Health Gains from Whole Grains

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.

What Whole Grains Can Do For You

Harvard’s new Healthy Eating Plate reserves a quarter of your plate for whole grains, not just any grains.

As researchers have begun to look more closely at carbohydrates and health, they are learning that the quality of the carbohydrates you eat is at least as important as the quantity. Most studies, including some from several different Harvard teams, show a connection between eating whole grains and better health.

Cardiovascular Disease

Eating whole instead of refined grains substantially lowers total cholesterol, low-density lipoprotein (LDL, or bad) cholesterol, triglycerides, and insulin levels. Any of these changes would be expected to reduce the risk for cardiovascular disease. In the Harvard-based Nurses’ Health Study, women who ate 2 to 3 servings of whole-grain products (mostly bread and breakfast cereals) each day were 30 percent less likely to have a heart attack or die from heart disease over a 10-year period than women who ate less than 1 serving per week. (1) A recent meta-analysis of seven major studies showed that cardiovascular disease (heart attack, stroke, or the need for a procedure to bypass or open a clogged artery) was 21 percent less likely in people who ate 2.5 or more servings of whole-grain foods a day compared with those who ate less than 2 servings a week. (2)

Type 2 Diabetes

In a study of more than 160,000 women whose health and dietary habits were followed for up to 18 years, those who averaged 2 to 3 servings of whole grains a day were 30 percent less likely to have developed type 2 diabetes than those who rarely ate whole grains. (3) When the researchers combined these results with those of several other large studies, they found that eating an extra 2 servings of whole grains a day decreased the risk of type 2 diabetes by 21 percent.

More recent findings from this study (the Nurses’ Health Studies I and II) and the Health Professionals Follow-Up Study suggest that swapping whole grains for white rice could help lower diabetes risk: Researchers found that women and men who ate the most white rice—five or more servings a week—had a 17 percent higher risk of diabetes than those who ate white rice less than one time a month. Those who ate the most brown rice—two or more servings a week—had an 11 percent lower risk of diabetes than those who rarely ate brown rice. Researchers estimate that swapping whole grains in place of even some white rice could lower diabetes risk by 36 percent. (4)

Cancer

The data on cancer are mixed, with some studies showing a protective effect and others showing none. (5) A large, five-year study among nearly 500,000 men and women suggests that eating whole grains, but not dietary fiber, offers modest protection against colorectal cancer. (6, 7)

Digestive Health

By keeping the stool soft and bulky, the fiber in whole grains helps prevent constipation, a common, costly, and aggravating problem. It also helps prevent diverticular disease (the development of tiny pouches inside the colon that are easily irritated and inflamed) by decreasing pressure in the intestines.

Staying Alive

An intriguing report from the Iowa Women’s Health Study linked whole-grain consumption with fewer deaths from noncardiac, noncancer causes. Compared with women who rarely or never ate whole-grain foods, those who had at least two or more servings a day were 30 percent less likely to have died from an inflammation-related condition over a 17-year period. (8)

How Do Whole Grains Improve Health?

Whole grains don’t contain a magical nutrient that fights disease and improves health. It’s the entire package—elements intact and working together—that’s important.

The bran and fiber in whole grains make it more difficult for digestive enzymes to break down the starches into glucose. Soluble fiber helps lower cholesterol. Insoluble fiber helps move waste through the digestive tract. Fiber may also kindle the body’s natural anticoagulants and so help prevent the formation of small blood clots that can trigger heart attacks or strokes. The collection of antioxidants prevents LDL cholesterol from reacting with oxygen. Some experts think this reaction is a key early step in the development of cholesterol-clogged arteries. Phytoestrogens (plant estrogens) found in whole grains may protect against some cancers. So might essential minerals, such as magnesium, selenium, copper, and manganese. These minerals may also help reduce the risk for heart disease and diabetes. And then there are the hundreds of substances that haven’t yet been identified, some or many of which may play as-yet-undiscovered roles in health.

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Mixed grains

Try the recipe for Mixed up Grains, from Harvard University Dining Services.

1. Liu S, Stampfer MJ, Hu FB, et al. Whole-grain consumption and risk of coronary heart disease: results from the Nurses’ Health Study. American Journal of Clinical Nutrition. 1999; 70:412-9.

2. Mellen PB, Walsh TF, Herrington DM. Whole grain intake and cardiovascular disease: A meta-analysis. Nutr Metab Cardiovasc Dis. 2007.

3. de Munter JS, Hu FB, Spiegelman D, Franz M, van Dam RM. Whole grain, bran, and germ intake and risk of type 2 diabetes: a prospective cohort study and systematic review. PLoS Med. 2007; 4:e261.

4. Sun Q, Spiegelman D, van Dam RM, et al. White rice, brown rice, and risk of type 2 diabetes in US men and women. Arch Intern Med. 2010; 170:961-9

5. Jacobs DR, Jr., Marquart L, Slavin J, Kushi LH. Whole-grain intake and cancer: an expanded review and meta-analysis.Nutrition and Cancer. 1998; 30:85-96.

6. Schatzkin A, Mouw T, Park Y, et al. Dietary fiber and whole-grain consumption in relation to colorectal cancer in the NIH-AARP Diet and Health Study. American Journal of Clinical Nutrition. 2007; 85:1353-60.

7. Strayer L, Jacobs DR, Jr., Schairer C, Schatzkin A, Flood A. Dietary carbohydrate, glycemic index, and glycemic load and the risk of colorectal cancer in the BCDDP cohort. Cancer Causes and Control. 2007; 18:853-63.

8. Jacobs DR, Jr., Andersen LF, Blomhoff R. Whole-grain consumption is associated with a reduced risk of noncardiovascular, noncancer death attributed to inflammatory diseases in the Iowa Women’s Health Study. American Journal of Clinical Nutrition.2007; 85:1606-14.