Fiber up--U study compares fruit, grain, and vegetable fiber

According to a University study, not all food fiber has equal heart-protection value.

By Mary Hoff

From eNews, July 8, 2004; Updated July 21, 2004

It's been called the "blockbuster special"--stewed prunes and oatmeal. Such high-fiber fare is good not only for encouraging intestinal action but also for helping keep hearts humming along. In recent years, numerous research efforts have uncovered the power of fiber-rich diets to reduce blood pressure, control blood sugar, and even lower "bad cholesterol" levels in our blood.

In a University study of more than 300,000 men and women published earlier this year, School of Public Health epidemiologist Mark Pereira supported and refined those findings suggesting that high-fiber diets can reduce the risk of heart disease. He and his colleagues found that for every 10 grams of fiber consumed, the risk of heart attack or other coronary heart disease (CHD) decreased by 14 percent. The risk of dying from CHD dropped 27 percent.

But they also found--armed with additional data from U. S. and European studies performed over the past 30 years--that the relationship between fiber consumption and healthy hearts is strongest for fruit (a 30 percent drop in deaths for each 10 grams of fruit fiber) and grains (a 25 percent drop in deaths), but indiscernible for vegetables. In fact, when they considered only vegetable fiber, the researchers saw no association with either CHD incidence or mortality.

Pereira says it's not evident why fiber from vegetables had no link to heart disease. But he suspects it may have to do with the types of vegetables we tend to eat--potatoes, corn, peas, and other highly processed vegetables rather than green, leafy types.

Pereira's research is especially timely given rising obesity levels and the popularity of fad diets. Pereira recommends a fairly simple formula for a heart-healthy life: Eat your fruits, whole grains, and green leafy vegetables; avoid juice, soda, and fast food; and don't go off the deep end in any one direction. "The one thing that is clear to me, and it is sort of old-fashioned, is the importance of moderation and balance," he says. And don't forget, he adds, "to be physically active on a daily basis."

Pereira recommends eating fruit instead of drinking fruit juice for heart-healthy nourishment because "juice has no fiber in it, and the sugar is concentrated so that product has a higher caloric value." Fruit juice with pulp is no better, he adds. For example, orange juice with pulp "contributes very minimal fiber," he says. "You might get about half a gram per serving in the pulp juices, and with the whole orange fruit, you get about 3 grams of fiber."

Table 1. Dietary fiber in fruits, nuts, vegetables and grains*

Vegetables, Serving size, Dietary fiber (g)

Beans (baked), 1 cup, 18.6

Broccoli tops, 1 cup, 5.6

Carrots 1 cup, 3.2

Fruits

Apple, 1 medium, 3.2

Banana, 1 medium, 5.9

Figs (dried), 2, 18.5

Grapes, green 20 1.1

Orange, 1 medium, 4.5

Strawberries, 1 cup, 3.3

Breads and Cereals

White bread, 1 slice, 0.8

Whole-wheat bread. 1 slice, 2.4

All-Bran, 1/2 cup, 9.9

Grape Nuts, 1 cup, 5.3

Nuts

Almonds, 10, 3.6

Brazil nuts, 10, 5.4

Peanut butter, 2 tablespoon, 2.1

*Paul AA, Southgate DAT: McCance and Widdowson's Composition of Foods. London: Medical Research Council, 1978.

**All foods fresh unless stated otherwise.

Table 2. Dietary fiber in a high-fiber menu

Meal, Dietary Fiber (g)*

Breakfast

1/2 c All-Bran, 10.2

1/2 c milk

2 slices whole-wheat toast w/margarine, 4.3

1 c strawberries, 3.1

Lunch

2 slices whole-wheat bread, 4.3

1 lettuce leaf, 0.4

2 slices Swiss cheese

1 large peach, 4.0

2 oatmeal cookies, 2.1

Dinner

3 oz. beef

1 baked potato with skin, 7.0

1 stalk broccoli, 8.2

1 bowl lettuce, 0.9

10 cherries, 1.0

Total dietary fiber, 45.5

*Paul AA, Southgate DAT: McCance and Widdowson's Composition of Foods. London: Medical Research Council, 1978.

Tables courtesy of the University of Minnesota Extension Service

From the original story in Medical Bulletin, spring 2004.