Grains might get the snub from the keto and paleo crowds, but they’re warmly embraced by nutrition scientists—especially whole grains.

Whole wheat, oats, brown rice, and other whole grains are linked to a reduced risk of cardiovascular disease, type 2 diabetes, obesity, constipation, and certain types of cancer. They are rich in fiber, vitamins, minerals, healthy fats, and phytonutrients, which are antioxidants or molecules with other protective qualities. And some choices are even healthier than others. But identifying those healthy choices takes a little grocery store sleuthing.

We should be eating more whole grains… Americans barely consume one serving daily when we should be at three or more. The Dietary Guidelines for Americans recommend that at least half our grains should be whole grains, but we’re not there yet either. Much of her research has been devoted to whole grain nutrition.

Whole vs. refined grains

A whole grain is a seed that grows into the corn, wheat, oats, or other grains we put on the table.

It has three parts: The outer bran layer; the middle endosperm, which comprises most of the grain; and a small germ. If these three components exist in a food in the same proportions as in the intact grain, it’s considered “whole grain,” according to the Food and Drug Administration (FDA). (Food manufacturers may add the three components separately to products for texture, taste, or other reasons.)

While some fringe wellness sites claim that grains are relatively new foods that our bodies aren’t evolutionarily equipped to handle, archeological evidence from late Neanderthals shows we’ve been eating whole grains for about 50,000 years. But it’s been just about 150 years since we began eating refined grains, which occurred after the invention of the roller mill, a device that removes the bran and germ.

What makes whole grains so protective?

When whole grains are processed, the bran and germ are discarded and you toss out fiber, vitamins, minerals, phytonutrients, and healthy fats. What remains is the endosperm—starch—with some protein and little else.

Thiamin, as well as other B vitamins and iron are added back to the “enriched rice” and “enriched flour” sold in the U.S. and other countries.

There’s a lot we don’t add back such as phytonutrients, or potassium and magnesium—two minerals Americans aren’t getting enough of. They help regulate blood pressure as well as muscle and nerve function. Magnesium is also part of our bone structure.

Another major fallout of refining: Loss of dietary fiber. There are three grams (g) of fiber in a cup of fresh corn kernels; but not even one gram in a cup of corn flakes, which is made with refined corn flour. Whole wheat pasta has more than double the fiber of regular.

Fiber-rich diets are linked to a slew of health benefits, such as a 15 to 30 percent lower risk of coronary heart disease (clogged arteries to the heart), stroke, type 2 diabetes, constipation, and colorectal cancer compared to low fiber diets. Higher fiber intake may also offer protection against depression and obesity. It’s even linked to a lower risk of death—from heart disease, stroke, or any cause.

Fiber helps us all along the digestive tract, starting with the mouth. High fiber foods take longer to chew, and when you slow down eating, you might take in fewer calories, which helps keep body weight down. It helps prevent constipation, and in the large intestine, fiber is fuel for beneficial gut bacteria. These bacteria produce short chain fatty acids which are linked to lower risk of colorectal cancer and can tamp down inflammation—a root cause of many chronic diseases.

But only 4 percent of Americans meet the fiber guidelines; lack of whole grains might be the main reason, notes Slavin.

Whole grains and the glycemic index

Some whole grain foods have another thing going for them: A low glycemic index (GI). This is a 1 to 100 ranking of carbohydrate-rich foods based on their effect on blood sugar. For the same number of grams, a low GI carbohydrate food (1 – 55) triggers a relatively small rise in blood sugar, a medium GI food (56 – 69) raises blood sugar further, and a high GI food (70-plus) even higher.

Keeping blood sugar in the normal range helps keep blood vessels and organs healthy. Substantial research finds that low GI diets are associated with a lower risk of developing type 2 diabetes, and studies suggest they might reduce risk for heart disease and certain cancers.

The glycemic index has been criticized because the same food can produce varying blood sugar responses in different people, or even in the same person depending on various factors. But the overall trends linking GI to type 2 diabetes are strong and consistent.

Better whole grains

In my view, a high-quality carbohydrate should have at least one of these features: low GI, high fiber, or whole grain. If you get all three in one food—that’s ideal.

Simple, intact, close-to-their-natural-form cooked whole grains, like steel cut oats, barley, and quinoa, tend to check all three boxes.

But GI goes up quite a bit [25 to 35 percent] when whole oat grains get crushed to form rolled oats, and only rises a little more when turned into flour.

Cooked wheat berries (which are intact wheat kernels) have a low glycemic index, whereas many whole wheat breads, which use whole wheat flour, have a high GI, often equivalent to white bread.

To understand this, it helps to understand starch’s structure: It’s simply long chains of glucose molecules bonded together. The starch molecule is much too large to be absorbed into the body. So, our enzymes cleave off glucose units—that’s what we absorb.

Enzymes make quick work of the finely ground particles in whole or refined wheat flour, sending a rush of glucose into the body. But with intact grains, even after chewing, large chunks remain. It takes the body a lot longer to bust through the wide surface area of tough fibrous bran.

And there’s another way certain types of fiber, such as beta-glucans in oats, slow down digestion and absorption—by forming a gel in the intestinal tract.

How to choose—and prepare—the best whole grains

It takes some sleuthing to bring home 100 percent whole-grain products. For example, “Made from whole grain” on the label might mean just a small fraction of the grain is whole—the rest is refined. “Wheat bread” might—or might not—contain any whole wheat. And the bread’s brown color? It could be food coloring.

While the Whole Grains Council stamp specifies the amount of whole grain, not all products carry it.

The labels are confusing for consumers. To cut through the noise, turn the package around and read the ingredient list carefully. Whole, as in whole wheat or whole rye means it’s a whole grain. Brown rice, oats, and quinoa, are always whole grains, they don’t need to be preceded by the word whole. But most other terms, like wheat, or organic, or semolina means the grain is most likely refined.

Cook whole grains in big batches—leftovers can be refrigerated for up to three days or frozen for up to six months. Whole grains are so easy to cook—just add water; equal parts water and broth are even tastier. Quinoa cooks fastest—just 20 minutes. It’s about 20 to 25 for farro and 40 to 50 minutes for brown rice.

Use whole grains as a recipe base such as the quinoa in Mexican-inspired “Easy Vegan Taco Skillet. Also, a whole wheat pasta fan as pasta’s structure tends to make it low GI, even if it’s white pasta. But with whole grain, you’re getting so much more nutrition.

Try new grains, like millet or buckwheat, to enjoy new flavours and take in a wider variety of fibre and other nutrients.