If you're trying to eat a healthy, balanced diet, you've no doubt heard that whole grains are much better for you than refined grains. You may also have heard that bran is a healthy component of a diet. The difference between whole-grain wheat and wheat bran, in general terms, is that bran is a portion of the whole-wheat grain.
Whole Wheat
Whole wheat, or whole-grain wheat, consists of all parts of the wheat kernel. Like many other grains, wheat consists of three major anatomical parts. Deep inside the kernel is a protein-rich area called the germ, which nourishes the developing seed. There's also a large inner portion of the grain called the endosperm. This consists mainly of carbohydrate and is isolated from the rest of the kernel in refined flours. The hard outer casing, or shell, is called the bran.
Wheat Bran
Unlike the germ and the endosperm, the bran is meant to protect -- as opposed to nourish -- the wheat seed. It's made of a very tough material called cellulose. Drs. Reginald Garrett and Charles Grisham, in their book "Biochemistry," explain that cellulose consists of long chains of glucose molecules, just like starch. The glucose molecules are bonded to one another in a different pattern in cellulose than they are in starch, however, which renders the bran much tougher and more resilient than the starch endosperm.
Bran Nutrition
Because the glucose molecules that make up cellulose are connected differently than the glucose molecules that make up starch, you can digest starch for energy, but can't digest cellulose. As such, cellulose -- also called dietary fiber -- doesn't provide energy. Fiber is nevertheless an important part of diet, explains Dr. Lauralee Sherwood in her book "Human Physiology." It helps improve digestive function, assists in absorption of toxins in the digestive tract and reduces cholesterol absorption.
Whole-wheat Nutrition
If you eat whole wheat, you're getting all parts of the wheat kernel. You get carbohydrate from the endosperm -- bran also contains a small amount of carbohydrate -- which your cells use primarily for energy. You also get proteins and healthy fats from the germ. The bran doesn't contribute much in the way of calories or energy, but because it's a source of dietary fiber, it contributes to the overall nutritional value of whole wheat.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
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