heterogeneity (I2 72 % systolic, 67 % diastolic) and a diastolic confidence interval that only just excludes zero. | 4–4 weeks | chronic | unclear | Evidence grade A | applies regardless of the starting value | |
| Systolic blood pressure | helps. Lowers -1.59 mmHg confidence interval of the estimate, not the range one person can expect Twenty-two randomised trials in 1430 adults give a systolic reduction of 1.59 mmHg (95 % CI -2.72 to -0.46) and a diastolic reduction of 0.39 mmHg with viscous soluble fibre. Substantial heterogeneity (I2 72 % systolic, 67 % diastolic) and a diastolic confidence interval that only just excludes zero. | 4–4 weeks | chronic | unclear | Evidence grade A | applies regardless of the starting value | |
| HbA1c | helps. Lowers -0.63 percentage points of HbA1c confidence interval of the estimate, not the range one person can expect Twenty-nine randomised trials in 1517 people with type 2 diabetes give an HbA1c reduction of 0.63 percentage points (95 % CI -0.90 to -0.37), together with fasting glucose -0.89 mmol/L and HOMA-IR -0.58 standardised units. This is one of the larger dietary HbA1c effects in the database and it sits at exactly the dose the batch-1 fibre lever already recommends for LDL-C, so the two effects come free with each other. | not specified | chronic | unclear | Evidence grade A | applies regardless of the starting value |
What this measure costs
Counteracting effects of the same measure.
No counteracting effect is on file for this measure. That does not mean there is none, only that we found no defensible edge.
Moves without implying progress
Informational or no established effect: the marker moves or was checked, and that is not progress.
| Marker | Effect | Latency | Mode of action | Outcome | Evidence | Condition | Sources |
|---|---|---|---|---|---|---|---|
| Ferritin | checked, nothing happens. No established effect A systematic review of 32 studies (9 human) found no significant relationship between fibre intake and iron absorption or iron-status markers. Grade C: mostly animal data and indirect fibre types. | not specified | chronic | no | Evidence grade C | applies regardless of the starting value | |
| HDL cholesterol | checked, nothing happens. No established effect Both the oat beta-glucan meta-analysis (28 RCTs) and the multi-fibre meta-analysis (67 trials) report no change in HDL-C. Included as a 'no effect' row. | not specified | chronic | no | Evidence grade A | applies regardless of the starting value | |
| high-sensitivity CRP | moves, and does not count. Lowers -0.37 mg/L confidence interval of the estimate, not the range one person can expect Fourteen randomised trials of fibre or fibre-rich food in overweight and obese adults gave a CRP reduction of 0.37 mg/L (95 % CI -0.74 to 0), with no obvious heterogeneity and no publication bias. The interval touches zero, so the point estimate of -0.37 mg/L rests on the 8 g/day subgroup. | not specified | chronic | unclear | Evidence grade B | applies regardless of the starting value |
Food sources
What you would have to eat to reach the stated order of magnitude, and what comes along with it.
| Food | Content per 100 g | Amount per week | Added burden |
|---|---|---|---|
| Psyllium husk No BLS row. The highest content per gram in this table, but it requires markedly more fluid. 70 g viscous fibre per 100 g remains a typical label figure. | 70.0 g | 100 gequals 10 × | no relevant added burden on file |
| Rolled oats BLS C133000, oat flakes. 11.0 g total fibre and 4.8 g water-soluble fibre per 100 g. The measure table keeps the USDA beta-glucan figure of 7.52 g, because BLS does not list beta-glucan separately. | 7.5 g | 930 gequals 16 × |
|
Sources
Full details of every study the rows above rely on.
Cholesterol-lowering effects of oat beta-glucan: a meta-analysis of randomized controlled trials
Whitehead et al. · American Journal of Clinical Nutrition · 2014 · Meta-analysis
The effect of oat beta-glucan on LDL-cholesterol, non-HDL-cholesterol and apoB for CVD risk reduction: a systematic review and meta-analysis of randomised-controlled trials
Ho et al. · British Journal of Nutrition · 2016 · Meta-analysis
Cholesterol-lowering effects of dietary fiber: a meta-analysis
Brown, Rosner, Willett, Sacks · American Journal of Clinical Nutrition · 1999 · Meta-analysis
Effect of psyllium (Plantago ovata) fiber on LDL cholesterol and alternative lipid targets, non-HDL cholesterol and apolipoprotein B: a systematic review and meta-analysis of randomized controlled trials
Jovanovski et al. · American Journal of Clinical Nutrition · 2018 · Meta-analysis
Soluble Fiber Supplementation and Serum Lipid Profile: A Systematic Review and Dose-Response Meta-Analysis of Randomized Controlled Trials
Ghavami et al. · Advances in Nutrition · 2023 · Meta-analysis
Effects of isolated single fibers, fiber mixtures, and fiber-rich whole foods on glucose homeostasis in individuals with overweight and obesity: A systematic review and meta-analysis
Colak et al. · Clinical Nutrition · 2025 · Meta-analysis
Effect of low glycaemic index or load dietary patterns on glycaemic control and cardiometabolic risk factors in diabetes: systematic review and meta-analysis of randomised controlled trials
Chiavaroli et al. · BMJ · 2021 · Meta-analysis
Bundeslebensmittelschlüssel (BLS), Version 4.0 – Deutsche Nährstoffdatenbank
Max Rubner-Institut · 2025 · Reference data
Official German nutrient database, open data CC BY 4.0. Values per 100 g edible portion. Attribute the Max Rubner-Institut as publisher.
Effect of dietary fiber on circulating C-reactive protein in overweight and obese adults: a meta-analysis of randomized controlled trials
Jiao et al. · International Journal of Food Sciences and Nutrition · 2015 · Meta-analysis
Should Viscous Fiber Supplements Be Considered in Diabetes Control? Results From a Systematic Review and Meta-analysis of Randomized Controlled Trials
Jovanovski et al. · Diabetes Care · 2019 · Meta-analysis
The effect of viscous soluble fiber on blood pressure: a systematic review and meta-analysis of randomized controlled trials
Khan et al. · Nutrition, Metabolism and Cardiovascular Diseases · 2018 · Meta-analysis
Effects of dietary fiber on intestinal iron absorption, and physiological status: a systematic review of in vivo and clinical studies
Verediano et al. · Critical Reviews in Food Science and Nutrition · 2023 · Review
Effects of soluble fiber supplementation on glycemic control in adults with type 2 diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials
Xie et al. · Clinical Nutrition · 2021 · Meta-analysis