Corn bran: almost pure fiber, tested mostly in small trials

The largest trial with corn bran in it used a mix. In 169 adults with mild to moderate high cholesterol, 20 g a day of a supplement of guar gum, pectin, soy fiber, pea fiber and corn bran lowered LDL cholesterol by 12.1% over 15 weeks, against 1.3% on placebo. It did not lower iron, ferritin or vitamins A and E. The trial did not separate how much of that came from the corn bran. On its own, crude corn bran is close to pure fiber. USDA lists 79 g per 3.5 oz (100 g) with 224 calories, from a single record with no spread across samples. A cup weighs 2.7 oz (76 g) and would hold about 60 g of fiber. The trials below used between 10 and 52 g a day, which is what studies tested, not a safe range: we have no card on an upper limit or on how much fluid to drink with it. In 10 constipated but otherwise healthy women, 20 g a day of corn bran relieved symptoms better than wheat bran did, and the two brans together raised stool weight by 157%.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• Crude corn bran holds 79 g dietary fiber per 3.5 oz (100 g), with 224 calories, 8.36 g protein and 0.92 g fat. — USDA SR Legacy record for Corn bran, crude Evidence E source
  Fiber 79 g; energy 224 calories; protein 8.36 g; iron 2.79 mg; magnesium 64 mg; selenium 16.5 ug; lutein + zeaxanthin 1355 ug per 3.5 oz (100 g)

What a real portion looks like

• One cup of crude corn bran weighs 2.7 oz (76 g), which works out to about 60 g of dietary fiber. — USDA SR Legacy portion weight for Corn bran, crude Evidence E source
  1 cup = 76 g; about 60 g fiber and 170 calories per cup (computed from per 3.5 oz (100 g) values)

What your body absorbs

• In an RCT of 169 adults, 20 g a day of a fiber mix containing corn bran cut LDL cholesterol by 12.1% in 15 weeks without lowering iron, ferritin or vitamins A and E. — subjects with mild to moderate hypercholesterolemia; fiber n = 87, placebo n = 82 (n = 169) Evidence B source
  LDL-C -20 mg/dL (-0.51 mmol/L) (-12.1%) vs -1.9 mg/dL (-0.05 mmol/L) (-1.3%) placebo; no significant effect on iron, ferritin, vitamin A or E
• In 5 adults, 1.4 oz (40 g) of corn bran gave the lowest breath hydrogen of four fibers, a sign it is fermented little in the colon. — Five subjects consuming meals with 40 g of added fiber (n = 5) Evidence C source
  Mean breath H2 over 9 h: 7.5 ppm with corn bran vs up to 12.0 ppm with oat bran; peak at 5.6 h vs 8.2 h without fiber

What it does to your health

• In a crossover RCT of 20 adults, a muffin with 8.0-9.6 g fiber from corn bran was among the two most filling over 180 minutes. — Healthy men and women (N = 20), five breakfast visits (n = 20) Evidence B source
  Corn bran and resistant starch had the most impact on satiety; polydextrose behaved like the low-fiber muffin (1.6 g fiber)
• In 29 men with high cholesterol on a low-fat diet, adding 20 g corn bran for 6 weeks further lowered total cholesterol and triglycerides. — Twenty-nine sedentary men with hypercholesterolemia, aged 38 to 70 years (n = 29) Evidence C source
  Additional lowering of total cholesterol, triglyceride and VLDL-C vs low-fat diet; LDL-C and HDL-C not significantly altered

Safety, limits and interactions

• In 8 people with type 2 diabetes, 52 g a day of corn bran over 4 weeks lowered triglycerides and HbA1c but was poorly tolerated. — persons with type II diabetes; 10 subjects on 26 g and eight subjects on 52 g fiber source daily (n = 18) Evidence B source
  52 g corn bran: lower VLDL cholesterol, triglycerides and glycosylated Hb; poor subject tolerance with the particle size used
• In a 6-week RCT of 31 adults with excess weight, 25-35 g a day of corn bran arabinoxylan raised gas and bloating for the first 3 weeks, then symptoms faded. — adults with excess weight; arabinoxylan n = 15 vs microcrystalline cellulose n = 16 (n = 31) Evidence B source
  More GI symptoms vs cellulose in weeks 1-3 (p < 0.05), reverting to baseline toward the end; adaptation correlated with baseline Bifidobacterium longum (rs = 0.74)
• The FDA label for levothyroxine says dietary fiber may bind the drug and decrease its absorption from the gut. Corn bran is a fiber source but the label does not name it or give a dosing gap. — People taking levothyroxine sodium tablets Evidence E source
  Direction only: dietary fiber may bind levothyroxine and reduce its absorption; no size, no amount of fiber, no timing in this section

What people believe that the data does not support

• In an RCT of 48 women given 13-15 g fiber a day for 8 weeks, wheat, oat and corn bran changed fecal diacylglycerol markers differently. — Forty-eight women consuming a typical western diet, randomized to wheat, oat or corn bran (n = 48) Evidence B source
  Wheat bran lowered total fecal diacylglycerols; corn bran lowered only stearic-acid diacylglycerol; all raised fecal fat

Who this works differently for

• In 10 constipated women, 20 g a day of corn bran relieved symptoms better than wheat bran, while bran overall raised stool weight by 157%. — 10 constipated (less than or equal to 3 movements/wk) but otherwise healthy women (n = 10) Evidence B source
  Bran: fecal weight +157%, bowel movement frequency +55%, transit time -50%; corn bran better than wheat bran for symptoms
• In obese people with impaired glucose tolerance, 10 g a day of soluble corn bran hemicellulose for 6 months lowered HbA1c, unlike in healthy controls. — patients with impaired glucose tolerance with (20 subjects) or without (8 subjects) obesity and 10 healthy non-obese controls (n = 38) Evidence C source
  HbA1c decreased significantly in obese patients; post-OGTT curve improved in IGT, not in controls

What is still unknown

• A 2025 scoping review of 21 studies linked fiber-rich corn bran products to better blood lipids and glucose, and called for larger trials. — 21 human studies of corn flour consumption across the lifespan (n = 21 studies) Evidence C source
  Whole grain corn products high in corn bran associated with favorable lipid and glycemic profiles; long-term evidence lacking

The bottom line

Smaller studies point the same way and stay small. In 29 men with high cholesterol already on a low-fat diet, adding 20 g of corn bran for 6 weeks further lowered total cholesterol and triglycerides, with LDL and HDL unchanged, and the abstract gives no size for the drop. In a crossover trial of 20 healthy adults, a breakfast muffin with 8.0 to 9.6 g of fiber from corn bran was one of the two most filling of five over 180 minutes, judged on rating scales after a single meal. A 2025 scoping review of 21 studies linked whole grain corn foods rich in bran to better blood lipids and glucose. It did not pool results or rate their quality, and its authors asked for larger, longer trials. The three brans did not act alike. In 48 women given 13 to 15 g of fiber a day for 8 weeks, wheat, oat and corn bran each shifted fat markers in stool in a different way, and all three raised fecal fat. Breath hydrogen in 5 adults was lowest after 1.4 oz (40 g) of corn bran among four fibers, 7.5 ppm against up to 12.0 ppm with oat bran, an indirect sign that it is fermented little in the colon. Large amounts are where the trouble shows. In 8 people with type 2 diabetes, 52 g a day for 4 weeks lowered triglycerides and HbA1c, but they tolerated it poorly with the particle size used. In 31 adults with excess weight, 25 to 35 g a day of arabinoxylan isolated from corn bran raised gas and bloating for the first 3 weeks before symptoms faded. Obese people with impaired glucose tolerance saw HbA1c fall on 10 g a day of a soluble corn bran extract over 6 months, in a trial without a placebo group. We found no studies of corn bran in pregnancy or in kidney disease. On medicines, the FDA label for levothyroxine, the thyroid hormone tablet, says dietary fiber may bind the drug and decrease its absorption from the gut. The label does not name corn bran or give a gap between the two, so for anyone on levothyroxine, bran in the amounts these trials used is a question for the prescriber. Many of the people these trials studied, with diabetes or high cholesterol, take other regular medicines too, and we found no study of whether corn bran changes how those work, which is not evidence that it does not.

Sources

1. kbrn-r1-01 · reference dataset
   SR Legacy FDC 170289 Corn bran, crude: Fiber, total dietary 79 g | Energy 224 kcal | Carbohydrate, by difference 85.64 g | Protein 8.36 g | Total lipid (fat) 0.92 g | Iron 2.79 mg | Magnesium 64 mg | Selenium 16.5 ug | Lutein + zeaxanthin 1355 ug per 100 g
   USDA SR Legacy 2018 (FoodData Central), FDC 170289 Corn bran, crude · checked 2026-10-02
2. kbrn-r1-02 · reference dataset
   SR Legacy FDC 170289 Corn bran, crude: food_portion 1 cup 76 g || Fiber, total dietary 79 g per 100 g
   USDA SR Legacy 2018 (FoodData Central), FDC 170289 Corn bran, crude · checked 2026-10-02
3. kbrn-r1-08 · randomized controlled trial
   BACKGROUND: The study evaluated the blood cholesterol-lowering effects of a dietary supplement of water-soluble fibers (guar gum, pectin) and mostly non-water-soluble fibers (soy fiber, pea fiber, corn bran) in subjects with mild to moderate hypercholesterolemia (LDL cholesterol, 3.37-4.92 mmol/L). ... The mean changes from pre-treatment values in LDL-C, TC, and LDL-C/HDL-C ratio for subjects in the fiber group were -0.51 mmol/L (-12.1%), -0.53 mmol/L (-8.5%), and -0.30 (-9.4%), respectively. ... The fiber supplement had no significant effects (P > 0.05) on HDL cholesterol (HDL-C), triglyceride, iron, ferritin, or vitamin A or E levels.
   Am J Prev Med, 1999 · checked 2026-10-02
4. kbrn-r1-09 · controlled clinical trial
   Five subjects consumed meals containing no added fiber or 40 g of wheat bran (WB), corn bran (CB), oat bran (OB), or citrus flour (CF) replacing white flour. ... Mean H2 concentration (ppm), averaged over the 9 h test period, ranged from 7.5 (CB) to 12.0 (OB) and tended to increase with addition of OB, CF, or WB but decrease with addition of CB.
   Am J Clin Nutr, 1985 · checked 2026-10-02
5. kbrn-r1-03 · randomized crossover trial
   Healthy men and women (N = 20) participated in this acute, randomized double-blind, crossover study comparing the effects of 4 fibers and a low-fiber (LF) treatment on satiety. On 5 separate visits, fasting subjects consumed either a LF muffin (1.6 g fiber) or 1 of 4 high-fiber muffins (8.0-9.6 g fiber) for breakfast. ... Resistant starch and corn bran had the most impact on satiety, whereas polydextrose had little effect and behaved like the LF treatment.
   Nutr Res, 2009 · checked 2026-10-02
6. kbrn-r1-06 · controlled crossover trial
   SUBJECTS: Twenty-nine sedentary men with hypercholesterolemia, aged 38 to 70 years, participated in the project. ... Corn fiber supplementation resulted in an additional lowering of serum total cholesterol, triglyceride, and VLDL-C concentrations. Serum LDL-C and HDL-C concentrations were not significantly altered by corn fiber or wheat fiber supplementation.
   J Am Diet Assoc, 1995 · checked 2026-10-02
7. kbrn-r1-04 · randomized controlled trial
   In study A, 10 subjects consumed 26 g fiber source daily; in study B, eight subjects consumed 52 g fiber source. ... Consumption of 52 g corn bran decreased very low-density lipoprotein cholesterol, triglycerides, and glycosylated Hb, but subject tolerance was poor with the particle size used.
   Am J Clin Nutr, 1984 · checked 2026-10-02
8. kbrn-r1-05 · randomized controlled trial
   Here we analyzed findings from a six-week randomized controlled trial that evaluated GI symptoms to corn bran arabinoxylan (AX; n = 15) relative to non-fermentable microcrystalline cellulose (MCC; n = 16) at efficacious supplement doses of 25 g/day (females) or 35 g/day (males) in adults with excess weight. ... AX supplementation increased symptoms during the first three weeks relative to MCC (p < 0.05, Mann-Whitney tests), but subjects 'adapted' with symptoms reverting to baseline levels toward the end of treatment.
   Gut Microbes, 2024 · checked 2026-10-02
9. sf-fibdrug-r6-1 · agency advice
   Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the gastrointestinal tract.
   Levothyroxine sodium tablets, FDA-approved label, section 7.9, DailyMed set f059a576-bb4b-441d-917e-4338bc3df403, effective 2026-03-24 · checked 2026-10-08
10. kbrn-r1-11 · randomized controlled trial
    Forty-eight women consuming a typical western diet provided two 24-hour stool specimens and two sets of preintervention 4-day food records. They were randomly assigned to one of the fiber groups, namely, a wheat, oat, or corn bran supplement. They consumed their control diet plus 13-15 g of dietary fiber from each source for 8 weeks. ... Dietary wheat bran decreased the concentrations of total DAG and DAG containing lauric acid, myristic acid, palmitic acid, stearic acid, and linoleic acid, whereas oat bran increased the DAG composed of oleic acid and linoleic acid compared with the control diet. Corn bran decreased the DAG containing stearic acid.
    Gastroenterology, 1994 · checked 2026-10-02
11. kbrn-r1-07 · randomized controlled trial
    We evaluated the effect of two brans, wheat and corn (20 g/day), on fecal weight, fecal moisture content, bowel movement frequency, intestinal transit time, and symptoms in 10 constipated (less than or equal to 3 movements/wk) but otherwise healthy women. The administration of bran was associated with a significant increase in fecal weight (157%), bowel movement frequency (55%), and decrease in intestinal transmit time (50%). Percentage fecal moisture increased only with wheat bran (67.4-72.1%), whereas corn bran was significantly better than wheat bran in relieving symptoms of constipation.
    Am J Gastroenterol, 1982 · checked 2026-10-02
12. kbrn-r1-10 · clinical trial
    We examined the effect of soluble corn bran hemicellulose (CBH, 10 g/day) on glucose control and serum insulin in three groups: patients with impaired glucose tolerance (IGT) with (20 subjects) or without (8 subjects) obesity and with healthy non-obese controls (10 subjects). Long-term supplementation (6 months) with CBH decreased the post oGTT curve for patients with impaired mild Type II diabetes, but not that for the controls. Hemoglobin A1c decreased significantly during CBH supplementation in the obese patients
    Biosci Biotechnol Biochem, 1997 · checked 2026-10-02
13. kbrn-r1-12 · scoping review
    Twenty-one studies were included, investigating a wide range of health outcomes, including metabolic markers, growth metrics in infants, and risk of chronic diseases such as type 2 diabetes, obesity, and hypercholesterolemia. Findings indicated that whole grain corn products, particularly those high in fiber-rich corn bran, were associated with favorable effects on blood lipid and glycemic profiles. ... There is a clear need for more rigorous, larger-scale studies to better understand the long-term health impacts of corn flour consumption and its role in health.
    J Nutr, 2025 · checked 2026-10-02