Whole grains include all three parts of a grain kernel: The bran, endosperm and germ.
Bran:
Is the multi-layered outer shell that protects the other two parts of the kernel from sunlight, pests, water, and disease. It is rich in dietary fibre, B vitamins, minerals such as magnesium, iron and zinc, phytochemicals and some protein.
Endosperm:
Is the middle layer tissue that surrounds the germ and is the largest portion of the kernel. The endosperm provides nutrition to the germinating seed and in human diet and contains carbohydrates predominantly starch, proteins and small amounts of vitamins and minerals.
Germ:
Is the inner core of the grain that will sprout into a new plant. It contains vitamins B and E, minerals, phytochemicals and unsaturated fats.
To be considered a whole grain, all parts of the grain—bran, endosperm and germ—must be included.