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Sports Nutrition for the Adolescent Athlete

George B. Batten, M.D.

Adequate nutrition is important for the proper growth and development of young people.  It is even more essential to the competitive youth athlete.  With the higher demands of strenuous training and competition, proper diet is crucial to not only insure optimal performance, but also to prevent developmental problems, which may have lifelong effects.  Young women athletes in particular have special needs and requirements in regard to nutrition, which must be carefully monitored.

— NUTRITIONAL BASICS

Proper nutrition is a combination of adequate caloric intake, obtained through the correct percentages of the basic energy sources (carbohydrates, protein, and fat), available and consumed in the major food groups, and supplemented when necessary by additional vitamins and minerals.

A. ADEQUATE CALORIC INTAKE

Rapid growth and high nutritional demands characterize adolescence.  Daily caloric requirements are dependent upon rate of growth, age, gender, weight, and energy demands of specific sport.

Estimated Average Calories for Adolescents (per kg. of body weight)*

Age Calories (per kg.) Calories (per day)
11-14 yr. (F) 47 2200
11-14 yr (M) 55 2500
15-18 yr. (F) 40 2200
15-18 yr (M) 45 3000

*Doesn’t include additional calories required by sports participation
**1 kg. = 2.2 lbs.  A 100-lb. athlete weighs approximately 44 kg. (100/2.2=44.4)

Caloric Demands of Soccer
(Calories per 10 minutes)

Body Weight (in kg.) 30 kg. 40 kg. 50 kg. 60 kg.
Calories 54 72 90 108

EXAMPLE:  A 100 lb. (44 kg.) 12 year old female soccer player who participates in a one hour game should be consuming 2554 calories per day.

Basic calories: 47 cal x 44 kg. = 2068
Sports calories: 81 cal x 6 =  486

2554 cal per day*

*Don’t forget to include practice time and multiple games per day..

B. ENERGY SOURCES

The type and quantity of energy sources depends upon the intensity and duration of activity.
Glucose is the basic sugar (carbohydrate) utilized by the body for energy and growth.  It is stored in the form of glycogen in tissues such as muscle and the liver.  It is the initial energy source used for fuel.  When its storage capacity is depleted, the body turns to fat and protein for additional energy.  These last two sources are not as quickly or easily utilized as glucose, however.  Therefore, the key to sports nutrition is carbohydrates.  They are the cornerstone of an athlete’s diet.

The current recommended Training Diet for an adolescent athlete is:

  • 55-60% Carbohydrates
  • 25-30% Fat
  • 12-15% Protein

***CARBOHYDRATES

Carbohydrate consumption needs to be considered in both pre-training and post-training meals.  Carbohydrates are easily and rapidly digested.   Prior to training and competition, it is important to have glucose available in stored glycogen to use as energy.  After sports it must be replaced in preparation for the next training or competition.  Consuming high carbohydrate fluids and foods immediately after exercise increases muscle glycogen storage and improves recovery time.

Adolescents generally need 6-8 grams of carbohydrates per kg. body weight per day.  Good sources include breads, cereals, rice, pasta, dairy products, fruits, and vegetables.

***FATS

After using its glycogen stores (carbohydrates), the body turns to fat for additional energy.  However, its ability to do this decreases with prolonged exercise.  Eating too much fat, also, decreases the percentage intake of carbohydrates, fiber, and other essential nutrients. Fats delay gastric emptying and may result in bloated, sluggish feeling if consumed too close to exercising.

***PROTEIN

May contribute 10% of exercise energy when glycogen depleted.  Its percentage is also increased when caloric intake is decreased.  Protein consumption should be in the range of 1.2-1.4 grams per kg. per day.

Protein supplements have not been shown to enhance muscle development, strength, or endurance in young athletes.  Excess protein is merely burned as fuel or converted to fat.  High protein is often high fat as well.

Vegetarians need to be careful in making sure that they are receiving adequate protein in their diets.  It is easy for them to fall behind in total daily calories, protein, and nutrients, such as, calcium, Vitamins D& B12, zinc, and iron.  Food sources rich in protein include meats fish, eggs, nuts, dairy products, and certain vegetables, such as, peas and beans.

C. FOOD GROUPS

In order to consume the necessary energy sources, it is recommended that a well balanced diet, drawing from each of the major food groups, be planned for the growing athlete.

A sample diet might include:

Bread, cereal, rice, pasta group 6-11 servings per day
Vegetable group 3-5 servings per day
Fruit group 2-4 servings per day
Dairy group 2-3 servings per day
Meat, poultry, fish group 2-3 servings per day

D. VITAMINS & MINERALS

Supplemental vitamins and minerals may improve the nutritional status of individuals with deficiencies, often the result of dietary inadequacies.  However, no scientific data supports the general use of supplements to improve athletic performance.  Especially in young athletes, the unsupervised, indiscriminate use of supplements raises health concerns.

Female adolescent athletes do, however, have to be concerned about the intake of adequate calcium and iron.  The problem of anemia and osteoporosis are well-recognized in highly competitive female athletes.  The nutritional requirements of calcium and iron are higher in females.  In addition, their intake may be inadequate due to reduced meat and dairy consumption by the female athlete attempting to decrease fat and eat “healthy”.  In females, 48% of adult bone density is established during adolescence.

While it is generally advisable to encourage the adequate dietary intake of these nutrients over supplementation, the daily use of a multi-vitamin and additional calcium seems reasonable.  Good dietary sources include red meats, fortified cereals, dried fruit, and calcium fortified orange juice.

*Recommendation:

  • Multi-vitamin (not “mega dose”) with RDA 15mg Iron
  • 500-600 mg Calcium (Extra Strength Tums=600mg.) 

E. FLUIDS

It is important to remember that young athletes do not tolerate temperature extremes as well as adults.  They produce less sweat and generate more heat.  Remember that dehydration occurs prior to the onset of increased thirst. Ultimately, easy fatigue, irritability, and a sudden decrease in performance result.  More serious medical complications, such as, heat exhaustion and potentially fatal heat stroke follow.

Prevention is the key to avoiding the health problems associated with fluid replacement.

  • Encourage fluid consumption even in the absence of thirst
  • Frequent water breaks every 15-20 minutes
  • Adequate hydration in the days prior to training/competition
  • At least one cup of water per 20 minute, more in extreme heat

Water is probably best for fluid replacement during competition.  Sports drinks after exercise are helpful in providing carbohydrates.  Avoid salty and carbonated drinks.

— PRE-COMPETITION EATING

Using these principles and guidelines, it should be possible to construct a proper diet to be utilized by the young athlete prior to training and competition.  Ideally, it is desirable to avoid hunger during the upcoming event and provide additional fuel.  The food should be easily digested and quickly emptied from the stomach (high in carbohydrates, low in fat and protein).  It is best to consume a high carbohydrate meal 1-4 hours prior to competition.  To avoid GI distress, reduce the size of the meal the closer you get to competition.  Avoid fatty foods and high protein foods.  They delay gastric emptying and contribute to that sluggish, heavy feeling.  Avoid extremely salty foods as they cause fluid retention and that bloated feeling. Don’t forget fluid loading!

1-2 HOURS BEFORE

Fruit or vegetable juices,  sports drinks

Fresh fruit

2-3 HOURS BEFORE

Fruit or vegetable juices,  sports drinks

Fresh fruit

Breads, bagels, crackers, English muffins

3 OR MORE HOURS BEFORE

Fruit or vegetable juices,  sports drinks

Fresh fruit

Breads, bagels, crackers, English muffins

Peanut butter, lean meat, low fat cheese

Low-fat yogurt

Pasta with tomato sauce

Cereal with low-fat milk

— POST-COMPETITION EATING

The goal is to increase muscle glycogen and recovery time, utilizing high carbohydrate fluids and food.  Should be easily digested.  Guideline is 1.5 grams of carbohydrate per kg. body weight, 30 minutes after training/competition, followed by additional 1.5 grams per kg., 2 hours later.  May supplement with high carbohydrate beverages (Gatorade), but these should not be used to replace regular food.

 

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