Download Carbohydrate Requirement

NUTRITIONAL
RECOMMENDATIONS FOR
ATHLETES
By: Matt Eshelman, B.S. Exercise Science
E: [email protected]
W: www.srqperformance.com
INTRODUCTION
Proper nutrition is an important consideration for athletes who seek to maximize their
performance. There is no diet that directly increases strength, power, or aerobic endurance,
but an adequate diet allows an athlete to train and compete to the best of their ability. The
ideal diet for an athlete depends on many factors such as age, body size, genetics, and
environmental training conditions, as well as on duration, frequency, and intensity of training
sessions.
To support the demands of training and competition an athlete must consume a balanced diet
that provides all the essential nutrients: carbohydrate, protein, fat, water, vitamins, and
minerals. The two most fundamental components of a diet are appropriate calorie levels and
appropriate nutrient levels to prevent nutrient deficiency or toxicity. A simple tool to establish
the adequacy of an athlete’s diet is MyPyramid (www.MyPyramid.gov). This website was
developed by the U.S. Department of Agriculture and the U.S. Department of Health and
Human Services in 2005. MyPyramid combines the outdated “Food Guide Pyramid” with
inclusion of physical activity and the latest nutritional science. This tool displays the types and
amounts of food to eat on a daily basis from each of the five major food groups: grains,
vegetables, fruits, milk, and meat and beans. Although the basic guidelines in the pyramid are
universal, athletes have different needs from those of the general population. In the following
pages I will provide general recommendations for consumption of macronutrients (protein,
carbs, fat), micronutrients (vitamins and minerals), as well as fluid and electrolytes for athletes.
ENERGY REQUIREMENTS
Energy is commonly measured in calories (kcal). The number of calories an athlete needs is based on
body size, physical demands of the sport, length of training, training environment, and age. Energy
requirement is defined as enery intake equal to expenditure, resulting in constant body weight.
Consuming more calories then you burn results in weight gain, and consuming less calories then you
burn results in weight loss. The energy requirement is determined by three factors:
1. Resting Metabolic Rate: calories required to maintain normal body function. (breathing, cardiac
funtion, thermoregulation).
2. Thermic Effect of Food: increase in energy expenditure above the resting metabolic rate that
can be measured for several hours after a meal (digestion, absorption, metabolism, storage).
3. Physcial Activity: calories required expended through physical actity. Dependant on frequency,
duration, and intensity.
All of these factores are affected directly or indirectly by age, genectics, body size, body
composition, environmental temperature, and training conditions. Table 1.1 provides an estimated
daily caloric need based on gender and activity level. Most of you reading this will be classified in the
moderate or heavy activity level due to the demands of your sport.
Table 1.1: Estimated Caloric Needs Based on Activity Levels of Athletes
Male
Activity Level
Light
Moderate
Heavy
Kcal/pound
17
19
23
Kcal/kg
38
41
50
Female
Kcal/pound
Kcal/kg
16
35
17
37
20
44
*Adopted from Esssentials of Strength Training and Conditioning by the National Strength and Conditioning Association. (2005).
For example: The energy requirement of a 200lb male athlete with a heavy activity level is
4,600 kcal. 200 x 23 = 4,600 kcal.
My Daily Caloric Estimate: ________________
*Please note that this is merely an estimate. Monitoring of body weight will provide information if more or less
calories are needed.
MACRONUTRIENTS
Macronutrients are nutrients that are required in significant amounts in the diet. Three
important classes of macronutrients are protein, carbohydrates, and fat.
Note: All recommendations are expressed in grams per kilogram of body weight.
1 kg = 2.2 pounds. For example: A 200lb athlete weighs 90.72kg. 200/2.2 = 90.72kg
My Body Weight: ________kg
Protein
Amino acids are the building blocks of protein and when combined together they form the
thousands of various proteins occurring in nature. Proteins in the human body (muscle, bone, &
organs) are composed of 20 amino acids. More than half of these amino acids are produced in
the human body and are commonly known as “non-essential” amino acids because they do not
need to be consumed in the diet. Nine of the amino acids are termed “essential” because they
are not produced by the human body and therefore must be consumed through the diet (Table
1.2).
Table 1.2: Essential and Nonessential Amino Aids
Essential
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
Nonessential
Alanine
Arginine
Asparagine
Aspartic acid
Cysteine
Glutamic acid
Glutamine
Glycine
Proline
Serine
Tyrosine
*Adopted from Esssentials of Strength Training and Conditioning by the National Strength and Conditioning Association. (2005).
The amino acid content of a dietary protein affects its value in supporting growth and tissue
maintenance. Whether the protein supplies amino acids in amounts proportionate to the
body’s needs determines the protein quality. A high quality protein refers to a protein with an
amino acid pattern similar to that needed by the body; high quality proteins include eggs, meat,
fish, and dairy products. Proteins that are deficient in one or more of the essential amino acids
(grains, vegetables, beans) are referred to as low quality proteins. This presents a problem for
vegetarians that only consume plant proteins. When relying on low quality proteins it is
important to consume a variety of plant foods so that all essential amino acids are consumed
on a daily basis. For example: beans and rice, corn and beans, and peanut butter and bread.
Protein Requirement
Both aerobic endurance training and resistance training increase the body’s need for protein.
This increased demand for protein is the result of tissue damage and using protein as a fuel
source.
Research suggests that the protein requirement for an aerobic endurance athlete is 0.8 to
1.4g/kg of body weight. Heavy resistance training can increase protein requirements to as high
as 1.7g/kg of body weight. Because most athletes do not fall neatly into one category, a general
recommendation of 1.5 to 2.0g/kg of body weight ensures adequate protein intake. Expressed
as a percent of daily caloric intake, a common protein intake recommendation is 10 to 15%.
For example: The protein requirement of a 90kg strength athlete is 135-180g of protein/day.
My Daily Protein Requirement: _____________ g/day
Carbohydrates
The primary role of carbohydrate in human physiology is to serve as an energy source. The
importance of carbohydrates to an athlete’s diet has been shown in numerous studies which
have documented an increase in aerobic endurance, work output, and high-intensity exercise
performance. Breads, cereals, pasta, fruits, and starchy vegetables are promoted to athletes as
ideal sources of carbohydrates. All types or dietary carbohydrate are effective with the fuel
they need to perform. Consumption of carbohydrate low on the glycemic index (GI) is desirable
except for immediately after exercise when consumption of high GI carbohydrates combined
with quick digesting whey protein promotes recovery. Use the internet to examine the GI of
various foods.
Carbohydrate Requirement
Aerobic endurance athletes who train for long durations (over 90 or more daily) should
replenish glycogen (stored carbohydrates) levels by consuming maximal levels of
carbohydrates, approximately 8-10g/kg of body weight. This level has been shown to
adequately restore skeletal glycogen (stored carbohydrates) within 24 hours. Athletes who
would benefit from this level of carbohydrate intake are endurance athletes (rowers, distance
runners, cyclists, triathletes, soccer). Carbohydrate intake of 5 to 6g/kg of body weight appears
adequate to support performance of strength, sprint, and skill athletes (basketball, football,
volleyball, sprinters).
For example: The carbohydrate requirement for a 68kg lightweight rower is 544-680g/day.
The carbohydrate requirement for a 90.9kg football player is 455-546g/day.
My Daily Carbohydrate Requirement: ______________ g/day
Fiber
A diet low in fiber is associated with several disorders such as constipation, heart disease, color
cancer, and diabetes. The recommended intake of dietary fiber is 25 to 38g/day. Foods rich in
fiber include oatmeal, whole wheat bread, popcorn, raspberries, and pears.
My Daily Fiber Recommendation: ____________ g/day
Fats (Lipids)
Fats include triglycerides (oils) as well as related fatty compounds that are important to the
structure and function of cells. Fat in food is often perceived negatively by athletes, but
avoidance can lead to nutrient deficiencies which can harm performance. Body fat is necessary
for insulation and protection of organs and for hormonal regulation. Fat also serves as a carrier
for the fat-soluble vitamins and essential fatty acids. Food sources of dietary fat are red meats,
nuts, and oils.
Fat Requirement
The recommendation for the general public is that fat intake should constitute 20-35% of total
daily calories consumed, with less than 10% coming from saturated fats. This
recommendation is generally given to reduced reduce the risk of heart disease. Fat guidelines
for athletes may be higher than the standard “heart healthy” guidelines. Research shows that
during periods of heavy aerobic endurance training increases in fat up to 50% of total calories
have been reported without negatively effecting body fat. A fat intake over 30% is common
among elite athletes. Diets extremely low in fat (15% of daily calories or less) have been shown
to decrease testosterone production, thus decreasing metabolism and muscle development.
For example: The fat requirement for a 68.2kg lightweight rower who consumes
3400kcal/day would be 680 to 1700g/day.
My Fat Requirement: ____________ g/day
MICRONUTRIENTS
A micronutrient is a nutrient that is required in small amounts in the diet. The two primary
types of micronutrients are vitamins and minerals.
Vitamins
Vitamins are organic substances that are not made by the human body, so they must be
obtained from food sources or supplementation. Vitamins A, B, C, D, E, and K are vital for health
and athletic performance.
Minerals
The human body requires various minerals for a wide variety of metabolic functions. Calcium,
phosphorus, magnesium, iron, and the electrolytes sodium, potassium, and chloride are called
the major minerals. The importance of minerals for bone health, oxygen-carrying capacity, and
fluid and electrolyte balance is well recognized; with iron and calcium receiving special
attention by athletic populations. Athletes who do not consume enough dietary iron risk iron
depletion and impaired performance. Inadequate dietary calcium can contribute to low bone
density and risk for fracture.
Iron
Iron makes up part of hemoglobin and myoglobin in the blood which play a role in oxygen
transport and utilization of energy. Iron deficiency reduces athletic performance. Spinach,
clams, cereal, oysters, meat, and soybeans are rich in iron.
Calcium
Athletes who consume a low-calcium diet may be at risk for osteoporosis, a deterioration of the
bone tissue that leads to an increased risk of fracture. Milk, cheese, and yogurt are high in
calcium.
FLUID AND ELECTROLYTES
Water and electrolytes play a critical role in keeping your body from overheating during
exercise. Dehydration not only affects performance, but in serious cases causes heat related
illness (heat stroke) or even death.
Water
Water is the largest component of the body, representing 45 to 75% of a person’s body weight.
Water affects athletic performance more than any other nutrient. Consuming fluids in sufficient
amounts is essential for normal cellular function and, of particular importance to athletes, heat
dissipation. The recommended intake for water is 3.0L/day (100 oz., 13 cups) for men and
2.7L/day (74 oz., 9 cups) for women. Athletes sweating profusely for several hours per day may
need to consume an extra 3 to 4 gallons (11-15 L) of fluid to replace losses.
Fluid loss equal to as little as 1% of body weight can be associated with an elevation in core
temperature during exercise. Fluid loss of 3% to 5% of body weight results in cardiovascular
strain and impaired ability to dissipate heat. At 7% loss, collapse is likely.
In order to monitor hydration status an athlete should take his/her weight before and after a
workout. Each pound lost during the workout represents 1 pint (0.5L) of fluid loss that needs to
be replaced before the next training session. Water weight loss is not healthy weight loss!
Electrolytes
Electrolytes play an important role in the regulation of water distribution in the body. Sodium
plays a major role in fluid regulation while potassium, chloride, and magnesium are essential to
muscular contraction and nerve conduction. Deficiencies in electrolytes hinder athletic
performance. Recommended daily sodium intake is 4 to 6g/day. This level is normally sufficient
to replace sodium lost through sweat, although athletes who sweat profusely or exercise in hot
environments may need higher levels of sodium. Daily potassium intake of 2 to 6g/day is
sufficient to replace levels lost in sweat.
Fluid Replacement
Fluid replacement occurs in three general times: before activity, during activity, and after
activity. The goal is to begin exercise in a hydrated state, avoid dehydration during exercise, and
rehydrate before the next training session. See table 1.3 for general fluid replacement
guidelines.
Table 1.3: Fluid Replacement Guidelines
Before a Training Session
 Must be properly hydrated before prolonged exercise in a hot environment.
 Intake should be approximately 16 ounces (0.5 L) 2 hours before a workout.
During a Training Session
 Have cool fluids readily available (water or sports drink)
o Sports drink or 50/50 mix of sports drink and water is recommended for exercise
in hot conditions to ensure adequate electrolyte levels
 Athletes should drink frequently – 6 to 8 ounces of fluid every 15 minutes.
After a Training Session
 Athletes should replenish fluids with at least 1 pint (0.5 L) for every pound of body
weight loss
 The ideal replacement beverage is dependent on the duration and intensity of exercise,
environmental temperature, and the athlete.
o Sports drink or 50/50 mix of sports drink and water is recommended after
profuse sweating or exercise in extreme heat to ensure proper replacement of
electrolytes.
*Adopted from Esssentials of Strength Training and Conditioning by the National Strength and Conditioning Association. (2005).
REFERENCE
Information and charts in this article are adopted from Esssentials of Strength Training and
Conditioning by Thomas Baechle and Roger Earle. http://www.nsca-lift.org