05/05/1994

Research Helping Improve Everyone's Performance

AUBURN, Ala. - Whether you're running marathons or just running the rat race, nutrition can be a key to success. Research underway through the Alabama Agricultural Experiment Station (AAES) at Auburn University is helping identify which nutrients will help ensure that success.

Bob Keith, professor of nutrition and food science in Auburn University's School of Human Sciences, has been trying to demystify nutritional needs and claims. Keith's work, which is often conducted on athletes, has helped to verify the benefits of a variety of nutritional components including carbohydrates and vitamins B2 (riboflavin) and B1 (thiamine). Recently his work has been illustrating the many benefits of vitamin C in a stressful world.

"Stress is a strain, pressure or force exerted upon the body," explained Keith. "Short-term stress is beneficial, but prolonged stress can have detrimental effects."

According to Keith, stress can be physical (smoking or exhaustive exercise), psychological (job or school pressures) or social (peer pressure).

No matter what causes stress, the body's response is similar. Increased blood pressure and heart rate and release of certain hormones, such as cortisol and adrenaline, are typical responses. Prolonged stress can decrease immune system function, cause a loss of muscle tissue and increase the incidence of stroke, heart attacks and other conditions. Vitamin C has been shown to decrease blood pressure in some people and to exhibit other anti-stress properties.

"Historically, the Recommended Dietary Allowance (RDA) for vitamin C has been set at an amount that satisfactorily prevents symptoms of vitamin C deficiency," Keith continued. "However, current research is looking at vitamin C needs from the point of view of optimal health and the intake that might be needed to reduce the detrimental effects of stress."

Recently, the RDA for vitamin C was increased from 60 milligrams (mg) per day to 100 mg per day to cover the stress on the body from smoking cigarettes.

Exercise stresses the body. Like many other stressors, some exercise is beneficial, but excessive exercise can be harmful. For example, exercise is known to increase the production of the stress-related hormone cortisol, high concentrations of which can break down lean body mass and depress the immune system over a prolonged period. Since cortisol is an indicator of stress, exercise can be used as a model for determining how vitamin C might help the body cope with stress.

AAES studies have focused on the effects of consuming supplemental vitamin C while undergoing a strenuous exercise regimen. One study used trained male and female cyclists as subjects. Researchers first established the workload necessary on a stationary bicycle for each cyclist to maintain maximum heart rate. After receiving dietary vitamin C at the RDA of 60 mg per day for two weeks, the subjects rode for one hour at 80 percent of their maximum effort. They repeated the ride after receiving 600 mg for another two weeks.

Plasma cortisol concentrations, blood pressure measurements and working heart rates were all lower when the subjects received the higher amounts of vitamin C. This indicates that exercise-induced stress was reduced in subjects receiving higher amounts of vitamin C.

"These studies support the concept that vitamin C has some anti-stress properties," noted Keith. "Doses of vitamin C that were above current RDA values seemed to benefit subjects undergoing exercise stress as evidenced by reduced plasma cortisol and blood pressure rates."

Keith noted that these results do not necessarily mean people should take vitamin C supplements. "A well-balanced diet can provide plenty of the vitamin," he said. "For example, a cup of broccoli contains 120 mg of vitamin C; a 12-ounce glass of orange juice, 180 mg; one-third of a cantaloupe, 60 mg; and a baked potato, 30 mg. Other good sources of vitamin C include citrus fruits, strawberries, green peppers, and green leafy vegetables."

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News from:

Office of Ag Communications & Marketing

Auburn University College of Agriculture
Alabama Agricultural Experiment Station
3 Comer Hall, Auburn University
Auburn, AL 36849
334-844-4877 (PHONE) 334-844-5892 (FAX)

Contact Jamie Creamer, 334-844-2783 or jcreamer@auburn.edu
Contact Katie Jackson, 334-844-5886 or smithcl@auburn.edu

05/05/94