Whole grain refers to an entire grain of cereal, also known as a kernel. The kernel consists of three elements:1

• The bran: the fibre-rich outer layer of a kernel (12-17%)
• The germ: the nutrient-dense inner part of a kernel (approx. 3%)
• The endosperm: the central starchy part of a kernel (80- 85%).

To be defined as ‘whole grain’, a food product must retain the same relative proportions of its components (bran, germ and endosperm) as they exist in the intact grain.2

1.Healthgrain Forum (2011)
2. Dietary Guidelines for Americans (2010)