Oat bran cereal: a small, measured cut in LDL cholesterol

A meta-analysis of 28 randomized trials found that at least 3 g of oat beta-glucan a day, taken for 2 to 12 weeks, lowered LDL cholesterol by 9.7 mg/dL (95% CI 7.7 to 12; metric: 0.25 mmol/L, 0.20 to 0.30), with larger drops in people whose LDL was higher or who had diabetes. HDL and triglycerides did not change. The beta-glucan in those trials came from all kinds of oat foods, bran cereal among them. Trials of the cereal itself point the same way. In 152 Hispanic American adults with raised LDL, oat bran cereal giving 3 g beta-glucan a day lowered LDL by 5.3 percent over 6 weeks, while corn cereal did not. In 12 men with high cholesterol on a metabolic ward, a cereal with 25 g oat bran a day cut LDL by 8.5 percent in 2 weeks against corn flakes. The effect depends on the fiber staying thick. When enzymes broke down the viscosity of oat bran in a drink tested on 20 healthy adults, it left the stomach faster and raised blood glucose and insulin more than intact oat bran. Two cautions follow below: 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.

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• Under US rules, oat bran eligible for the heart health claim must supply at least 5.5% beta-glucan and 16% total fiber on a dry basis, with at least one third of the fiber soluble. — — Evidence E source
  Beta-glucan >= 5.5% dwb; total dietary fiber >= 16% dwb; soluble >= 1/3 of fiber

What a real portion looks like

• A cooked 1-cup (240 g) serving of oat bran cereal gives about 110 calories, 7.0 g fiber and 7.7 g protein, and a ready-to-eat single serving weighs 1.1 oz (30 g). — — Evidence E source
  Cooked per 3.5 oz (100 g): 46 calories, 2.9 g fiber, 3.21 g protein, 69 mg Na, 0.95 mg Fe; per 240 g cup: 110.4 calories, 7.0 g, 7.7 g, 165.6 mg, 2.3 mg

What your body absorbs

• In a crossover RCT in 20 adults, oat bran whose viscosity was broken down by enzyme treatment emptied from the stomach faster and raised blood glucose and insulin more than intact viscous oat bran. — 20 healthy normal-weight adults, two 10 fl oz (300 mL) oat bran drinks with 10.2 g fiber (n = 20) Evidence B source
  Low viscosity: higher glucose (P < 0.001) and insulin (P = 0.008), faster gastric emptying (P = 0.034)
• In a crossover RCT in 40 adults, each extra gram of oat-bran beta-glucan added to instant oatmeal cut the 2-hour glucose response by 7% and the glucose peak by 15%. — 40 adults, single breakfasts of instant oatmeal with 0-1.6 g added oat beta-glucan (n = 40) Evidence B source
  -7% iAUC and -15% peak rise per g beta-glucan; 1.6 g needed for a 20% iAUC reduction

What cooking and storage change

• Baking oat-bran beta-glucan into bread and cookies (5.9 g a day for 4 weeks) did not significantly lower LDL, while the same fiber in orange juice cut LDL by 10 mg/dL (0.26 mmol/L) (6.7%) in 2 weeks. — 48 mildly hypercholesterolemic adults (bread/cookies); 25 in a crossover drink study (n = 48) Evidence B source
  Bread/cookies: LDL -4.6 mg/dL (-0.12 mmol/L), P = 0.173; drink: LDL -10 mg/dL (-0.26 mmol/L), P = 0.001

What it does to your health

• In an RCT in 152 Hispanic American adults with raised LDL, oat bran cereal providing 3 g beta-glucan a day for 6 weeks lowered LDL cholesterol by 5.3%, while corn cereal did not. — 152 Hispanic American men and women aged 30-70, LDL-C 120-190 mg/dL, 6 weeks (n = 152) Evidence B source
  LDL-C -9.4 mg/dL (-5.3%) vs +1.2 mg/dL with corn cereal; P = .0007
• In a metabolic-ward crossover RCT in 12 men with high cholesterol, a ready-to-eat oat bran cereal with 25 g oat bran a day lowered LDL cholesterol by 8.5% in 2 weeks versus corn flakes. — 12 hypercholesterolemic men on a metabolic ward, 2-week periods (n = 12) Evidence B source
  TC -5.4%, LDL-C -8.5% vs corn flakes
• A meta-analysis of 28 RCTs found that at least 3 g of oat beta-glucan a day lowered LDL cholesterol by 9.7 mg/dL (0.25 mmol/L), with larger drops in people with higher LDL or diabetes. — adults in 28 RCTs, 3.0-12.4 g/day oat beta-glucan for 2-12 weeks (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 mmol/L (95% CI 0.24-0.35); no HDL or TG change
• In an RCT in 50 people with hypertension, 1.1 oz (30 g) of oat bran a day (8.9 g fiber) for 3 months lowered office and 24-hour blood pressure and reduced antihypertensive drug use versus diet advice alone. — 50 adults with essential hypertension in China, 3 months (n = 50) Evidence B source
  Office SBP lower (P < 0.001), DBP lower (P < 0.028); drug use reduced (P = 0.021); mmHg not in abstract

Safety, limits and interactions

• 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 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
• 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
• 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

What people believe that the data does not support

• In a 6-week RCT in 154 adults with metabolic syndrome on a low-calorie diet, adding 1.4 oz (40 g) of oat bran a day gave no extra benefit and HDL fell from 43.6 to 41.2 mg/dL. — 154 outpatients with metabolic syndrome, mean age 47.6, low-calorie diet for 6 weeks (n = 154) Evidence B source
  No between-group difference in MetS remission; HDL-C 43.6 to 41.2 mg/dL in oat bran group

Who this works differently for

• In an RCT in 112 women with diet-treated gestational diabetes, adding 1.1 oz (30 g) of oat bran a day for 4 weeks lowered fasting and 2-hour post-meal glucose versus diet alone. — 112 pregnant women with gestational diabetes in Iran, 4 weeks (n = 112) Evidence B source
  Fasting and 2-h glucose lower at 2 and 4 weeks (P < 0.001); size not in abstract

What is still unknown

• 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

The bottom line

A cooked cup of oat bran cereal, 240 g, gives about 110 calories, 7.0 g fiber and 7.7 g protein, recalculated from US survey values per 3.5 oz (100 g). A ready-to-eat single serving weighs 1.1 oz (30 g), and the US tables hold no nutrient values for it. To carry the US heart health claim, oat bran must contain at least 5.5 percent beta-glucan and 16 percent total fiber on a dry basis. That is a label definition and says nothing about what a given box averages. Processing matters. When 48 adults with mildly raised cholesterol ate 5.9 g of oat-bran beta-glucan a day baked into bread and cookies for 4 weeks, LDL fell by 4.6 mg/dL (0.12 mmol/L), a change that did not reach significance. The same fiber in orange juice cut LDL by 10 mg/dL (0.26 mmol/L) in 2 weeks in a separate group of 25. The authors suspect baking or the food matrix degraded the beta-glucan. For blood sugar, each extra gram of oat-bran beta-glucan added to instant oatmeal cut the 2-hour glucose response by 7 percent in 40 adults, measured after single breakfasts. Two trials in patients looked promising and are small. In 112 women with gestational diabetes in Iran, 1.1 oz (30 g) of oat bran a day for 4 weeks lowered fasting and 2-hour glucose against diet alone. It was open-label, reported no outcomes for the babies and gave no effect size in its abstract, so safety for the baby is untested. In 50 people with hypertension in China, 30 g a day for 3 months lowered office blood pressure, and the oat bran group used fewer blood pressure drugs. The abstract gives no figures in mmHg and does not say how those drug changes were decided, so it is no guide to changing medication. On a diet that is already doing the work, extra oat bran added little. In 154 adults with metabolic syndrome on a low-calorie diet, adding 40 g a day for 6 weeks gave no extra benefit, and the fall in HDL from 43.6 to 41.2 mg/dL in that group did not reach significance against control (P = 0.078). Three cautions apply to oat bran in general, not to any tested box of cereal. Gluten comes first. 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 an oat bran cereal is not that product unless it is sold as gluten-free. Large amounts are the second. 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 to people who had no dentures. Both are titles without abstracts, so the amounts are unknown to us, and they show the event exists, not how often it happens. We found no agency upper limit for dietary fiber. 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. We have no card on other drug interactions, on children outside celiac disease or on oat allergy. That is a gap in what we checked, not evidence that it is safe for everyone.

Sources

1. obce-r4-10 · regulatory definition
   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 · checked 2026-09-30
2. obce-r4-11 · food portion data
   FNDDS 56208500 Oat bran cereal, cooked (fdc 2708444) | 1 cup, cooked | 240 g ; 1 oz, dry, yields | 150 g ; Energy 46 KCAL per 100 g ; Fiber, total dietary 2.9 G per 100 g ; Protein 3.21 G per 100 g ; Sodium, Na 69 MG per 100 g ; Iron, Fe 0.95 MG per 100 g || FNDDS 57602500 Cereal, oat bran, ready-to-eat (fdc 2708490) | 1 cup | 80 g ; 1 prepackaged single serving | 30 g
   FNDDS 2021-2023, USDA, codes 56208500 and 57602500 · checked 2026-09-30
3. obce-r4-05 · randomized crossover trial
   The oat bran beverage with low viscosity induced a greater postprandial increase in satiety (P = 0.048) and plasma glucose (P < 0.001), insulin (P = 0.008), cholecystokinin (P = 0.035), glucagon-like peptide 1 (P = 0.037), and peptide YY (P = 0.051) and a greater decrease in postprandial ghrelin (P = 0.009) than the beverage with high-viscosity oat bran. Gastric emptying as measured by paracetamol absorption was also faster (P = 0.034) after low-viscosity oat bran beverage consumption.
   J Nutr, 2009 · checked 2026-09-30
4. obce-r4-06 · randomized crossover trial
   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 2026-09-30
5. obce-r4-04 · randomized controlled trial
   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.
   Am J Clin Nutr, 2003 · checked 2026-09-30
6. obce-r4-01 · randomized controlled trial
   The daily dose of beta glucan was 3 g. Consumption of oat cereal was associated with a reduction in plasma levels of both total cholesterol (-10.9+/-21.6 mg/dL; -4.5%) and LDL-C (-9.4+/-20.3 mg/dL; -5.3%). Consumption of corn cereal did not affect either total cholesterol (+1.2+/-18.3 mg/dL; 1.1%) or LDL-C (+1.2+/-17.5 mg/dL; 2.2%).
   J Am Diet Assoc, 2005 · checked 2026-09-30
7. obce-r4-02 · randomized crossover trial
   The oat-bran cereal provided 25 g oat bran/d. The oat-bran cereal diet compared with the corn flakes diet lowered serum total-cholesterol and serum LDL-cholesterol concentrations significantly by 5.4% (p less than 0.05) and 8.5% (p less than 0.025), respectively.
   Am J Clin Nutr, 1990 · checked 2026-09-30
8. obce-r4-03 · 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, with some indication of heterogeneity (P = 0.13 and P = 0.067).
   Am J Clin Nutr, 2014 · checked 2026-09-30
9. obce-r4-08 · randomized controlled trial
   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.
   Nutr Metab Cardiovasc Dis, 2021 · checked 2026-09-30
10. hf2-obce-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
11. hf2-obce-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
12. hf2-obce-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
13. hf2-obce-4 · case report
    Small-bowel obstruction caused by oat-bran bezoar.
    N Engl J Med, 1989 · checked 2026-10-08
14. hf2-obce-5 · case report
    Dentureless distention: oat bran bezoars cause obstruction.
    J Am Geriatr Soc, 1990 · checked 2026-10-08
15. hf2-obce-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
16. hf2-obce-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
17. obce-r4-09 · randomized controlled trial
    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). There was no significant difference in any of the variables between the groups, although the P-value for HDL-C was almost significant (P = 0.078).
    Nutrition, 2019 · checked 2026-09-30
18. obce-r4-07 · 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. ... There was no statistically significant difference between the two groups in terms of mean blood glucose before the intervention, while 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 2026-09-30
19. hf2-obce-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