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You Asked For It: Question Authority

Nieman, David C. Dr.P.H., FACSM

doi: 10.1249/FIT.0b013e3181c63f68
DEPARTMENTS: You Asked For It: Question Authority

I know my diet is low in fiber from fruits, vegetables, and whole grains, but I am a runner and believe fiber intake is less important for my health than for my less active peers. What do you think - is fiber needed for healthy runners?

David C. Nieman, Dr.P.H., FACSM, is professor and director of the Human Performance Laboratory, Appalachian State University, in Boone, North Carolina; an active researcher; and author of several textbooks on health and fitness. Email your questions to


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A: Yes, I definitely recommend an emphasis on high-fiber foods for all people, physically active or not. The best evidence suggests that the health effects from regular exercise and a high-fiber diet are additive.

One of the strongest and most consistent findings from research conducted around the world in the last two decades is that a high dietary fiber intake from whole grains, fruits, and vegetables improves health and aids in weight management. These foods bring more to the table than just dietary fiber - they also provide many essential nutrients, antioxidants, and phytochemicals that reduce risk for a wide spectrum of chronic diseases.

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Here is a sample of recent research reports that demonstrate the vital importance of a high-fiber diet based on a variety of plant-based foods:

* A diet rich in whole grains helps reduce abdominal fat while lowering the risk of heart disease. A study in the American Journal of Clinical Nutrition shows that people who followed a weight loss program incorporating whole-grain breads, cereals, and other foods lost more body fat from the abdominal area than those who ate only refined grains such as white bread and rice (5). In addition, subjects on the whole-grain diet experienced a 38% drop in C-reactive protein, an indicator of inflammation in the body linked to heart disease.

* Research on 21,000 physicians during a 19-year period showed that consumption of whole-grain breakfast cereals lowered risk of developing type 2 diabetes (7). Physicians consuming seven or more breakfast cereal servings a week compared with one or none experienced a 38% lowered risk for type 2 diabetes.

* The Mediterranean diet is high in vegetables, legumes, fruits, nuts, whole grains, olive oil, wine, and fish. A large study of 400,000 men and women showed that a high conformity to the Mediterranean diet reduced death rates for heart disease and cancer, as reported in the Archives of Internal Medicine (9). The link between the Mediterranean diet and reduction in overall death rates from chronic disease was related (in order of importance) to moderate ethanol intake; low consumption of meat; high vegetable, fruit, and nut intake; high diet monounsaturated (olive oil)-to-saturated (butter, red meat) lipid ratio; and high legume consumption.

* In another study of 130,000 men and women followed for 16 years by researchers from the Harvard School of Public Health, adherence to the Mediterranean diet reduced the risk of developing Parkinson's disease by 25% (3). These researchers reasoned that a high consumption of fruit, vegetables, legumes, and cereals and a low consumption of meats provided plenty of dietary antioxidants and folate and a limited amount of saturated fat. Together, this dietary profile may have lowered oxidative stress, a major contributor to the development of Parkinson's disease.

* High fruit intake, especially apples and pears, lowered risk of lung cancer, according to German researchers who followed nearly 500,000 people for 6 years (8). Among current smokers, a high intake of root vegetables was linked to decreased lung cancer risk. Quercetin, a pigment in berries, onions, and the peels of apples, is a strong antioxidant and anti-inflammatory and tends to accumulate in the lungs when regularly consumed. Additional reports from the German study support a protective effect of a high fruit and vegetable consumption against colon cancer.

* Vegetarians compared with nonvegetarians live about 3.6 years longer and have lower rates of obesity, high blood pressure, type 2 diabetes, heart disease, and certain types of cancer (10). Physically active vegetarians have a lower risk for chronic disease than inactive vegetarians, and vegetarians who run have a better disease risk profile than nonvegetarian runners (2,11).

* Pooled data from 12 studies involving 280,000 individuals showed that an intake of five or more servings of fruits and vegetables per day compared with less than three servings was linked to a 17% reduction in heart disease risk (4).

* A high intake of broccoli and cauliflower (cruciferous vegetables) in a 4-year study of 30,000 men was associated with a 40% lowered risk of prostate cancer, according to Canadian researchers reporting in the Journal of the National Cancer Institute (6).

These are just a few of the many health benefits linked to high-fiber plant-based diets. A diet rich in fruits, vegetables, whole grains, nuts, and seeds (the so-called rainbow diet) not only provides high amounts of dietary fiber but also contributes antioxidants, folate, potassium, carbohydrate, and healthy types of fats, all of which are important for both athletic endeavor and disease prevention (see Table).

Fruits, nuts, and vegetables, reports the U.S. Department of Agriculture, play a significant role in human nutrition and, as a group, make significant contributions to overall U.S. diet intake, including 91% of total vitamin C, 48% of vitamin A, 30% of folacin, 27% of vitamin B6, 17% of thiamine, and 15% of niacin. Fruits and vegetables also supply 16% of magnesium, 19% of iron, and 9% of the calories. Nuts are a good source of essential fatty acids, fiber, vitamin E, and minerals.

Despite the proven health and nutrition benefits of fruits and vegetables, only 20% of men and 30% of women eat five or more servings a day, according to a report from the U.S. Centers for Disease Control and Prevention (1). This proportion has decreased from 42% of adults eating five or more fruits and vegetables a day in 1988. The average American has only one fruit serving and two vegetable servings per day.

Do all you can to add color and fiber to your diet by ingesting fruits, vegetables, and whole grains at each and every meal. In the American College of Sports Medicine, we are familiar with the Exercise is Medicine™ concept, but we must not forget that plant-based foods have many health-promoting substances that contribute to the concept of "food as medicine." As a runner, you have much to gain by emphasizing both exercise and healthy eating in your daily routine.

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© 2010 American College of Sports Medicine.