Fueling Your Body: Carbohydrate Gets
the Gold
Your body is always burning a mixture of carbohydrate, fat, and
protein. The duration of exercise, intensity of exercise, level
of physical conditioning, and initial muscle glycogen levels will
determine which primary fuel your body will use.4In general, carbohydrate
is the primary fuel utilized during high intensity exercise. In
fact, about 55 to 75 percent of calories in the diet should come
from carbohydrate, and even more in individuals who compete in endurance
or ultra-endurance events.1 Whole grains, fruits, and vegetables
are excellent sources of carbohydrate.
With prolonged exercise, at lower intensities, fat (in the form
of fatty acids) becomes the primary fuel source. The shift to fatty
acids during exercise helps spare the carbohydrate (glycogen) stores
in your body and allows for prolonged exercise. However, while high
carbohydrate intake is recommended for performance, there is no
need to increase fat in the diet beyond the commonly recommended
10 to 30 percent of calories, as it is taken from storage sites
in the muscles when needed. Increasing fat in the diet is not recommended
for improving performance.5
Compared to carbohydrate and fat, protein is used only minimally
for fuel,4 as its primary function is for building and maintaining
the tissues of the body. Overall, a high-carbohydrate diet is most
important in ensuring optimal storage of carbohydrate in the body,
fueling the body for exercise, and supporting performance in both
the endurance6 and strength athlete.7,8 A vegetarian diet, which
emphasizes whole grains, fruits, vegetables, and legumes, provides
the high carbohydrate content to fuel your body through training
sessions and competition.
Power for Protein
Strength and endurance athletes both have increased protein needs.1
Protein, composed of chains of molecules called amino acids, plays
an important role in the building, maintenance, and repair of the
tissues of the body, including muscle. There are 20 different amino
acids in the foods we eat, but our body can make only 11 of them.
The 9 essential amino acids that cannot be produced by the body
must be obtained from the diet. A diet based on a variety of grains,
legumes, and vegetables easily provides all of the essential amino
acids. It was once thought that various plant foods had to be eaten
together to get their full protein value, a method known as "protein
combining" or "complementing." We now know that intentional
combining is not necessary to obtain all of the essential amino
acids.9Concentrated protein sources include tofu, soymilk, tempeh,
seitan, and various meat analogues, which can be purchased in any
health food store or the vegetarian section of your grocery store.
Protein requirements are very individualized and are primarily dependent
upon body size. The Recommended Dietary Allowance (RDA) for the
average, sedentary or lightly active adult is 0.8 grams per kilogram
of body weight per day.10For most people, this is more than enough.
However, some authorities believe that protein needs for athletes
may range from 1.2 to 1.7 grams per kilogram of body weight per
day for the highly active adult athlete.5,11 Tips for meeting your
protein needs are included in the table below.
It is important to keep in mind that while some protein will be
broken down into amino acids for fuel during exercise, the primary
role of protein is for structure and support. While protein needs
are increased in the diet of athletes, adequate (10 to 15 percent
of calories or enough to meet your calculated requirements), but
not excess, protein should be consumed. Protein should come from
plant sources, rather than meat, dairy products, and eggs, which
are devoid of fiber and complex carbohydrates. Emphasis should be
placed on a diet that is high carbohydrate to ensure that protein
is spared for those activities it does best: the building and repairing
of body tissues, including muscle.
Tips for Meeting Protein Needs
Top salads with a variety of beans, including chick peas, kidney
beans, great northern beans, and black beans. These legumes have
as much as 7 to 10 grams of protein per serving.
Shake it up! Blend non-dairy frozen desserts or soft tofu with your
favorite fresh or frozen fruits with soy or rice milk for a thick,
delicious, creamy, high-protein shake.
Marinated tempeh or veggie burgers grilled on a bun or added to
pasta sauce, offer a quick protein boost to any meal.
On the go? Sports bars and soy powder shakes are quick and convenient
supplements that can help increase the protein content of any well-balanced
vegetarian diet.
Staying Hydrated
Maintaining optimal hydration status is important in promoting
peak performance and preventing injury. Dehydration, defined as
body weight loss of 1 percent or more due to fluid loss, results
in a number of symptoms including headache, fatigue, heat intolerance,
and dark urine with a strong odor. More serious effects include
heat cramps, heat exhaustion, and heat stroke.12 By maintaining
a regular fluid schedule of at least eight 8-ounce glasses of water
per day, these symptoms are easily prevented.12
Fluid needs increase with exercise. Additionally, participating
in activity at high altitudes, low humidity, and high temperatures
can also increase fluid needs.12 The following guidelines, endorsed
by the American College of Sports Medicine, can help you stay hydrated:13
Two hours before exercise: Drink 17 ounces (or about 2 cups) of
fluid.
During exercise: Drink 4 to 8 ounces (or about 1/2 to 1 cup) of
fluid every 15 to 20 minutes.
After exercise: Drink 16 to 20 ounces (or about 2 to 2½ cups)
of fluid for every pound lost during exercise; weighing yourself
before and after exercise can help you determine your fluid loss.
Water is ideal as a fluid replacer, particularly for activities
lasting less than one hour. For those activities lasting more than
60 to 90 minutes, sports drinks containing carbohydrate or electrolytes
may be useful both during and following exercise.13,14 Electrolytes
and carbohydrate can also be easily ingested through food, in addition
to water, following a training session or event.
Ready, Set, Go!
The sports diet must be as carefully planned as the training regimen.
A well-balanced vegetarian diet, emphasizing consumption of a variety
of foods from the new four food groups—grains, legumes, fruits,
and vegetables—is an optimal sports diet for both performance
and health. By choosing generous servings of these foods with a
focus on variety and wholesomeness, your body will reap the benefits.
Whole grains: Choose whole wheat or enriched breads, cereals, rice,
and pastas. They are rich in complex carbohydrate, fiber, zinc,
and B vitamins. A single serving also provides about 2 to 3 grams
of protein.
Vegetables: Choose a variety of colorful red, orange, and yellow
vegetables in addition to leafy greens for vitamin C, beta-carotene,
and other antioxidants that will protect your body from the stress
of exercise. These foods also provide iron, calcium, fiber, and
a modest 2 grams of protein per serving.
Legumes: Choose a variety of beans (chickpeas, black beans, kidney
beans, great northern beans) as well as soymilk, tofu, tempeh, and
textured vegetable protein. They are not only high in protein (about
7 to 10 grams per serving), but also rich in complex carbohydrate,
fiber, iron, calcium, and B vitamins.
Fruits: Choose a variety of fruits and fruit juices for extra vitamins,
especially vitamin C.
Vitamin B12 supplement: A multivitamin/mineral supplement or vitamin
B12 supplement can be taken daily or every other day to cover nutritional
needs. Fortified foods, such as Kellogg's Cornflakes, Product 19,
and Total Cereal, or fortified soy and rice milks, may also contain
the active form of vitamin B12, cyanocobalamin.
References
1. Position of the American Dietetic Association
and the Canadian Dietetic Association: nutrition for physical fitness
and athletic performance for adults. J Am Diet Assoc 1993;93:691.
2. Houtkooper L. Food selection for endurance sports. Med Sci Sports
Exerc 1992;24(9suppl):S349-59.
3. Nieman DC. Vegetarian dietary practices and endurance performance.
Am J Clin Nutr 1988;48(3suppl):754-61.
4. Liebman M, Wilkinson JG. Carbohydrate Metabolism and Exercise.
In: Nutrition in Exercise and Sport, 2nd ed. Wolinsky I and JF Hickson,
eds. CRC Press: London,1994.
5. Williams C. Macronutrients and performance. J Sports Sci 1995;13:S1-10.
6. Jacobs KA, Sherman WM. The efficacy of carbohydrate supplementation
and chronic high-carbohydrate diets for improving endurance performance.
Int J Sport Nutr 1999;9(1):92-115.
7. Haff GG, Stone MH, Warren BJ, et al. The effect of carbohydrate
supplementation on multiple sessions and bouts of resistance exercise.
J Strength Cond Res 1999;13(2):111-7.
8. Leveritt M, Abernethy PJ. Effects of carbohydrate restriction
on strength performance. J Strength Cond Res 1999;13(1):52-7.
9. Position of the American Dietetic Association: vegetarian diets.
J Amer Diet Assoc 1997;97(11):1317-21.
10. Food and Nutrition Board. Recommended Dietary Allowances, 10th
ed. National Academy Press: Washington, DC,1989.
11. Lemon PW. Do athletes need more dietary protein? Int J Sport
Nutr 1995;5(suppl):S39-61.
12. Kleiner SM. Water: an essential but overlooked nutrient. J Amer
Diet Assoc 1999;99:200-6.
13. Convertino VA, Armstrong LE, Coyle EF, et al. American College
of Sports Medicine position stand. Exercise and fluid replacement.
Med Sci Sports Exerc 1996;28:i-vii.
14. Puhl SM, Buskirk ER. Nutrient Beverages for Exercise and Sport.
In: Nutrition in Exercise and Sport, 2nd ed. Wolinsky I and JF Hickson,
eds. CRC Press: London, 1994.
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