March 2008 Issue

Sports Nutrition for Young Athletes: Vital to Victory
By Pamela M. Nisevich, MS, RD, LD
Today’s Dietitian
Vol. 10 No. 3 P. 44

By analyzing their diets and coaching them on the most valuable nutrients, RDs can help their young athletic clients play to the best of their competitive ability.

A young athlete enters an RD’s office and turns in his three-day food record. He’s proud of himself for “improving” his diet, but as the RD reviews his intake, she grows increasingly disturbed. The athlete fuels at breakfast with two Super Donuts; regardless of the touted extra protein, vitamins, and minerals, he’s not off to a good start. The RD is equally unimpressed with his lunch choices: a deli sandwich on white bread with three packets of mayonnaise, a 16-ounce juice, a small bag of potato chips, and a 6-ounce blueberry muffin. Ten minutes before a big game, he downs 12 ounces of Coke and a chocolate chip cookie and, more than three hours after the final whistle, finally recovers with a foot-long cheesesteak and large order of fries.

After reviewing his intake, the RD wonders how to break it to this young man with “improved nutrition” that there is nothing super about donuts, blueberry muffins do not count as a fruit serving, and fries are not a vegetable. But before criticizing him for his precompetition meal of high-fructose corn syrup and fat, she remembers having the same poor eating habits when she was a young athlete, constantly on the run and at the mercy of whatever the school vending machine and cafeteria offered.

Sports Nutrition: Critical to Success
All athletes strive to compete at the top of their game but, unbeknownst to many of them, their performance relies on their nutritional status. Jenna A. Bell-Wilson, PhD, RD, CSSD, who is a certified specialist in sports dietetics in Arlington, Mass., says that young athletes with inadequate diets may have insufficient fuel for workouts, nutrient deficiencies that can lead to illness or fatigue, a decrement in bone growth and maintenance, and may not reach their potential for muscle growth. All of these will be reflected in their performance, regardless of their determination.

Despite the recognition that young athletes need to pay greater attention to their fuel consumption, recent research suggests that many youths struggle with energy balance, experiencing an energy deficit or surplus. We are all too familiar with this energy surplus, known as overweight or obesity—but that crisis is not the focus of this article. The concern is that many young athletes require greater amounts of nutrients but remain uninformed or unconcerned about their nutrition needs or simply feel powerless to improve their nutritional status. RDs can help young athletes overcome these problems.

The number of young athletes in the United States is increasing and estimates are that approximately 30 to 45 million youths aged 6 to 18 participate in some form of athletics.1 These young athletes turn to coaches, parents, teammates, and health professionals for nutrition guidance. RDs, especially those who are certified specialists in sports dietetics, guide athletes to be leaner, stronger, and able to withstand the rigors of training and competition. RDs can offer superior advice because they are more cognizant of research findings and are equipped with clinical and counseling skills to aid in a young athlete’s quest for improvement. By helping athletes improve their diet, RDs can eliminate obstacles to better health and nutrition and thereby help athletes push their limits and reach their full potential.

Nutrition professionals can aid young athletes in their quest for victory by recognizing that children and adolescents generally need more calories and protein per pound of body weight than many adults. It is a well-known fact that children need this extra energy to grow, fully develop, and thrive. Nutrient needs further elevate and reach their peak during adolescence.2 Potential differences in nutrition needs between a typical child or adolescent and an athletic child or adolescent likely exist but are not entirely clear. Limited studies of energy balance in young athletes have been published, and conservative recommendations have been made. But self-reported diet records of young athletes often indicate that intake of energy, carbohydrate, and select micronutrients may be below recommended levels. RDs must be aware that these deficiencies exist and are especially apparent in athletes involved in sports that focus on body composition and appearance.3

Proper Intake of Macronutrients and Micronutrients

Critical Micronutrients
Current research and trends point to deficiencies in calcium, iron, folate, vitamin B6, and zinc for young athletes. The functions, risks of deficiency, and recommendations for each vital micronutrient follow.

Calcium
Proper intake of calcium is needed to support bone growth, increase bone mass, and aid in nerve impulses and muscle contraction.4 Poor calcium intake can lead to decreased bone mass and consequential increased risk for stress fractures and other bone-related injuries.1 Because a young athlete’s growing bones cannot handle as much stress as an adult’s mature bones, optimum bone health is critical; overuse and overtraining injuries are more apt to occur in a pediatric or adolescent athlete. To ensure proper bone health, keep in mind that the adequate intake of calcium for children aged 9 to 18 is 1,300 milligrams per day.5

Iron
While iron is noted for its oxygen-carrying capacity, it is also a major player in the energy metabolism of carbohydrate, protein, and fats. For this reason, young athletes with iron-deficiency anemia may experience performance inhibition ranging from decreased work capacity to extreme fatigue, impaired immune function, and impaired cognitive reasoning. Because iron deficiency is one of the most common nutrient deficiencies in the world, it is imperative that professionals working with young athletes are aware of the athlete’s iron intake.

On the other hand, it is important to note that iron toxicity is the most common cause of poisoning death in young children. If you want to avoid recommending a supplement, you can recommend food items that are high in iron, such as red meat and enriched cereals and grains, coupled with fruits and vegetables that are high in vitamin C, which aids in iron absorption.

B Vitamins
Both vitamin B6 (pyridoxine) and folate are members of the B-complex of vitamins and are critical components of energy metabolism and blood health.4 Both are critical for amino acid metabolism and good sources of each are enriched grain products and assorted animal products. Research differs on whether there are changes in folate and vitamin B6 levels during periods of heavy training. However, the conclusion is usually that exercise does not increase the requirements for these nutrients and the dietary reference intake should be followed.6 In general, a B-complex deficiency can lead to fatigue, muscle soreness, apathy, and loss of cognitive function.

Zinc
While an extreme zinc deficiency is uncommon in the United States, athletes are at risk due to poor consumption of foods rich in this mineral. Zinc plays a role in more than 300 enzymatic reactions in the body and is critical for wound healing, tissue growth and maintenance, and immune function. Various studies have shown that zinc status directly affects basal metabolic rate, thyroid hormone levels, and protein utilization; thus, zinc is critical to athletes. Dietary protein enhances zinc absorption, and athletes who are most at risk of a deficiency may be vegetarians or those who primarily eat a grain-based diet. With the myriad critical functions to which zinc is linked, consumption of adequate levels of zinc should be stressed.6

Critical Macronutrients
With an increase in energy expenditure comes a subsequent need for an increase in the intake of carbohydrate, protein, and fat. Current research and trends point to deficiencies in overall total energy and carbohydrate intake. Also of concern is deficient fluid intake and consequent altered hydration status of young athletes. The functions, risks of deficiency, and recommendations for each vital macronutrient follows.

Carbohydrate
In athletes, poor carbohydrate intake results in inadequate glycogen stores and premature fatigue, which not only compromises performance but also forces the body to rely on another source for fuel: protein. Glucose from carbohydrate sources is essential to most body functions during exercise. If glucose is not available for use as fuel during physical activity, the body will take from its protein stores for energy via gluconeogenesis. Because carbohydrate is the preferred fuel for athletic performance, approximately 55% of total daily calories should come from carbohydrate. The young athlete has the capacity to store carbohydrate in the form of glycogen, but this capacity is limited, so carbohydrate must be consumed daily. Carbohydrate needs are based on body weight and intensity of activity. The American Dietetic Association (ADA) has set the following recommendations for the young athlete:

• 3 to 5 grams of carbohydrate per kilogram for very light intensity training;

• 5 to 8 grams of carbohydrate per kilogram for moderate or heavy training;

• 8 to 9 grams of carbohydrate per kilogram for preevent loading (24 to 48 hours prior); and

• 1.7 grams of carbohydrate per kilogram for postevent refueling (within two to three hours).7

Protein
Protein is an essential part of the young athlete’s diet, and the role of protein for youth includes building, maintaining, and repairing muscle and other body tissues.7 It should be noted that an adequate protein intake with inadequate caloric intake prohibits protein balance, even when the recommended daily allowance for protein is consumed.8 Therefore, it is critical that young athletes consume enough calories to maintain body weight.

While adult endurance and strength athletes may need more protein per pound of body weight, additional protein needs for young athletes have not been specifically evaluated. However, the ADA has set the following recommendations:

• Athletes who have just begun a training program require 1 to 1.5 grams per kilogram per day of protein.

• Athletes participating in endurance sports require 1.2 to 1.4 grams per kilogram per day of protein.

• Athletes who restrict calories must be certain to consume adequate protein for muscle building and repair. A minimum of 1.4 grams per kilogram per day is recommended.
• Vegetarian and vegan athletes should be counseled to ensure that adequate intake of protein is consumed from plant sources.

• Consuming an overabundance of protein can lead to dehydration, weight gain, and increased calcium loss. This is critical to monitor as research shows that the population of young athletes is already at risk for calcium deficiency.7

Fat
While carbohydrate is often spotlighted as the preferred fuel for sports, there are some bodies of research suggesting that lipid or fat may be the preferred fuel for children. This may be due to the higher rate of fat oxidation in children.9 As a major energy source, fat is essential for light- to moderate-intensity exercise and for endurance exercise. Below are some easy-to-follow guidelines for consumption of fats:

• While a low-fat diet can be followed, it is important that young athletes consume an average of 20% to 30% of calories from fat.

• Like adults, young athletes should aim to significantly lower the amount of saturated and trans fat in their diet. The focus should be on an intake of healthy fat from plant oils and soft margarines made with vegetable oils and on limiting the amounts of fried and processed foods.

Fluid
Maintaining fluid balance is critical for the young athlete. As rates of youth participation in endurance events climb, legitimate concerns about fluid status have arisen. Aside from the risk of heat-related illness, dehydration is strongly associated with fatigue during exercise. This risk is increased in certain environmental conditions such as high heat and humidity.

Compared with adults, young athletes may be at a higher risk for altered fluid status for several reasons: Children experience greater heat stress and heat accumulation, and they have a greater ratio of surface area to body mass and absorb heat more readily.10 Signs of dehydration in children include dark urine, small urine volume, muscle cramps, reduced sweating, increased heart rate, headaches, and nausea. Specific recommendations for fluid consumption are as follows:

• Child and adolescent athletes should aim to replenish lost hydration stores during and after an event. This can be done by weighing the athlete before and after an event and replacing fluids lost (16 to 24 ounces for every pound lost).7

• For activities lasting less than 60 minutes, select water for hydration.

• For activities lasting more than 60 minutes, select sports beverages for hydration, electrolytes, and energy from carbohydrate. Select a beverage that provides 6% to 8% carbohydrate.

• Lastly, be aware that children do not instinctively drink enough fluids to replace lost stores and thirst does not always indicate when the body is in need of more fluids.

Overcoming Nutritional Obstacles
While young athletes rely on their parents and health professionals for advice, they are extremely susceptible to peer and media influence and the plethora of misinformation that exists in the sports nutrition world.8 As a result, obstacles to improving the nutritional status and consequent performance of the young athlete abound.

Kelly White, MS, RD, LD, a sports nutrition and wellness dietitian in Starkville, Miss., notes that young athletes often struggle with inadequate nutrition-based knowledge, lack of healthy food options, and making the “right” food choices. She suggests that athletes and their parents plan ahead and pack lunches and fueling snacks. Good choices include whole grain granola bars and sandwiches, fresh fruit and vegetables, water, and Gatorade. White suggests that RDs become familiar with the food items offered in school cafeterias and vending machines so athletes will have a better idea of what to select.

Taking into account all the obstacles and elevated nutritional needs that young athletes face, the RD mentioned at the beginning of this article approaches the nutritional status of her young client not with an air of condescension but concern. She knows that he made the right choice by asking her for assistance with his diet and performance. As a nutrition professional, she realizes it is her job to help this young athlete understand that to meet the demands of his sport and the physiological needs of his developing body, it is critical that he not deprive himself of macronutrients and micronutrients. Thus, her first goal is to provide simple tips to improve his day-to-day, game-to-game intake. Her final goal is to impress upon him that it is never to early or too late to make nutrition a top priority.

— Pamela M. Nisevich, MS, RD, LD, is a consultant for Nutrition for the Long Run in Dayton, Ohio. She specializes in writing, counseling, and speaking on sports nutrition, weight management, and wellness. She is also a pediatric clinical dietitian at Dayton Children’s Medical Center and the director of The Body Shop, a weight management program for overweight and obese children.

References
1. Brenner JS, American Academy of Pediatrics Council on Sports Medicine and Fitness. Overuse injuries, overtraining, and burnout in child and adolescent athletes. Pediatrics. 2007;119:1242-1245.

2. Croll JK, Neumark-Sztainer D, Story M, et al. Adolescents involved in weight-related and power team sports have better eating patterns and nutrient intakes than non-sport-involved adolescents. J Am Diet Assoc. 2006;106:709-717.

3. Kern M. Dietary intake of adolescent athletes and nonathletes. J Am Diet Assoc. 2006;106:717-718.

4. Thompson J, Manore M. Nutrition: An Applied Approach. San Francisco: Benjamin Cummings; 2006.

5. Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals, Vitamins. Food Nutrition Board, Institute of Medicine, National Academies, 2004. Available here. Accessed December 31, 2007.

6. Sports Cardiovascular and Wellness Nutritionists, Dunford M. Sports Nutrition: a Practice Manual for Professionals, 4th edition. Chicago, Ill: American Dietetic Association; 2006.

7. Spear BA. Nutrition management of the child athlete. In: Nevin-Folino NL (ed). Pediatric Manual of Clinical Dietetics, 2nd edition. Chicago, Ill: American Dietetic Association; 2003.

8. Thompson JL. Energy balance in young athletes. Int J Sport Nutr. 1998;8(2):160-174

9. Montfort-Steiger V, Williams CA. Carbohydrate intake considerations for young athletes. J Sports Sci Med. 2007;6:343-352.

10. Petrie HJ, Stover EA, Horswill CA. Nutritional concerns for the child and adolescent competitor. Nutrition. 2004;20:620-631.