Why nutrient deficiencies can spell defeat for kids who compete in sports.
More and more young athletes are seeking personal fitness trainers for specialized workouts. As part of their training, we strive to help these young people become stronger and better able to withstand the rigors of sports competition. But physical training is only one part of the equation: young athletes also need to learn why proper nutrition is vital to optimizing their sports performance.
Nutrient needs are higher during adolescence than at any other time in the life cycle (Croll et al. 2006). Even kids not engaged in sports need the proper mix of calories, carbohydrates, healthy fats and protein. Among young athletes, many are deficient in some of the key nutrients that should be fueling their workouts.
Although it is outside your scope of practice as a fitness professional to make specific dietary recommendations, you can educate young athletes about sound nutrition choices that will help them win—both on and off the field.
How Nutrition Affects Kids’ Performance
While proper nutrition is important for all athletes, it is of particular concern for young, growing bodies that compete in sports. IDEA contributing editor Jenna A. Bell-Wilson, PhD, RD, is a certified specialist in sports dietetics who is based in Arlington, Massachusetts. She says that an inadequate diet can result in a young athlete getting insufficient fuel for workouts; having deficiencies that can lead to illness or fatigue; suffering a decrement in bone growth and maintenance; and not achieving proper muscle growth. According to Bell-Wilson, nutrient deficiencies will negatively affect the youngster’s growth and his or her ability to compete in a chosen sport.
Maintaining the appropriate balance between energy and protein intake is critical for the growth and development of young athletes. Despite the recent public attention given to the benefits of healthy eating, many young athletes remain undernourished (and undereducated!). Self-reported dietary intakes often reveal that an increasing number of children have energy, carbohydrate and certain micronutrient intakes below the recommended daily levels. In particular, athletes in sports that focus on body composition and appearance (e.g., gymnastics and distance running) are often deficient in several key nutrients (Kern 2006).
Common Nutrient Deficiencies
The nutrients in which young athletes are most often deficient are carbohydrates, calcium, vitamin B6, folate and iron (Kern 2006; Thompson 1998).
A deficiency in carbohydrates leads to inadequate glycogen stores and premature fatigue, both of which compromise performance and force the body to rely on an alternative source of fuel. Glucose is essential to body functioning during exercise. If glucose from carbohydrate is not available for use as fuel during physical activity, the body will instead use protein (muscle) stores for energy. However, the body would much rather use carbohydrate or fat for fuel.
Proper intake of calcium is needed to support bone growth, increase bone mass and aid in nerve impulses and muscle contraction (Thompson & Manore 2006). Inadequate calcium intake can lead to decreased bone mass, which can increase the risk for stress fractures and other bone-related injuries.
Both vitamin B6 and folate are critical components of energy metabolism and blood health (Thompson & Manore 2006). Both these nutrients are vital for amino acid metabolism (think “the building blocks of proteins”). A deficiency in vitamin B6 and folate can lead to fatigue, muscle soreness, apathy and loss of cognitive function for an athlete.
While iron is vital for oxygen-carrying capacity, it is also a major player in the energy metabolism of carbohydrates, protein and fats. This is why young athletes who are deficient in iron (i.e., have iron-deficiency anemia) may experience fatigue, compromised immune function and impaired cognitive reasoning during exercise. Iron intake is especially critical for prepubertal and menstruating female athletes.
Although iron deficiency is a worldwide problem, there is such a thing as too much iron. Young athletes who take iron supplements can build up toxic levels of this mineral. That’s why iron supplement recommendations should always come from a physician or a registered dietitian (RD).
Fluid & Macronutrient Needs
Giving specific dietary advice to young athletes is beyond your scope of practice, but you can promote healthful eating behaviors and energy-rich foods that are in accordance with recommendations established by nutrition professionals. Here are some guidelines for young athletes that are culled from recently published scientific research.
Maintaining the proper fluid balance is critical for this population. In addition to the risk of causing a heat-related illness, dehydration can lead to fatigue during exercise. Altered fluid status can be a bigger risk for kids than for adult athletes for two reasons: (1) children experience greater heat stress and heat accumulation during exercise; and (2) children have a greater ratio of surface area to body mass and absorb heat more readily than do adults (Petrie, Stover & Horswill 2004).
Signs of dehydration in children include, but are not limited to, the following:
- dark urine
- small volume of urine
- muscle cramps
- reduced sweating
- increased heart rate
Child and adolescent athletes should replenish lost hydration stores during and after a competition or a heavy workout. Weighing an athlete before and after an exercise bout allows you to gauge how much fluid needs replacing; the general rule of thumb is 16–24 ounces of liquid for every pound lost (Nevin-Folino 2003). Be aware that children do not instinctively drink enough fluids to replace lost stores, and thirst does not always indicate when the body needs more fluids.
During activities lasting less than 60 minutes, water is all that is needed to hydrate young athletes. However, during longer activities, sports beverages that provide 6%–8% carbohydrate will help rehydrate and replenish electrolyte stores in young athletes. It helps that kids like the flavoring of sports beverages, which means they will drink more of them without prodding (Nevin-Folino 2003).
Since carbohydrates are the preferred fuel for athletic performance, approximately 55% of a young athlete’s total daily calories should come from carbohydrate (Nevin-Folino 2003). Carbohydrate needs are based on body weight and intensity of activity. The American Dietetic Association (ADA) has set the following daily recommendations for young athletes (Nevin-Folino 2003):
- 3–5 grams (g) carbohydrates per kilogram (carb/kg) for very light intensity training
- 5–8 g carb/kg for moderate or heavy training
- 8–9 g carb/kg for pre-event loading (24–48 hours prior)
- 1.7 g carb/kg for postevent refueling (within 2–3 hours)
An essential part of a young athlete’s diet, protein is responsible for building, maintaining and repairing muscle and other body tissue (Nevin-Folino 2003). It should be noted that inadequate caloric intake will cause a protein imbalance even if the athlete consumes the recommended daily allowance (RDA) of protein (Thompson 1998). Young athletes need to consume enough calories each day to maintain body weight and keep protein stores in balance.
While it has been suggested that adult athletes may need more protein per pound of body weight than adults who are not athletes, additional protein needs have not been specifically evaluated for younger athletes. However, the ADA has issued the following daily recommendations (Nevin-Folino 2003):
- Athletes who have just begun a training program require 1.0–1.5 g/kg of protein.
- Athletes who participate in endurance sports require 1.2–1.4 g/kg.
- Vegetarian and vegan athletes should be counseled to ensure that adequate intake or protein is consumed from plant sources.
- Athletes need to consume sufficient calories each day to maintain protein balance.
A word of caution: consuming an overabundance of protein can lead to dehydration, weight gain and calcium loss. It is critical that young athletes monitor their daily protein intake, because this population is already at risk for calcium deficiency.
Fat is an essential fuel for young athletes who engage in light- to moderate-intensity exercise or in endurance events. Although carbohydrates are the preferred fuel for adult athletes, healthy fats may be a better choice for children who engage in sports (Montfort-Steiger & Williams 2007). This could be due to the higher rate at which fat oxidizes in the young body; the faster the fat is broken down, the quicker it can be used as fuel for exercise (Montfort-Steiger & Williams 2007). Keep in mind, however, that kids who compete are usually trying to build muscle mass and may not want to add any fat to their diet. Teach them that healthy fats are a far better choice than butter, animal fat or lard.
Below are some easy-to-follow guidelines for young athletes on daily consumption of fats:
- It is important that young athletes obtain an average of 20%–30% of their calories from fat; clients can achieve this even with low-fat foods (but not nonfat) (Nevin-Folino 2003).
- Young athletes should aim to significantly lower the amount of saturated and trans fat in their diet.
- The best choices for young athletes are healthy fats from plant oils (e.g., canola or olive oil); these clients should limit their intake of unhealthy saturated fats found in fried and processed foods.
Kids Will Be Kids
Young athletes are often grossly misinformed about sports nutrition practices and very easily influenced by outsiders, especially their peers. They also rely heavily on the Internet and other media for information (Thompson 1998). Another obstacle that young athletes face is finding the time to fuel their bodies properly. With the rigors of school, work, practice and competition, time and access to quality nutrition are often limited.
While some athletes need only a few dietary tweaks, others require great care to improve their nutrition and subsequent performance. That’s when it is best to employ the help of an RD who is an expert in sports dietetics or sports nutrition. Look for an RD who is credentialed as a certified specialist in sports dietetics (CSSD). You can find a local sports dietitian through the ADA’s practice group, SCAN, at www.scandpg.org/mapsearch.php.
As a fitness professional, you can and should help young athletes understand the role that proper nutrition plays in sports performance. Kids need to know exactly why it is essential that they fuel their bodies with the nutrients and fluids that will help them succeed in their chosen sports. It is critical that all athletes—young and old—make nutrition a top priority if they want to win at sports and life.
SIDEBAR: Adequate Intakes of Commonly Deficient Micronutrients
The following recommendations for children and adolescents are in accordance with those set by the Institute of Medicine National Academies Food and Nutrition Board (2004):
Pamela M. Nisevich, MS, RD, LD, is a clinical dietitian at Dayton Children’s Medical Center in Ohio, where she specializes in pediatric clinical nutrition. She is the founder and owner of Nutrition for the Long Run, a counseling firm that focuses on sports nutrition and weight management for athletes of all ages.References
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Food and Nutrition Board. 2004. Dietary Reference Intakes (DRIs): Recommended intakes for individuals, vitamins. www.iom.edu/Object.File/Master/21/372/0.pdf; retrieved Dec. 31, 2007.
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Montfort-Steiger, V., & Williams, C.A. 2007. Carbohydrate intake considerations for young athletes. Journal of Sports Science and Medicine, 6, 343–52.
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