Refined grains include white rice, white bread, regular white pasta, and other foods that have been made with white flour (also called enriched wheat flour or all-purpose flour), including many cookies, cakes, breakfast cereals, crackers, and snack foods.

Whole grains contain three parts: the bran (outer layer), endosperm (middle layer), and germ (inner layer). The bran and germ are the most nutritious parts of the grain; they contain concentrated amounts of fiber, vitamins, minerals, and antioxidants. During the refining process, however, the bran and germ are removed from the whole grain. The endosperm, the part of the grain that is left after the refining process, is primarily composed of starchy carbohydrates and is low in nutrients. Some nutrients, including iron and a handful of B vitamins, are added back to refined grains and flours during manufacturing (hence the term “enriched wheat flour”), but these represent only a fraction of what is initially removed from the grain. For these reasons, refined grains do not provide the same health benefits as whole grains.

The type of carbohydrates you eat makes a big difference in the way you metabolize food and in the amount of energy you have. Refined grains are quickly digested into simple sugars and absorbed into your bloodstream; this can cause blood-sugar levels to spike and then quickly crash. These rapid swings in blood sugar can drain your energy and leave you feeling moody and tired. On the other hand, high-quality carbohydrates such as whole grains are rich in fiber, which helps temper blood sugars by slowing the absorption of sugar into your bloodstream after meals. They provide long-lasting energy that will keep you fueled for hours. That’s why it’s best to choose high-quality carbohydrates — which include whole grains as well as vegetables, fruits, beans, and legumes — instead of poor-quality carbohydrates, like refined grains, whenever possible.

Compared with diets high in refined grains, diets rich in nutritious whole grains reduce your risk of type 2 diabetes, cardiovascular disease, and high blood pressure. On the flip side, the diet high in refined grains can contribute to high triglycerides and increase inflammation throughout the body, which may worsen symptoms of arthritis. Refined grains may also stand in the way of weight loss; because they are low in fiber, they’re not as filling as whole grains and are much easier to overeat.

White bread, regular pasta, and other products made with “enriched wheat flour” or “all-purpose flour” are wheat-based and therefore contain gluten, so they should be avoided by people with celiac disease. In fact, all versions (including healthy whole-grain varieties) of wheat, rye, and barley contain gluten and must be avoided by people with celiac. If you have celiac disease, specifically choose gluten-free, whole grains like wild and brown rice, quinoa, amaranth, buckwheat, and whole corn and packaged foods made with these ingredients (and as an extra measure of precaution, be sure to check package labels).