For millennia, the grains humans ate came straight from the stalk. That means they got a carbohydrate package rich in fiber, healthy fats, vitamins, minerals, plant enzymes, hormones, and hundreds of other phytochemicals.
Even after we learned how to grind grain, we still got all of the goodness that grains pack in their three layers. Whole grains have a tough, fibrous outer layer called bran that protects the inside of the kernel. The interior contains mostly the starchy endosperm. Its job is to provide stored energy for the germ, the seed’s reproductive kernel, which nestles inside the endosperm. The germ is rich in vitamins, minerals, and unsaturated oils.
The invention of industrialized roller mills in the late 19th century changed what we got from grains. Milling strips away the bran and germ, making the grain easier to chew, easier to digest, and easier to keep without refrigeration (the healthy oils in the germ can turn rancid, giving the grain an off taste). Processing also pulverizes the endosperm, turning it from a small, solid nugget into millions of minuscule particles.
Refining wheat creates fluffy flour that makes light, airy breads and pastries. But there’s a nutritional price to be paid for refined grains. The process strips away more than half of wheat’s B vitamins, 90 percent of the vitamin E, and virtually all of the fiber. It also makes the starch easily accessible to the body’s starch-digesting enzymes.
A growing body of research shows that returning to whole grains and other less-processed sources of carbohydrates and cutting back on refined grains improves health in myriad ways.
The Way To Eat 