Oat bran: the cholesterol effect is real and the size is known

This is one of the few foods where the cholesterol story survives contact with the evidence. Pooling 58 randomized trials in 3,974 people, a median 3.5 g a day of oat beta-glucan lowered LDL cholesterol by 7.3 mg/dL (0.19 mmol/L) and non-HDL cholesterol by 7.7 mg/dL (0.20 mmol/L) against control diets, with heterogeneity the authors could not explain (I2 79 percent for LDL). A separate meta-analysis of 28 trials at 3 g a day or more put LDL down 9.7 mg/dL (0.25 mmol/L) and total cholesterol down 12 mg/dL (0.30 mmol/L), with HDL and triglycerides unchanged and larger falls in people who started with higher LDL or had diabetes. That pooled set included in-house study reports from an oat ingredient company. When 55 trials of grains and brans were ranked against each other, oat bran came first at 0.35 mmol/L off total cholesterol and 12 mg/dL (0.32 mmol/L) off LDL, while wheat bran, barley and brown rice did not beat control, though that ranking rests on indirect comparisons. The label thresholds tell you how much of the food that means. In the US, oat bran must carry at least 5.5 percent beta-glucan and 16 percent total dietary fiber by dry weight, and a serving must deliver 0.75 g of soluble fiber. In the EU a portion needs 1 g of beta-glucan, and the claim has to tell the buyer that the effect comes at 3 g a day. Two cautions sit further down the page: ordinary oats are often contaminated with wheat, rye or barley, which matters in celiac disease, and oat bran has caused bowel blockage in published case reports.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• For the US heart-disease claim, oat bran must be at most 50% of the starting oat material and carry at least 5.5% beta-glucan soluble fiber and 16% total dietary fiber by dry weight. — US food labeling, 21 CFR 101.81(c) Evidence E source
  Definition threshold: 5.5% beta-glucan, 16% total dietary fiber (dwb), one third soluble
• USDA has no retention factor for oat bran and no selenium in the R6 table at all. The only cooking numbers are USDA's separate raw and cooked records, where cooked oat bran holds about one seventh of the thiamin per 3.5 oz (100 g) because of the water added. — USDA SR Legacy: Oat bran, raw (FDC 168872) and Oat bran, cooked; USDA R6 Cereal Grains and Pasta group (n = two USDA records) Evidence E source
  Thiamin 1.17 mg raw vs 0.16 mg cooked per 3.5 oz (100 g); selenium 45.2 vs 7.7 ug; phosphorus 734 vs 119 mg; R6 row for oat bran absent

What a real portion looks like

• Adding 3.6 oz (102 g) of oat bran a day (6 g soluble fiber) to a low-fiber diet for 2 weeks cut total cholesterol by 14% versus 4% on control in 24 young adults, and raised fecal energy loss by 37%. — 24 healthy adults aged about 25, double-blind randomized crossover, two 2-week periods (n = 24) Evidence B source
  TC -14% vs -4%; non-HDL-C -16% vs -3%; TG -21% vs -10%; energy excretion 1014 vs 638 kJ/day; body weight unchanged
• Each gram of oat beta-glucan from oat bran added to instant oatmeal cut the 2-hour glucose area by 7% and the peak rise by 15% in 40 people. A 20% smaller area needed 1.6 g, a 20% smaller peak only 0.4 g. — 40 healthy adults, randomized crossover, 27 g instant oatmeal with 247 g 2% milk plus 0 to 1.6 g oat beta-glucan (n = 40) Evidence B source
  IAUC -7% per g OBG (P = 0.009), peak rise -15% per g (P = 0.002); 1.6 g OBG: iAUC 74 vs 93 mmol min/L
• A US food may carry the soluble-fiber heart-disease claim only if a serving of the whole oat food supplies at least 0.75 g of soluble fiber. — US food labeling, 21 CFR 101.81(c) Evidence E source
  0.75 g soluble fiber per reference amount customarily consumed
• Under Regulation (EU) 432/2012 the cholesterol claim needs at least 1 g of beta-glucans per portion and tells consumers the effect comes with 3 g a day, while the post-meal glucose claim needs 4 g of beta-glucans per 30 g of available carbohydrate. — EU food labeling, conditions of use in the Annex to Regulation (EU) No 432/2012 Evidence E source
  Cholesterol claim: 1 g beta-glucans per quantified portion, 3 g/day; glucose claim: 4 g per 30 g available carbohydrate
• In FNDDS a cup of cooked oat bran cereal weighs 8.5 oz (240 g), and one ounce of dry oat bran yields about 150 g cooked, a five-fold swell from the water it takes up. — US household measures, FNDDS: Oat bran cereal, cooked (fdc_id 2708444) (n = one FNDDS food) Evidence E source
  1 cup cooked 240 g; 1 cup dry yields 500 g; 1 oz dry yields 150 g

What your body absorbs

• Despite its phytate, 5 oz (142 g) of oat bran a day for 21 days did not significantly lower fractional zinc absorption in 12 healthy adults, and more zinc was absorbed in total. — healthy subjects (6 men, 6 women), oat bran in bread at three main meals vs identical low-fiber diet, stable zinc isotopes (n = 12) Evidence C source
  Fractional zinc absorption 0.48 (low fiber) vs 0.40 (oat bran), P = 0.07; absorbed zinc 64 vs 99 micromol, P = 0.009
• Despite its phytate, 5 oz (142 g) of oat bran a day for 21 days did not measurably reduce fractional zinc absorption in 12 adults (0.40 vs 0.48, P = 0.07), and the extra zinc in the bran meant more zinc was absorbed in total. — 12 healthy adults (6 men, 6 women), two 21-day periods, low-fiber animal-protein diet with or without oat bran in bread, stable isotope 70Zn (n = 12) Evidence B source
  Fractional zinc absorption 0.48 vs 0.40 (P = 0.07); absorbed zinc 64 vs 99 umol (P = 0.009); phytate 0.5 vs 4.0 mmol per 10 MJ
• Drinking oat bran mixed in water before white bread lowered the glucose response in 10 healthy adults, with each gram of oat beta-glucan trimming the glucose area by about 4.35% and the peak by 6.57%. — 10 healthy adults, pilot crossover, preload of 4.5, 13.6 or 27.3 g oat bran (22% high molecular weight beta-glucan) in water before white bread (n = 10) Evidence B source
  Glucose AUC per g beta-glucan -4.35% (r 0.507, P = 0.0008), peak -6.57% (P < 0.0001); 27.3 g preload AUC lower than bread alone

What cooking and storage change

• The same 5 to 6 g a day of beta-glucan from oat bran lowered LDL by 10 mg/dL (0.26 mmol/L) (6.7%) when drunk in orange juice but not when baked into bread and cookies (4.6 mg/dL (0.12 mmol/L), not significant) in mildly hypercholesterolemic adults. — 48 mildly hypercholesterolemic adults (bread and cookies, 4 weeks) and 25 of them (juice, 2-week crossover) (n = 48 and 25) Evidence B source
  Bread and cookies: LDL change -4.6 mg/dL (-0.12 mmol/L) (P = 0.173); juice: LDL -10 mg/dL (-0.26 mmol/L) (6.7%, P = 0.001), TC/HDL ratio -0.26

What it does to your health

• A 2019 network meta-analysis of 55 trials with 3900 people ranked oat bran first among whole grains and brans, lowering LDL cholesterol by 12 mg/dL (0.32 mmol/L) and total cholesterol by 14 mg/dL (0.35 mmol/L) against control. — randomized trials of whole grains and brans (oat bran, oat, barley, brown rice, wheat, wheat bran) on blood lipids (n = 55 trials, 3900 participants) Evidence A source
  Oat bran vs control: TC -0.35 mmol/L (95% CI -0.47 to -0.23), LDL-C -12 mg/dL (-17 to -7.3; metric: -0.32 mmol/L, -0.44 to -0.19); oat second; barley, brown rice, wheat, wheat bran ineffective
• In a 6-week randomized dose trial of 156 adults with high LDL cholesterol, 2 oz (56 g) of oat bran a day lowered LDL by 15.9% against a farina control, more than the same weight of oatmeal. — adults with LDL-C above 160 mg/dL (4.14 mmol/L), or 130-160 mg/dL (3.37-4.14 mmol/L) with multiple risk factors; oatmeal or oat bran at 28, 56 or 84 g dry weight daily vs 28 g farina (n = 156) Evidence B source
  LDL-C -10.1% (84 g oatmeal), -15.9% (56 g oat bran), -11.5% (84 g oat bran) vs farina at week 6; 28 g doses not significant
• On a metabolic ward, 20 men with high cholesterol randomized to oat bran for 21 days cut LDL cholesterol by 12.1% while wheat bran on an otherwise identical diet had no significant effect. — hypercholesterolemic men on a metabolic ward, oat bran or wheat bran diets identical except for soluble fiber (n = 20) Evidence B source
  Oat bran: total cholesterol -12.8% (P < 0.001), LDL-C -12.1% (P < 0.004), apoB-100 -13.7%; wheat bran no significant effect
• Across 58 randomized trials with 3974 people, a median 3.5 g a day of oat beta-glucan lowered LDL cholesterol by 7.3 mg/dL (0.19 mmol/L) and non-HDL cholesterol by 7.7 mg/dL (0.20 mmol/L) versus control diets. — 3974 adults in 58 RCTs of at least 3 weeks, diets enriched with oat beta-glucan vs control (n = 3974 (58 trials)) Evidence A source
  LDL-C -7.3 mg/dL (95% CI -8.9 to -5.4; metric: -0.19 mmol/L, -0.23 to -0.14); non-HDL-C -0.20 (-0.26, -0.15); apoB -0.03 g/L

Safety, limits and interactions

• Across 17 trials of oat products in 1731 people with dyslipidemia, side effects were mostly gut symptoms, with diarrhea, nausea and flatulence the most common. — patients with dyslipidemia in RCTs of oat-based products including oat bran (n = 17 trials, 1731 subjects) Evidence A source
  Adverse events mostly gastrointestinal (diarrhea, nausea, flatulence); no difference in major cardiovascular events in one trial
• A meta-analysis of 40 food testing studies found gluten above 20 mg/kg in 15.12% of gluten-free foods, and oats were the most contaminated food. — labeled gluten-free, naturally gluten-free foods and food-service meals tested with validated methods (n = 40 studies) Evidence C source
  Gluten above 20 mg/kg in 15.12% (95% CI 9.56 to 21.70%); oats the most contaminated food
• A 1989 case report describes small-bowel obstruction caused by a bezoar, a solid mass, of oat bran. — patient with small-bowel obstruction, details not in the corpus record Evidence D source
  Small-bowel obstruction caused by an oat-bran bezoar
• The FDA-approved levothyroxine label says dietary fiber may bind the drug and lower its absorption from the gut. — people taking levothyroxine Evidence E source
  Dietary fiber may bind levothyroxine and lower its absorption
• In hypothyroid patients who needed unusually high levothyroxine doses, stopping a fiber supplement lowered the dose they needed, and in lab tests wheat bran bound the drug. — adult hypothyroid patients needing unusually high levothyroxine doses who took a fiber supplement Evidence D source
  Levothyroxine need fell when fiber supplements were stopped; wheat bran adsorbed levothyroxine in vitro, dose dependently
• In 17 randomized trials with 1731 people with dyslipidemia, oat-based products including oat bran lowered LDL by 9.3 mg/dL (0.24 mmol/L) versus placebo or usual diet, and the reported side effects were gastrointestinal (diarrhea, nausea, flatulence). — 1731 patients with dyslipidemia in 17 RCTs of at least 4 weeks, oat beta-glucan, oat bran or wholegrain oat products (n = 1731 (17 trials)) Evidence A source
  LDL-C WMD -9.3 mg/dL (95% CI -13 to -5.8; metric: -0.24 mmol/L, -0.33 to -0.15), TC -0.32 (-0.48, -0.17), moderate certainty; HDL and TG little effect; one study, no difference in major CV events

What people believe that the data does not support

• FDA allows the heart health claim for oat soluble fiber only in diets that supply 3 g or more of beta-glucan a day from whole oats or barley, a source group that includes oat bran. — 21 CFR 101.81(c), soluble fiber from certain foods and coronary heart disease Evidence E source
  Qualifying intake: 3 g/day or more of beta-glucan soluble fiber from whole oats or barley
• The EU authorizes the health claim that oat beta-glucan has been shown to lower blood cholesterol. — EU Register of nutrition and health claims, claim POL-HC-6248 Evidence E source
  Authorized
• In a network meta-analysis of 55 trials with 3900 people, oat bran ranked first for lowering total cholesterol (14 mg/dL (0.35 mmol/L)) and LDL (12 mg/dL (0.32 mmol/L)), ahead of whole oats, while wheat bran, barley and brown rice did not beat control. — 3900 adults in 55 trials of whole grains and brans, pairwise and network meta-analysis (n = 3900 (55 trials)) Evidence A source
  Oat bran: TC -0.35 mmol/L (95% CI -0.47, -0.23), LDL-C -0.32 (-0.44, -0.19); oat: TC -0.26, LDL -0.17; wheat bran ineffective
• In 18 randomized trials with 1024 people, whole oats and oat bran (20 to 136 g a day) lowered HbA1c, fasting glucose and fasting insulin, while beta-glucan extracts on their own did not. — 1024 people with type 2 diabetes, hyperlipidemia or overweight in 18 RCTs of at least 4 weeks (n = 1024 (18 trials)) Evidence A source
  Oats: HbA1c down (P < 0.001, I2 0%), fasting glucose down (P < 0.001, I2 68%), fasting insulin in T2D down; extracts: no decrease
• The EU register authorizes the claim that oat beta-glucan has been shown to lower or reduce blood cholesterol, a stronger wording than the generic beta-glucan maintenance claim. — EU food labeling Evidence E source
  Authorized Article 14 style claim; conditions in Regulation 432/2012
• The EU register also authorizes the claim that beta-glucans from oats or barley eaten as part of a meal reduce the blood glucose rise after that meal. — EU food labeling Evidence E source
  Authorized claim; conditions in Regulation 432/2012
• A branded oat bran claim that 3 g of its oat beta-glucan a day helps maintain healthy blood glucose levels is non-authorized in the EU register, so a product cannot promise glucose control from oat bran on the label. — EU food labeling Evidence E source
  Non-authorized claim (CalorieControl Trim Oat Bran)

Who this works differently for

• In a 2024 meta-analysis of 17 randomized trials with 1731 people with dyslipidemia, oat products including oat bran lowered LDL cholesterol by 9.3 mg/dL (0.24 mmol/L), with moderate certainty. — patients with dyslipidemia in RCTs of oat-based products (oat beta-glucan, oat bran, wholegrain oat) for at least 4 weeks (n = 17 trials, 1731 subjects) Evidence A source
  LDL-C WMD -9.3 mg/dL (95% CI -13 to -5.8; metric: -0.24 mmol/L, -0.33 to -0.15), TC -12 mg/dL (-19 to -6.6; metric: -0.32 mmol/L, -0.48 to -0.17), moderate certainty (GRADE); little effect on HDL-C and TG
• A 1992 meta-analysis of 10 controlled oat trials found a 0.13 mmol/L fall in total cholesterol, larger in people starting at 228 mg/dL (5.9 mmol/L) or more and eating 3 g or more of soluble fiber a day. — randomized controlled trials of oat products (oat bran and oatmeal) with diet and body weight assessment, to March 1991 (n = 20 trials identified, 10 pooled) Evidence A source
  Total cholesterol -0.13 mmol/L (-5.9 mg/dL), 95% CI -7.3 to -0.66 mg/dL (-0.19 to -0.017 mmol/L); larger with baseline >= 228 mg/dL (5.9 mmol/L) and >= 3 g soluble fiber
• In a blinded crossover trial of free-living adults with raised LDL on a step I diet, 0.99 oz (28 g) of oat bran twice a day lowered LDL by 3.9% while wheat cereal and diet alone saw LDL rise. — men and women aged 20 to 70 with baseline LDL in the 50th to 95th percentile, AHA step I diet plus oat bran 28 g twice daily vs wheat cereal (n = 145 completers (82% of randomized)) Evidence B source
  LDL-C -3.9% (oat bran) vs +4.0% (wheat cereal) vs +6.4% (diet alone); total cholesterol -2.2% vs +3.3% vs +6.0%
• EU law says most people with gluten intolerance can eat oats without harm, but oats are often contaminated with wheat, rye or barley during harvest, transport, storage and processing. Oats in a food labeled gluten-free must be specially produced and contain no more than 20 mg of gluten per kg. — people with gluten intolerance buying foods sold in the EU Evidence E source
  Most people with gluten intolerance tolerate oats; contamination with wheat, rye or barley is the main concern; oats in a gluten-free food must be specially produced and hold no more than 20 mg/kg gluten
• A meta-analysis of 28 studies in celiac disease found that pure, uncontaminated oats eaten for 12 months did not affect symptoms (SMD -0.22, 95% CI -0.56 to 0.13), with no difference between adults and children. — patients with celiac disease on a gluten-free diet, 6 RCTs and 2 non-randomized trials with 661 patients plus observational studies (n = 28 studies) Evidence A source
  Symptom score SMD -0.22 (95% CI -0.56 to 0.13) at 12 months with pure oats; no difference between adults and children
• A 1990 report in a geriatrics journal links oat bran bezoars causing obstruction with people who had no dentures. — older people without dentures, J Am Geriatr Soc letter Evidence D source
  Oat bran bezoars causing intestinal obstruction in people without dentures
• In 28 randomized trials, 3 g or more of oat beta-glucan a day cut LDL cholesterol by 9.7 mg/dL (0.25 mmol/L) and total cholesterol by 12 mg/dL (0.30 mmol/L) without changing HDL or triglycerides, with a larger drop in people with higher baseline LDL or diabetes. — adults in 28 RCTs comparing at least 3 g/d oat beta-glucan with control, 2-12 weeks, doses 3.0-12.4 g/d (n = 28 RCTs) Evidence A source
  LDL -9.7 mg/dL (95% CI 7.7 to 12; metric: -0.25 mmol/L, 0.20 to 0.30), TC -0.30 (0.24-0.35); HDL and TG unchanged; no dose or duration effect
• 1.1 oz (30 g) of oat bran a day (8.9 g fiber) for 3 months on top of dietary advice lowered office systolic and diastolic blood pressure and reduced antihypertensive drug use in 50 patients with essential hypertension. — 50 patients with essential hypertension, China, 25 per arm, 3 months (n = 50) Evidence B source
  Office SBP lower (P < 0.001), DBP lower (P < 0.028), 24 h ambulatory changes greater, antihypertensive use reduced (P = 0.021)
• In 112 women with diet-treated gestational diabetes, 1.1 oz (30 g) of oat bran a day at lunch and dinner for 4 weeks lowered fasting and 2-hour post-meal glucose versus diet alone (P < 0.001). — 112 pregnant women with gestational diabetes treated with diet, Iran, 56 per arm, 4 weeks (n = 112) Evidence B source
  Fasting and 2 h postprandial glucose lower than control at weeks 2 and 4 (P < 0.001); magnitudes not in the abstract

What is still unknown

• A meta-analysis of 67 controlled trials found each gram of soluble fiber from oat bran, psyllium or pectin lowered LDL cholesterol by about 2.2 mg/dL (0.057 mmol/L), so the effect stays small within practical intakes. — controlled trials of pectin, oat bran, guar gum and psyllium, soluble fiber 2-10 g/day (n = 67 trials) Evidence A source
  LDL-C -2.2 mg/dL (-0.057 mmol/L) per g soluble fiber (95% CI -0.070 to -0.044); total cholesterol -1.7 mg/dL (-0.045 mmol/L) per g; oat, psyllium and pectin not different
• In a 6-week double-blind crossover trial of 20 healthy adults with normal cholesterol, 87 g a day of oat bran lowered cholesterol no more than low-fiber refined wheat, and both cut it by 7 to 8%. — healthy subjects aged 23 to 49, isocaloric supplements of high-fiber oat bran (87 g/day) or low-fiber refined wheat, six weeks each (n = 20) Evidence C source
  LDL 104 vs 107 mg/dL (2.69 vs 2.77 mmol/L) (oat bran vs low-fiber wheat), not significant; both lowered baseline total cholesterol by 7-8%, explained by less saturated fat in the diet
• In a single-blind crossover trial of 12 people with high blood lipids already on a lipid-lowering diet, oat bran bread for 4 weeks did not lower LDL cholesterol more than wheat bran bread of similar fiber content. — hyperlipidemic subjects aged 38 to 66 stabilized on lipid-lowering diets for at least three months; oat bran bread vs wheat bran bread, four weeks each (n = 12) Evidence B source
  Cholesterol, triglyceride and LDL-C did not change significantly in either period; both diets lowered serum cholesterol about 4%
• The one RCT of oat bran in gestational diabetes, in 112 women, measured only the mothers' blood glucose. It reported nothing on birth or newborn outcomes, so safety for the baby is untested. — 112 women with gestational diabetes treated with diet (n = 112) Evidence B source
  Outcomes measured were maternal fasting and 2-hour glucose only; no fetal or neonatal outcome reported
• Adding 1.4 oz (40 g) of oat bran a day to a low-calorie diet for 6 weeks gave 154 outpatients no extra remission of metabolic syndrome, and HDL cholesterol fell from 43.6 to 41.2 mg/dL in the oat bran group only. — 154 outpatients with metabolic syndrome, mean age 47.6, Brazil, pragmatic open-label, 6 weeks (n = 154) Evidence B source
  MetS prevalence 63% vs 64.8% (P = 0.226); HDL-C 43.6 to 41.2 mg/dL in oat bran group (P = 0.025), unchanged in control
• In a 2025 meta-analysis of prebiotics for inflammatory bowel disease, oat bran did not prevent clinical relapse in ulcerative colitis, with very low overall certainty of evidence. — patients with ulcerative colitis or Crohn's disease in 17 studies (RCTs and prospective observational) (n = 17 studies) Evidence C source
  Oat bran: no effect on relapse in UC; germinated barley foodstuff RR 0.40 (0.15-1.03); FOS kestose RR 2.75 for remission

The bottom line

Form matters about as much as dose. The same 5 to 6 g a day of beta-glucan from oat bran lowered LDL by 10 mg/dL (0.26 mmol/L) (6.7 percent) when it was drunk in orange juice. Baked into bread and cookies, the same amount moved LDL by 4.6 mg/dL (0.12 mmol/L), which did not reach significance. That was 48 mildly hypercholesterolemic adults in the baking study and 25 of them in the juice crossover, small enough that the authors offer processing or the food matrix as an explanation rather than proving one. Portions swell in the pan. A cup of cooked oat bran cereal weighs 8.5 oz (240 g), and one ounce of dry bran yields about 150 g cooked. That is also why the cooked figures per 3.5 oz (100 g) look thin: raw bran holds 1.17 mg thiamin and cooked bran 0.16 mg, which is dilution by water rather than a measured loss. The trial that pushed hardest used a plateful. Adding 3.6 oz (102 g) of oat bran a day, about 6 g of soluble fiber, to a low-fiber diet for 2 weeks cut total cholesterol by 14 percent against 4 percent on control in 24 young adults. Fecal energy loss rose by 37 percent in the same two weeks. That dose sits far above ordinary eating, and the trial ran a fortnight. On blood sugar the effect is immediate and modest per gram. In 40 healthy adults, each gram of oat beta-glucan added to instant oatmeal cut the 2-hour glucose area by 7 percent and the peak rise by 15 percent, measured from single meals with no longer outcome followed. A pilot in 10 healthy adults who drank oat bran in water before white bread got about 4.35 percent less glucose area per gram of beta-glucan, using a commercial concentrate. Over months the picture holds for the food and not for the extract. In 18 randomized trials with 1,024 people who had type 2 diabetes, high cholesterol or overweight, whole oats and oat bran at 20 to 136 g a day lowered HbA1c, fasting glucose and fasting insulin, while beta-glucan extracts alone did not. That abstract reports P values without effect sizes, so how big those falls were is not something we can tell you. The regulators sit in the same place. The EU authorizes the wording that oat beta-glucan lowers blood cholesterol and authorizes a post-meal glucose claim at 4 g of beta-glucan per 30 g of available carbohydrate, while a branded oat bran claim about maintaining healthy blood glucose is listed as non-authorized. Those are rulings on whether the evidence was sufficient at assessment. They are not effect sizes, and non-authorized is not the same as disproven. The side effects on record are the ones you would guess. In 17 randomized trials with 1,731 people with dyslipidemia, oat products including oat bran lowered LDL by 9.3 mg/dL (0.24 mmol/L) against placebo or usual diet, and the adverse effects reported were gastrointestinal: diarrhea, nausea and flatulence. Most of those trials carried a high risk of bias or concerns about it. Blood pressure has one small trial. In 50 people with essential hypertension in China, 1.1 oz (30 g) of oat bran a day for 3 months on top of dietary advice lowered office systolic and diastolic pressure and reduced the use of antihypertensive drugs. It was a single-center study that does not publish the size of those changes. If you take medicine for blood pressure, that belongs in a conversation with whoever prescribes it. Pregnancy has one trial as well, filed under who this works differently for. In 112 Iranian women with diet-treated gestational diabetes, 1.1 oz (30 g) of oat bran a day at lunch and dinner for 4 weeks left fasting and 2-hour post-meal glucose lower than diet alone (P < 0.001). That was one unblinded trial in one country, and it leaves the magnitudes out. It measured only the mothers' blood glucose and reported nothing on birth or newborn outcomes, so safety for the baby is untested. Zinc is the old worry about bran, and the one measurement does not back it. Oat bran at 142 g a day for 21 days left fractional zinc absorption at 0.40 against 0.48 without it (P = 0.07) in 12 adults, and the bran carried enough zinc of its own that more was absorbed in total, 99 against 64 umol. That study had 12 people and an animal-protein background diet, where phytate binds less than it would on a plant-based one. Large amounts carry one rare but serious risk. A 1989 case report describes small-bowel obstruction caused by a bezoar, a solid mass, of oat bran, and a 1990 letter in a geriatrics journal ties oat bran bezoars causing obstruction to people who had no dentures. Both records are titles without abstracts, so the amounts eaten are unknown to us, and they show the event exists, not how often it happens. No card on this page sets any upper limit for oat bran, and we found no agency ceiling for dietary fiber, so the 102 and 142 g daily doses in the trials above stand here without one. Celiac disease is the second caution. EU law says most people with gluten intolerance can eat oats without harm, but oats are often contaminated with wheat, rye or barley during harvest, transport, storage and processing. Oats in a food labeled gluten-free must be specially produced and contain no more than 20 mg of gluten per kg. A meta-analysis of 40 food testing studies found oats the most contaminated food. Pure, uncontaminated oats eaten for 12 months did not affect symptoms in a meta-analysis of people with celiac disease, on low-quality evidence, and ordinary oat bran is not that product unless it is sold as gluten-free. Medicines are the third. The FDA-approved levothyroxine label says dietary fiber may bind the drug and lower its absorption from the gut, and in a case series of hypothyroid patients who needed unusually high doses, stopping a fiber supplement lowered the dose they needed. Neither names oat bran. Beyond that and the blood pressure trial we have no card on oat bran with medicines, none on children outside celiac disease and none on oat allergy. Two results push back, and they belong here. Adding 1.4 oz (40 g) of oat bran a day to a low-calorie diet for 6 weeks gave 154 Brazilian outpatients with metabolic syndrome no extra remission, 63 percent against 64.8 percent. HDL cholesterol fell in that group from 43.6 to 41.2 mg/dL, a change within the group whose difference from the control group was not significant (P = 0.078), in an open-label trial. In a 2025 review of prebiotics for inflammatory bowel disease, oat bran did not prevent clinical relapse in ulcerative colitis, on very low certainty and few studies. One housekeeping note. USDA has no retention factor for oat bran and no UK reference record exists for it, so the cooked composition on this page cannot be cross-checked against a second source.

Sources

1. oatb-c4-15 · regulation
   Oat bran is produced by grinding clean oat groats or rolled oats and separating the resulting oat flour by suitable means into fractions such that the oat bran fraction is not more than 50 percent of the original starting material and provides at least 5.5 percent (dry weight basis (dwb)) β-glucan soluble fiber and a total dietary fiber content of 16 percent (dwb), and such that at least one-third of the total dietary fiber is soluble fiber
   21 CFR 101.81, Health claims: Soluble fiber from certain foods and risk of coronary heart disease (CHD) · checked 2026-09-23
2. oatb-c4-22 · reference dataset
   Oat bran, raw FDC 168872 | Thiamin 1.17 mg | Selenium 45.2 ug | Phosphorus 734 mg || Oat bran, cooked | Thiamin 0.16 mg | Selenium 7.7 ug | Phosphorus 119 mg || USDA R6: no oat bran row; selenium not in R6
   USDA FoodData Central, SR Legacy, FDC 168872 (Oat bran, raw); USDA Table of Nutrient Retention Factors, Release 6 (2007) · checked 2026-09-23
3. oatb-c4-06 · RCT crossover
   A double-blind, randomized crossover study in 24 adults (age 25.2±2.7 years; body mass index: 24.9±2.9 kg/m2), who completed two 2-week dietary intervention periods: low-fiber diet (control) or an oat bran (control +102 g oat bran/day) diet...Total cholesterol decreased by 14% during the oat bran period compared with 4% during the control period (P<0.001)...energy excretion was increased by 37% (1014 vs 638 kJ/day, P<0.001)
   Eur J Clin Nutr, 2011 · checked 2026-09-23
4. oatb-c4-11 · RCT crossover
   Each gram of OBG reduced iAUC by 7% and peak-rise by 15%. Thus, to achieve a ≥20% reduction in iAUC relative to CR, 1.6 g OBG had to be added to IO (74 ± 7 vs. 93 ± 6 mmol min L-1, p < 0.05), but, to achieve a 20% reduction in peak-rise, only 0.4 g OBG was required (2.00 ± 0.1 vs. 2.40 ± 0.1 mmol, p < 0.05).
   Food Funct, 2018 · checked 2026-09-23
5. oatb-c4-16 · regulation
   the whole oat or barley foods shall contain at least 0.75 gram (g) of soluble fiber per reference amount customarily consumed of the food product
   21 CFR 101.81, Health claims: Soluble fiber from certain foods and risk of coronary heart disease (CHD) · checked 2026-09-23
6. oatb-c4-20 · regulation
   at least 1 g of beta-glucans from oats, oat bran, barley, barley bran, or from mixtures of these sources per quantified portion...the beneficial effect is obtained with a daily intake of 3 g of beta-glucans from oats, oat bran, barley, barley bran, or from mixtures of these beta-glucans...at least 4 g of beta-glucans from oats or barley for each 30 g of available carbohydrates in a quantified portion as part of the meal
   Regulation (EU) No 432/2012, consolidated text 2016-01-01, EUR-Lex · checked 2026-09-23
7. oatb-c4-21 · reference dataset
   Oat bran cereal, cooked | 1 cup, cooked 240 g | 1 cup, dry, yields 500 g | 1 oz, dry, yields 150 g | Quantity not specified 240 g
   USDA FNDDS (Food and Nutrient Database for Dietary Studies), fdc_id 2708444 · checked 2026-09-23
8. ev-obc-11 · controlled trial
   In conclusion, the absorption of zinc was high and not affected by addition of oat bran.
   J Nutr, 2000 · checked 2026-10-07
9. oatb-c4-12 · controlled clinical trial
   The effect of a mean daily intake of 142 g of oat bran (102 g/10 MJ) on absorption of zinc was evaluated by the use of stable isotopes and fecal monitoring in 12 healthy subjects (6 males and 6 females)...The fractional absorptions (means +/- SD) of zinc from the low-fiber and oat bran diets were 0.48 +/- 0.11 and 0.40 +/- 0.15 (P = 0.07), respectively. The higher zinc content in the oat bran period resulted in a greater amount of zinc absorbed (64 +/- 19 micromol and 99 +/- 51 micromol, respectively, P = 0.009).
   J Nutr, 2000 · checked 2026-09-23
10. oatb-c4-13 · RCT crossover
    Linear regression analysis showed that each gram of oat β-glucan reduced glucose AUC by 4.35% ± 1.20% (r = 0.507, p = 0.0008, n = 40) and peak rise by 6.57% ± 1.49% (r = 0.582, p < 0.0001).
    Nutrients, 2016 · checked 2026-09-23
11. oatb-c4-10 · RCT
    In study 1, the change in LDL cholesterol did not differ significantly (-0.12 mmol/L; P = 0.173) between the 2 groups. In study 2, the drink rich in beta-glucan decreased LDL cholesterol by 0.26 +/- 0.07 mmol/L (6.7 +/- 1.8%; P = 0.001) and the ratio of total to HDL cholesterol by 0.26 +/- 0.11 (5.4 +/- 2.1%; P = 0.029) compared with the other drink...The food matrix or the food processing, or both, could have adverse effects on the hypocholesterolemic properties of oat beta-glucan.
    Am J Clin Nutr, 2003 · checked 2026-09-23
12. ev-obc-01 · network meta-analysis
    Cumulative ranking analyses showed that oat bran was the most effective intervention strategy for TC and LDL-C improvements, with significant decreases of - 0.35 mmol/L (95% CI - 0.47, - 0.23 mmol/L) and - 0.32 mmol/L (95% CI - 0.44, - 0.19 mmol/L) in TC and LDL-C compared with control, respectively.
    Eur J Nutr, 2019 · checked 2026-10-07
13. ev-obc-05 · RCT
    Fifty-six grams of oat bran resulted in significantly greater reductions in LDL-C levels than 56 g of oatmeal.
    JAMA, 1991 · checked 2026-10-07
14. ev-obc-06 · RCT
    After 21 d, OB significantly decreased total cholesterol by 12.8% (P less than 0.001), low-density-lipoprotein cholesterol by 12.1% (P less than 0.004), and apolipoprotein B-100 by 13.7% (P less than 0.001) whereas WB had no significant effect.
    Am J Clin Nutr, 1991 · checked 2026-10-07
15. oatb-c4-01 · meta-analysis of RCTs
    In total, fifty-eight trials (n 3974) were included. A median dose of 3·5 g/d of oat β-glucan significantly lowered LDL-cholesterol (-0·19; 95 % CI -0·23, -0·14 mmol/l, P<0·00001), non-HDL-cholesterol (-0·20; 95 % CI -0·26, -0·15 mmol/l, P<0·00001) and apoB (-0·03; 95 % CI -0·05, -0·02 g/l, P<0·0001) compared with control interventions.
    Br J Nutr, 2016 · checked 2026-09-23
16. ev-obc-10 · meta-analysis
    Oat-related adverse events were mostly gastrointestinal such as diarrhea, nausea, and flatulence being the most prevalent.
    Food Funct, 2024 · checked 2026-10-07
17. hf2-oatb-3 · meta-analysis of surveys
    the overall prevalence of gluten contamination was estimated at 15.12% (95% CI: 9.56%-21.70%), with more than 20 mg/kg of gluten...Moreover, it was noticed that oats were the most contaminated food.
    Br J Nutr, 2022 · checked 2026-10-08
18. hf2-oatb-4 · case report
    Small-bowel obstruction caused by oat-bran bezoar.
    N Engl J Med, 1989 · checked 2026-10-08
19. hf2-oatb-6 · FDA drug label section
    Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the gastrointestinal tract.
    Levothyroxine sodium, FDA-approved label, drug-food interactions, effective 2026-03-24 · checked 2026-10-08
20. hf2-oatb-7 · case series
    T4 requirements, reflected by either decreased serum TSH or by decreased T4 dose, was observed in conjunction with decreased dietary fiber intake compared with T4 requirement during increased dietary fiber intake. In vitro experiments carried out to determine the mechanism of interaction between dietary fiber and T4 revealed dose dependent, nonspecific adsorption of levothyroxine by wheat bran.
    J Clin Endocrinol Metab, 1996 · checked 2026-10-08
21. oatb-c4-04 · meta-analysis of RCTs
    We finally included 17 eligible trials with 1731 subjects...Pooled estimates showed that oat-based products may result in a large reduction in LDL-C (WMD, -0.24 mmol L-1; 95% CI: -0.33, -0.15) (moderate certainty) and TC (WMD, -0.32 mmol L-1; 95% CI: -0.48, -0.17) (moderate certainty)...Oat-related adverse events were mostly gastrointestinal such as diarrhea, nausea, and flatulence being the most prevalent.
    Food Funct, 2024 · checked 2026-09-23
22. ev-obc-12 · regulation
    ( 1 ) 3 g or more per day of β-glucan soluble fiber from either whole oats or barley, or a combination of whole oats and barley.
    21 CFR 101.81, Health claims: Soluble fiber from certain foods and risk of coronary heart disease (CHD) · checked 2026-10-07
23. ev-obc-13 · regulatory register
    POL-HC-6248 Oat beta-glucan Oat beta-glucan has been shown to lower/reduce blood cholesterol. High cholesterol is a risk factor in the development of coronary heart disease -/- Authorised
    EU Register on nutrition and health claims, claim POL-HC-6248, snapshot 2026-09-21 · checked 2026-10-07
24. oatb-c4-03 · network meta-analysis of RCTs
    Fifty-five eligible trials with a total of 3900 participants were included. Cumulative ranking analyses showed that oat bran was the most effective intervention strategy for TC and LDL-C improvements, with significant decreases of - 0.35 mmol/L (95% CI - 0.47, - 0.23 mmol/L) and - 0.32 mmol/L (95% CI - 0.44, - 0.19 mmol/L) in TC and LDL-C compared with control, respectively...Barley, brown rice, wheat and wheat bran were shown to be ineffective in improving blood lipid compared with control.
    Eur J Nutr, 2019 · checked 2026-09-23
25. oatb-c4-05 · meta-analysis of RCTs
    relevant data were extracted from 18 studies (n = 1024). Oat product dose ranged from 20 g d(-1) to 136 g d(-1), and beta-glucan extract dose ranged from 3 g d(-1) to 10 g d(-1). Compared with the control, oat intake resulted in a greater decrease in fasting glucose and insulin of subjects (P < 0.05), but beta-glucan extract intake did not.
    Food Funct, 2016 · checked 2026-09-23
26. oatb-c4-17 · regulatory register
    POL-HC-6248 Oat beta-glucan Oat beta-glucan has been shown to lower/reduce blood cholesterol. High cholesterol is a risk factor in the development of coronary heart disease -/- Authorised
    EU Register on nutrition and health claims, claim POL-HC-6248, snapshot 2026-09-21 · checked 2026-09-23
27. oatb-c4-18 · regulatory register
    POL-HC-6331 Beta-glucans from oats and barley Consumption of beta-glucans from oats or barley as part of a meal contributes to the reduction of the blood glucose rise after that meal Authorised
    EU Register on nutrition and health claims, claim POL-HC-6331, snapshot 2026-09-21 · checked 2026-09-23
28. oatb-c4-19 · regulatory register
    POL-HC-6856 CalorieControl Trim® Oat Bran The inclusion of 3 grams oat beta glucan soluble fiber per day from Calorie ControlTrim® Oat Bran, as part of a diet low in saturated fat and a healthy lifestyle, can help maintain healthy blood glucose levels. Oat beta glucan soluble fiber from Calorie ControlTrim® Oat Bran, as part of a diet low in saturated fat and a healthy lifestyle, can help maintain healthy blood glucose levels. Calorie ControlTrim® Oat Bran helps maintain healthy blood glucose levels. Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-6856, snapshot 2026-09-21 · checked 2026-09-23
29. ev-obc-02 · meta-analysis
    Pooled estimates showed that oat-based products may result in a large reduction in LDL-C (WMD, -0.24 mmol L-1; 95% CI: -0.33, -0.15) (moderate certainty) and TC (WMD, -0.32 mmol L-1; 95% CI: -0.48, -0.17) (moderate certainty).
    Food Funct, 2024 · checked 2026-10-07
30. ev-obc-04 · meta-analysis
    Larger reductions were seen in trials in which subjects had initially higher blood cholesterol levels (greater than or equal to 5.9 mmol/L [greater than or equal to 229 mg/dL]), particularly when a dose of 3 g or more of soluble fiber was employed.
    JAMA, 1992 · checked 2026-10-07
31. ev-obc-07 · RCT
    Blood lipid studies demonstrated significantly greater reductions in total cholesterol (average -2.2%) and LDL cholesterol (average -3.9%) in the oat-bran groups than in the wheat-cereal groups (average total cholesterol +3.3%, average LDL cholesterol +4.0%) or in the diet alone group (total cholesterol +6.0%; LDL cholesterol +6.4%).
    J Fam Pract, 1991 · checked 2026-10-07
32. hf2-oatb-1 · EU regulation
    Most people with intolerance to gluten can include oats in their diet without adverse effect on their health. This is an issue of ongoing study and investigation by the scientific community. However, a major concern is the contamination of oats with wheat, rye or barley that can occur during grain harvesting, transport, storage and processing. ... Oats contained in a food presented as gluten-free or very low gluten must have been specially produced, prepared and/or processed in a way to avoid contamination by wheat, rye, barley, or their crossbred varieties and the gluten content of such oats cannot exceed 20 mg/kg.
    Commission Implementing Regulation (EU) No 828/2014 of 30 July 2014 on the requirements for the provision of information to consumers on the absence or reduced presence of gluten in food, OJ L 228/5 · checked 2026-10-08
33. hf2-oatb-2 · meta-analysis
    All randomized controlled trials used pure/uncontaminated oats. Oat consumption for 12 months did not affect symptoms (standardized mean difference: reduction in symptom scores in patients who did and did not consume oats, -0.22; 95% CI, -0.56 to 0.13; P = .22)... Subgroup analyses of adults vs children did not reveal differences. The overall quality of evidence was low.
    Gastroenterology, 2017 · checked 2026-10-08
34. hf2-oatb-5 · case report
    Dentureless distention: oat bran bezoars cause obstruction.
    J Am Geriatr Soc, 1990 · checked 2026-10-08
35. oatb-c4-02 · meta-analysis of RCTs
    OBG in doses of ≥3 g/d reduced low-density lipoprotein (LDL) and total cholesterol relative to control by 0.25 mmol/L (95% CI: 0.20, 0.30; P < 0.0001) and 0.30 mmol/L (95% CI: 0.24, 0.35; P < 0.0001), respectively...There was a significantly greater effect for both LDL and total cholesterol in subjects with diabetes compared with those without (although based on few studies).
    Am J Clin Nutr, 2014 · checked 2026-09-23
36. oatb-c4-07 · RCT
    In addition to dietary guidance, one bag of oat bran (30 g/d) supplement (containing DF 8.9 g) was delivered to the DF group...After intervention, the office systolic blood pressure (oSBP; P < 0.001) and office diastolic blood pressure (oDBP; P < 0.028) in the DF group were lower than those in the control group...The use of antihypertensive drugs in the DF group was significantly reduced (P = 0.021).
    Nutr Metab Cardiovasc Dis, 2021 · checked 2026-09-23
37. oatb-c4-08 · RCT
    In addition to the diet, the intervention group received 30 g of oat bran daily for 4 weeks at lunch and dinner...2 and 4 weeks after the intervention, mean fasting blood glucose and two-hour postprandial (2hpp) glucose decreased significantly in the intervention group compared with the control group (P < 0.001).
    BMC Endocr Disord, 2021 · checked 2026-09-23
38. ev-obc-03 · meta-analysis
    Soluble fiber, 2-10 g/d, was associated with small but significant decreases in total cholesterol [-0.045 mmol L(-1).g soluble fiber(-1) (95% CI: -0.054, -0.035)] and LDL cholesterol [-0.057 mmol.L(-1).g(-1) (95% CI: -0.070, -0.044)].
    Am J Clin Nutr, 1999 · checked 2026-10-07
39. ev-obc-08 · controlled trial
    Those changes in dietary fats were sufficient to explain all of the reduction in serum cholesterol levels caused by the high-fiber and low-fiber diets.
    N Engl J Med, 1990 · checked 2026-10-07
40. ev-obc-09 · RCT
    We conclude that this oat bran bread consumed as part of a lipid-correcting diet did not influence lipoproteins to any greater extent than wheat bread of similar total fibre content.
    Aust N Z J Med, 1991 · checked 2026-10-07
41. hf2-oatb-8 · randomized controlled trial
    In addition to the diet, the intervention group received 30 g of oat bran daily for 4 weeks at lunch and dinner. Tests of fasting blood glucose and two-hour postprandial (2hpp) glucose were taken from both groups: before the intervention, and 2 and 4 weeks after the start of the intervention.
    BMC Endocr Disord, 2021 · checked 2026-10-08
42. oatb-c4-09 · RCT
    The intervention group (n = 83) received a low-calorie diet plus 40 g/d of oat bran; the control group (n = 71) received a low-calorie diet only...Mean high-density lipoprotein cholesterol (HDL-C) was reduced in the intervention group (43.6 ± 9.6 to 41.2 ± 9.5 mg/dL; P = 0.025), but not in the control group (44.6 ± 10.5 to 44.5 ± 12.1 mg/dL; P = 0.890).
    Nutrition, 2019 · checked 2026-09-23
43. oatb-c4-14 · meta-analysis of mixed designs
    For maintenance of remission in UC, germinated barley foodstuff trended toward preventing clinical relapse (relative risk, 0.40; 95% confidence interval, 0.15-1.03; n = 59), but OF-IN, oat bran, and Plantago ovata did not...The overall certainty of evidence was very low.
    Inflamm Bowel Dis, 2025 · checked 2026-09-23