NOVEMBER / DECEMBER 2004

AROUND HARVARD

This article originally appeared in the October 2004 Harvard Men’s Health Letter and is provided courtesy of Harvard Health Publications.

Whole grains: Why the fuss?

We hear it so often that it hardly registers: Eat your fruits, vegetables, and whole grains. The merits of fruits and vegetables seem pretty clear, but do whole grains deserve their place in the trinity? Are they really better than refined grains?

A kernel of history
All grains — including wheat, oats, rye, and barley — grow as kernels. Each kernel has three layers: bran, on the outside, germ, in the center, and endosperm, between the others (see “The three layers of grain,” below). The endosperm contains most of the starch, the germ contains the majority of the vitamins, minerals, and oils, and the bran contains the bulk of the bulk, the dietary fiber.

Throughout most of human history, people used whole kernels to make bread and other grain products. Whole grain, in fact, is still the rule in much of our world. But bread baked from whole grains tends to be coarse, dense, and dark. It didn’t take long for millers to learn how to separate a kernel of grain into its three parts; the next step was to use the endosperm for baking. The result is lighter, whiter bread, which quickly became the favorite of folks who could afford it. But another result is that the bran and germ are discarded — along with most of the vitamins, minerals, and fiber.

With the industrial revolution, milling became mechanical and refined grains fell in price. In part, perhaps, because it had been a symbol of privilege, white bread quickly became the standard fare; in the United States, the changeover occurred principally in the 1880s. Refined grains retain their primacy in America today. Foods made from refined grains contribute to obesity, heart disease, and diabetes — all unfortunate signs of an affluent society.

What’s missing?
Separating the wheat from the chaff is one thing; extracting the endosperm from the bran and germ, is quite another. Bran constitutes about 15% of a kernel of whole grain; germ, 3%; refined flour contains less than a tenth of a percent of each. Refining removes about 25% of the selenium, depriving men of a substantial amount of the mineral that may reduce the risk of prostate cancer. The table on below illustrates some of the other nutritional differences between whole and refined flour.

Putting it back
Human beings are ingenious creatures. First, they learned to remove the vitamins and minerals from grains; next, they learned to put them back.

During the first half of the 20th century, nutritional deficiency diseases became common in many parts of the United States. For example, in 1928 about 200,000 cases of pellegra were recorded, 7,000 of which were fatal. Refined grain wasn’t the only culprit, of course, but pellegra can be prevented by just 16 milligrams of niacin (vitamin B) a day. In response, many bakers began to add vitamins to flour in the 1930s. In 1941, the surgeon general made it a priority in order to “make our men as good as our machines.” For the past 60 years, the FDA has mandated the addition of nutrients to refined flour; the list has expanded to include niacin, thiamin, riboflavin, iron, calcium, vitamin D, and, folic acid. Every product made from “enriched” or “fortified” flour has these nutrients added to meet specific standards.

Still missing
Fortification restores some of the lost vitamins and minerals to refined flour. But others, including selenium, are still lacking. It’s easy enough to take a vitamin pill to make up the difference, but no vitamin or mineral will replace the dietary fiber removed by milling.

What is fiber?
Your mother called it roughage and her mother called it bulk. Today, though, chemists call it a polysaccharide polymer containing at least 20 sugar residues, and nutritionists call it dietary fiber. By any name, dietary fiber is a complex carbohydrate made up of dozens, even hundreds, of sugar molecules that link to form large, branched chains.

Fiber forms the structural backbone of plant stems, seeds, and leaves as well as the bran layer of grain. Although fiber is found in many plants and vegetables, it’s entirely absent from all animal cells and from foods derived from animals and fish.

Unlike other complex carbohydrates such as starch, dietary fiber cannot be broken down by human digestive enzymes, so it can’t be absorbed by the body. That means it has very little caloric value — but it has plenty of nutritional value.

Fiber and health
There are two types of dietary fiber: soluble and insoluble. Both are important for health. Insoluble fiber draws water into the intestines, making the feces bulkier and easier to pass; it helps promote intestinal health by reducing the risk of hernias, hemorrhoids, and diverticulosis. Soluble fiber has less effect on the intestines but more on the metabolism; it delays the stomach’s emptying, producing a feeling of fullness that may help prevent overeating. It also slows the absorption of carbohydrates, reducing insulin levels and helping to boost HDL (“good”) cholesterol; and it binds bile acids, reducing LDL (“bad”) cholesterol levels in the blood. Although all foods rich in fiber have both varieties, some are better sources of one type or the other; wheat and rye, for example, provide mostly insoluble fiber, while oats and barley are rich in soluble fiber.

People who eat a high-fiber diet enjoy a reduced risk of heart disease, diabetes, obesity, and nonmalignant intestinal disorders.

Whole grains are far from the only way to get dietary fiber; fruits, vegetables, nuts, and seeds are also good sources. But while some of these foods are very high in fiber (beans, prunes, figs), others have surprisingly little (lettuce, celery, cauliflower). It’s hard to get the fiber you need just from fruits and vegetables; for example, you’d need to eat about seven apples or eight cups of broccoli to do the job. Fruits and vegetables should, of course, be an important part of your diet — but so should whole grains.

Whole grains and disease
Like other fiber- and vitamin-rich foods, whole grains can help to promote health. For example, more than a dozen studies have evaluated whole grain consumption and heart disease; on average, they found that eating lots of whole grains was associated with a 26% reduction in risk. Similarly, a Harvard study of 75,571 women found a strong benefit against strokes; women who ate the most whole grains enjoyed a 31% reduction in strokes, even after other risk factors were taken into account. It’s much the same story for diabetes; another Harvard study found that eating a lot of whole grains reduced the risk of diabetes by 38% — but a high intake of refined grains was associated with a 31% increase in the likelihood of diabetes.

Heart disease, stroke, and diabetes certainly make a strong case for whole grains. But there’s more, especially for men. Fiber got bad press in 2000 when a series of studies from Harvard and elsewhere found that it does not reduce the risk of colon cancer in men or women. This news was a major disappointment, but two 2003 studies are restoring optimism. In Europe, the EPIC Study of 519,978 adults found that a high consumption of dietary fiber was linked to a 25% reduction in the risk of colon cancer. In the United States, a study of 33,971 people linked dietary fiber to a 27% lower risk of adenomas, the polyps that can develop into colon cancer. And another study found that eating cereals and other whole-grain products was associated with a significantly reduced risk of dying from prostate cancer.

What’s the bottom line on whole grain? According to the Iowa Women’s Health Study, it’s longevity; women who ate mostly whole grains had a 7% lower mortality rate than those who ate mostly refined grains. And a Harvard study of 86,190 health professionals found that the men who ate whole-grain cereals most often were 17% less likely to die during the five-year study than those who banned the bran.

Going with the (whole) grain
Fruits and vegetable are excellent for health, contributing vitamins, minerals, and many other nutrients as well as fiber. Whole grains can never replace fruits and vegetables in a healthful diet, but the reverse is true as well. A Harvard study of 43,757 American men, in fact, found that all forms of dietary fiber reduce the risk of heart disease, but cereal fiber was more protective than fruits and vegetables. For optimal health, it’s not either/or but both.

Americans should get at least 25 grams of dietary fiber a day; in this era of refined food, unfortunately, the average is less than half that.

The U.S. Department of Agriculture’s Food Pyramid Guide calls for 6–11 servings of grains a day; the lower number should suffice for small, sedentary women, the higher one for large, physically active men. Although many experts put the number much higher, the USDA says that at least three of the daily portions should be whole grains — but the average American man eats less than one.

Make whole grains an important part of your daily diet. Look for products that list whole grains first on their ingredient labels; “100% whole grain” foods are best. Don’t be fooled by terms like “multigrain,” “six-grain,” or “made with unbleached flour.” They are likely to contain mostly refined grains, as are dark-colored rye and wheat breads that are not labeled whole grain.

Eat a variety of whole grains. Oats and barley, for example, will give you soluble fiber; whole wheat and corn will supply insoluble fiber. Experiment with new grains, such as bulgur, millet, and quinoa.

Cereal is the best way to get whole grains. Look for a product that provides at least 5 or 6 grams of fiber per serving; All-Bran, Fiber One, 100% Bran, Oat Bran, oatmeal, and Raisin Bran are examples. Add fruit and nonfat milk, and you’ll have an ideal breakfast or, for that matter, a fine late-night snack.

Get your whole grains in breads and muffins. Experiment with whole wheat pasta. Try barley or brown rice instead of potatoes. Be creative. Most men can learn to enjoy whole grain foods, but those who don’t can take supplements of psyllium (Metamucil, Perdiem, and other brands), a natural grain from the Indian subcontinent.

People who are used to refined grains may regard whole grains as a novelty, but it’s really a case of getting back to basics. You may get a little gassy, but in the end, whole grains are worth the fuss — it’s basic.

The three layers of grain A kernel of grain has three layers, and each has nutritional value. The inner zone is the germ; it contains vitamins, minerals, and oils. The middle layer is the endosperm, containing most of the starch along with vitamins and minerals. The outer bran layer provides dietary fiber. Refining removes the bran and germ, leaving lighter, whiter fiber which has lost many of its nutrients.

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