A whole grain kernel contains three parts: the bran, the endosperm and the germ. The bran is the outer coating that protects the kernel. It is rich in fiber and contains B vitamins and other trace minerals. The endosperm is the middle layer that contains lots of carbohydrates and some proteins. The germ is the small core of the kernel that is full of antioxidants, vitamin E, B vitamins and healthy fats. The majority of grain eaten by most of the industrialized world today is refined wheat flour that contains only the endosperm. It is stripped of its outer bran and its internal germ, leaving essentially pure carbohydrate and a nominal amount of protein with very little fiber and nutrients remaining.
“Whole grain” means that the grain is left with its endosperm, bran and germ, meaning that it retains all of its nutrients. Whole grains have a less intense effect on blood sugar levels because the fiber in the bran of the grain kernel helps the grain to digest more slowly. This also helps you to stay full and sustain energy levels for longer.