What is Bran and How is it Made?

December 8, 2025 •

5 min read

Over half of the dietary fiber in a wheat kernel comes from its bran, the protective outer layer. This highly nutritious component is often removed during the processing of refined grains, leaving many to wonder, "What is bran and how is it made?" This guide explains the process and explores its numerous health advantages.

Quick Summary

Bran is the fiber-rich outer layer of cereal grains, separated during the milling of refined flour or rice. It is a concentrated source of dietary fiber, minerals, and vitamins, offering significant health benefits, especially for digestive and heart health.

Key Points

What Bran Is: Bran is the hard, fiber-rich outer layer of cereal grains, including wheat, oats, and rice.
How Bran is Made: Bran is produced during the grain milling process, where rollers crack the kernel and sifters separate the outer layers from the starchy endosperm.
Milling Methods: Modern roller milling efficiently separates bran, while traditional stone grinding results in whole grain flours that retain the bran.
Rich in Nutrients: Bran is an excellent source of dietary fiber, B vitamins, minerals like iron and magnesium, and beneficial antioxidants.
Digestive Health Benefits: The insoluble fiber in bran adds bulk to stools, promotes regular bowel movements, and acts as a prebiotic for healthy gut bacteria.
Versatile Ingredient: Bran can be easily incorporated into many foods, including muffins, cereals, smoothies, and soups, to boost nutritional content.
Different Types of Bran: Different brans offer distinct benefits; for example, oat bran contains soluble fiber for cholesterol management, while wheat bran is high in insoluble fiber for digestion.
Potential Drawbacks: The phytic acid in bran can inhibit mineral absorption, so balanced consumption is key. People with gluten intolerance should avoid wheat bran.

Understanding the Anatomy of a Grain

To understand what bran is, one must first recognize the structure of a complete, whole grain. A typical cereal grain kernel, such as wheat, consists of three primary parts: the endosperm, the germ, and the bran. The endosperm is the largest part, providing starchy carbohydrates to the seed. The germ is the embryo of the seed, packed with nutrients. The bran is the hard, protective outer casing, which is rich in fiber, B vitamins, minerals, and antioxidants.

The Purpose and Composition of Bran

The bran serves a critical function for the seed, shielding the endosperm and germ from sunlight, pests, and water. Its complex structure is composed of multiple layers, including the pericarp, the seed coat, and the nutrient-dense aleurone layer. The fiber in wheat bran is primarily insoluble, adding bulk to stools and aiding digestive transit. In contrast, oat and rice bran also contain significant amounts of soluble fiber, such as beta-glucan, known for its cholesterol-lowering properties. This diverse composition makes bran a nutritional powerhouse, far more valuable than a mere milling byproduct.

The Milling Process: How Bran is Made

Commercial milling is a precise, multi-stage process designed to separate the different components of the grain. The objective for producing refined grains (like white flour or white rice) is to separate the starchy endosperm from the bran and germ. The bran is produced as a byproduct during this separation process.

Stages of Modern Roller Milling

The journey from whole grain to separated bran involves several key mechanical steps:

Cleaning and Tempering: The raw grain is first meticulously cleaned to remove any impurities, such as stones and weed seeds. Following this, it undergoes a conditioning process called tempering, where moisture is added. This toughens the bran layers, making them easier to separate, and mellows the endosperm.
Breaking: The tempered grains are passed through a series of grooved steel "break rolls" that rotate at different speeds. These rollers crack the kernel open and scrape the endosperm away from the bran.
Sifting (or Bolting): After each pass through the break rolls, the cracked grain is sent to large, vibrating sieves known as plansifters. These finely meshed sieves sort the particles by size, separating the bran flakes from the finer endosperm particles and germ.
Purifying and Reduction: The process continues with a purifier system that uses sieving and air currents to refine the separation, ensuring only endosperm is ground into flour. Any remaining fragments of endosperm still attached to bran particles are sent through 'tail milling' for further reduction. The resulting bran is collected and packaged for sale or other uses, such as animal feed.

Stone Grinding: An Alternative Method

While modern roller milling is efficient for creating refined products, traditional stone grinding offers a different result. In this method, the entire grain is crushed between two large stones. This process, by its nature, cannot achieve the clean separation of bran and germ from the endosperm that roller milling does. As a result, stone-ground flours (including wholemeal) retain most or all of the bran and germ, which is why they have a coarser texture and more pronounced flavor than refined flours.

Health Benefits of Bran

Incorporating bran into your diet provides a significant nutritional boost. Its health benefits are well-documented and recognized by authorities such as the European Food Safety Authority.

Promotes Digestive Health: The high concentration of insoluble fiber in bran acts as a prebiotic, feeding beneficial gut bacteria and increasing stool bulk. This aids regular bowel movements and can help prevent or relieve constipation.
Reduces Chronic Disease Risk: Studies suggest that the fiber and antioxidants (such as phenolic compounds and lignans) in bran may help lower the risk of chronic diseases. This includes a reduced risk of colon and breast cancers by preventing tumor growth and regulating estrogen levels.
Supports Heart Health: High-fiber diets have been consistently linked to a decreased risk of heart disease. The fiber and other compounds in bran can help lower total cholesterol and triglyceride levels.
Aids in Weight Management: The high fiber content promotes a feeling of fullness, which can help regulate appetite and reduce overall calorie intake.

Comparison of Wheat Bran and Oat Bran

Choosing the right type of bran depends on individual health goals, as different cereal brans offer distinct nutritional profiles and benefits. The following table compares the key aspects of wheat bran and oat bran.


Aspect	Wheat Bran	Oat Bran
Primary Fiber Type	Insoluble fiber	Soluble fiber (especially beta-glucan)
Key Health Benefits	Increases stool bulk, aids constipation, supports gut bacteria as a prebiotic	Lowers cholesterol, stabilizes blood sugar, promotes satiety for weight management
Texture and Flavor	Coarse, nutty flavor	Creamier texture, milder flavor
Usage	Added to breads, muffins, cereals, and smoothies for bulk and texture	Used in hot cereals, muffins, and recipes aiming for creaminess

How to Incorporate Bran into Your Diet

There are many ways to add bran to your daily meals. For baked goods like muffins and breads, you can substitute some of the all-purpose flour with bran to boost the fiber content. Other simple methods include:

Sprinkling it over your morning oatmeal or yogurt.
Blending it into a breakfast smoothie.
Using it as a fibrous breading for chicken or fish.
Stirring it into soups, stews, or casseroles for added thickness and nutrition.

The Importance of Gradual Increase

When adding more bran to your diet, it is important to do so gradually to allow your digestive system to adjust. A sudden increase in fiber can lead to bloating and discomfort. It is also crucial to increase your fluid intake alongside your fiber consumption to help with digestion.

Conclusion

Bran is far more than a simple byproduct of the milling process; it is a nutrient-dense component of cereal grains packed with dietary fiber, vitamins, and minerals. Created by separating the outer layers of the grain during milling, bran is a versatile ingredient that offers substantial health benefits, from promoting digestive regularity to potentially reducing the risk of chronic diseases. Understanding what bran is and how it's made reveals its true value as a vital part of a healthy diet.

Frequently Asked Questions

A whole grain contains all three parts of the grain kernel: the bran, the endosperm, and the germ. Bran, by itself, is just the outermost, fiber-rich layer of that kernel. When you eat whole grains, you consume the bran and all its nutrients, but bran can also be separated and consumed on its own.

Yes, bran can be beneficial for weight management. Its high fiber content helps you feel full for longer periods after eating, which can reduce your overall calorie intake throughout the day. It is an excellent, low-calorie way to boost satiety.

No, wheat bran is not gluten-free as it comes from the wheat kernel and contains gluten. Individuals with celiac disease or gluten intolerance should avoid wheat bran and opt for gluten-free alternatives like oat bran (if processed in a gluten-free facility), rice bran, or corn bran.

To avoid digestive discomfort, introduce bran into your diet gradually. Start with small amounts, such as a tablespoon on your cereal, and increase slowly as your body adjusts. It is also vital to increase your fluid intake to help the fiber pass smoothly through your system.

Bran is found in many foods, including whole-grain cereals and breads, but it is also available as a separate product. Common foods include bran muffins, oatmeal (contains oat bran), and breakfast cereals like bran flakes.

Yes, there are differences. Wheat bran is rich in insoluble fiber, which is highly effective for promoting digestive regularity. Oat bran contains more soluble fiber (beta-glucan), which is particularly effective at lowering cholesterol levels.

Bran contains phytic acid, which can bind to minerals like iron, zinc, magnesium, and calcium, potentially inhibiting their absorption. For individuals with a balanced diet, this is not usually a concern. However, those relying heavily on high-phytate foods or with marginal mineral intakes should be aware and ensure their diet is varied.