What Are the Three Parts of a Wheat Grain?

December 25, 2025 •

3 min read

Comprising about 83% of its total weight, the endosperm is the largest of the three parts of a wheat grain and is the primary source of white flour. The other two parts, the bran and the germ, are removed during the refining process, stripping away many of the grain's vital nutrients.

Quick Summary

The three parts of a wheat kernel are the bran, germ, and endosperm, each containing distinct nutrients like fiber, vitamins, minerals, and healthy fats. Their inclusion defines a whole grain, while their removal results in refined grain products.

Key Points

The Three Parts: A wheat grain consists of three primary components: the bran, the endosperm, and the germ.
Nutrient-Rich Bran: The bran is the outer layer, rich in fiber, B vitamins, antioxidants, and minerals.
Endosperm for Energy: The endosperm is the starchy core, providing carbohydrates and protein but fewer micronutrients than the other two parts.
Germ is a Powerhouse: The germ is the embryo, packed with healthy fats, vitamin E, and B vitamins.
Whole vs. Refined: Whole grains contain all three parts, while refined grains have the bran and germ removed during processing.
Healthier Choice: Whole grains offer superior nutritional benefits, including better digestive health and reduced risk of chronic diseases, due to their complete composition.

Understanding the Whole Grain

A wheat grain, also known as the wheat kernel or wheat berry, is the edible seed of the wheat plant, consisting of three parts: the bran, the endosperm, and the germ. For a grain product to be considered "whole grain," all three parts must be present in their natural proportions. This is a key distinction from refined grains, which often lack the bran and germ.

The Bran: The Fiber-Rich Outer Layer

The bran is the hard, multi-layered outer shell of the wheat kernel, making up about 14.5% of its weight. This protective layer is rich in dietary fiber, particularly insoluble fiber, which supports digestive health. The bran also contains antioxidants, B vitamins, and minerals like iron, zinc, and magnesium. It is removed during the milling process for refined flour.

The Endosperm: The Starchy Core

The endosperm is the largest part, about 83% of the kernel's weight, and serves as the food supply for the young plant. It is primarily a source of starchy carbohydrates and protein for human consumption, with fewer B vitamins and minerals than the bran and germ. Refined flour is made almost entirely from the endosperm.

The Germ: The Nutrient Powerhouse

The germ is the embryo of the wheat kernel and can sprout into a new plant. Although it's only about 2.5% of the kernel's weight, the germ is packed with healthy fats, essential fatty acids, vitamin E, B vitamins, minerals, and proteins. The germ's fat content can cause rancidity, leading to its removal in refined flour to extend shelf life.

The Difference Between Whole and Refined Grains

Processing wheat grains significantly impacts their nutritional value. Whole grains include all three components—bran, germ, and endosperm—while refined grains remove the bran and germ. This removal eliminates much of the fiber, vitamins, and antioxidants.

Comparison Table: Whole Grain vs. Refined Grain


Feature	Whole Grains	Refined Grains
Included Parts	Bran, Germ, and Endosperm	Endosperm only
Primary Nutrients	Fiber, B vitamins, minerals, antioxidants, healthy fats	Starchy carbohydrates and some protein
Milling Process	All three parts are milled, potentially ground into flour	Bran and germ removed, leaving only the endosperm for milling
Enrichment	Naturally nutrient-dense; no enrichment required	Many are enriched, with some B vitamins and iron added back synthetically
Fiber Content	High; aids in digestion and satiety	Very low, as fiber is concentrated in the bran
Shelf Life	Shorter due to fats in the germ potentially going rancid	Longer due to the removal of the germ

Health Benefits of Eating the Whole Grain

Choosing whole grains provides numerous health benefits due to their complete nutritional profile. The bran and germ contribute significantly to these advantages.

Key Health Impacts of Whole Grains

Improved Digestive Health: High fiber promotes regularity and supports gut health.
Better Blood Sugar Control: Fiber helps stabilize blood sugar, reducing the risk of Type 2 diabetes.
Enhanced Heart Health: Whole grains are linked to improved cholesterol levels and a reduced risk of heart disease.
Disease Risk Reduction: Antioxidants and phytochemicals in whole grains may lower the risk of certain cancers.
Weight Management: Fiber increases fullness, which can aid in weight control.

Learn more about whole grains from organizations like the Whole Grains Council.

Conclusion: The Importance of the Complete Wheat Grain

The bran, endosperm, and germ are the three vital parts of a wheat grain, each contributing unique nutrients. Whole grains, containing all three parts, are significantly more nutritious than refined grains, which lack the bran and germ. Consuming whole grains provides health benefits like improved digestion, better blood sugar control, and reduced risk of chronic diseases. Opting for whole grain foods is a valuable step towards a healthier diet.

Frequently Asked Questions

During the refining process, the wheat grain is milled to remove the outer bran and the inner germ, leaving only the starchy endosperm. This results in white flour with a finer texture but significantly less fiber and nutrients.

Whole grains are healthier because they contain the entire grain kernel, including the bran and germ, which are rich in fiber, vitamins, minerals, and antioxidants. These nutrients are mostly lost when the grain is refined.

The endosperm's primary function is to provide the energy supply for the seed to germinate. In human nutrition, it is primarily a source of starchy carbohydrates and some protein.

No. While enriched flour has some B vitamins and iron added back after processing, it does not contain the same amount of natural fiber, antioxidants, or other nutrients found in whole grain flour.

The germ contains healthy fats that can cause refined flour to go rancid quickly. Removing the germ extends the shelf life of flour and products made from it, but also removes many nutrients.

Yes, a processed grain can still be considered 'whole' if the final product contains all three original parts—the bran, germ, and endosperm—in the same proportions as the intact kernel.

To identify whole grain products, check the ingredient list for the word "whole" before the grain name, such as "whole wheat flour." The Whole Grains Council also offers a stamp to help consumers find whole grain products.

The bran and germ offer health benefits including improved digestion due to high fiber content, potential cancer risk reduction from antioxidants, and better cholesterol and blood sugar management.