Performance Nutrition for the Adolescent Athlete: A Realistic Approach

The goal of sports nutrition is to help an athlete optimize performance potential and overall health. For adolescent athletes, the top priority is healthy growth, development, and maturation. In practice, this means assessing nutrition to ensure growth and development is not negatively affected when intense training is combined with poor nutrition.1 The sports physician can assess food habits, timing, and amounts of foods and fluids to give helpful tips during the visit. Physicians can also be the first line of defense for dispelling myths about fad diets. Referral to a registered dietitian can be made for a more comprehensive nutrition assessment. FOOD SELECTION AND HABITS Adolescent athletes have a wide range of nutritional needs based on body size, training intensity, age, and sex. Some factors that influence the food choices of adolescents are convenience, cravings, time, peer/parental influence, cost, and food preparation skills.1 For busy teens and working parents, food that is easy to access and carry without much preparation time is appealing. Adolescents tend to depend on snacking because they balance school schedules during the day with training before or after school. Knowing how to choose healthy snacks and having access to healthy options is important for this population. NUTRITION ASSESSMENT Collecting a quick diet history can help identify specific eating patterns and raise “red flags” to anything that may need to be addressed in more detail (ie inconsistent eating patterns, disordered eating, lack of food groups, etc.). Food group quantity checklists or 24-hour recall methods are more useful than food logs for providing a snapshot into eating habits, especially if time is limited. Refer to Figures 1 and 2 for templates for daily and weekly food group frequency charts, respectively. It is important to keep in mind that eating habits and patterns can change drastically from training to competition days and from weekdays to weekends.Figure 1.: Daily food group frequency template.Figure 2.: Weekly food group frequency template.Collecting a diet history can also help gauge eating times and identify missed eating opportunities during the day. Helping an athlete plan eating opportunities during his/her scheduled day can be beneficial to ensure energy needs are met. It can also be used as a planning tool to guide food selection. See Figure 3 for a sample planning tool.Figure 3.: Planning tool for eating opportunities around workouts and during the day.ENERGY RECOMMENDATIONS As stated previously, consuming enough calories to maintain a healthy body weight and keep up with growth/maturation standards should take precedence with performance and training goals coming in second. Energy is usually in deficit or surplus in adolescents, rarely is energy balance seen.1 That being said, research on energy balance for adolescent athletes is limited. There are not specific nutrition and energy recommendations for the adolescent athlete. Currently, young athlete nutritional recommendations are based on the energy calculations of adult athletes and dietary reference intakes for age and sex for micronutrients.1 Estimates of average time and intensity of training are needed to calculate energy expenditure in addition to energy needed for appropriate growth. The United States Department of Agriculture MyPlate website provides an easy way for athletes to estimate energy requirements: https://www.choosemyplate.gov/MyPlatePlan.2 Athletes who desire more precision may want to consider a referral to a sports dietitian for an assessment using the Cunningham or the Harris–Benedict equations with an appropriate activity factor to estimated energy expenditure.3–5 Although these equations are included in the 2016 joint position statement “Nutrition and Athletic Performance” by the American College of Sports Medicine, it should be noted that the specific nutritional needs of child and adolescent athletes are not addressed in the statement.3 Measures of growth, development, and physiological function should be used to make sure energy intake in meeting the individual's needs.6 MACRONUTRIENTS Like energy balance, evidence-based recommendations of carbohydrate, protein, and fat intake for the active adolescent are nearly nonexistent. Refer to Table 1 for general macronutrient recommendations for athletes.3 Again, suggested intake is based on adult athlete recommendations.TABLE 1.: General Macronutrient Recommendations for Athletes3Figure 4.: Pre-exercise: 2 to 4 hours before nutritional goals and guidelines.CARBOHYDRATE Carbohydrates are the main source of energy for the body, muscles, and brain. Carbohydrate should provide most of the increased calorie needs of a young athlete.7 Not having enough carbohydrate in the diet can cause early fatigue, and the body can start to break down muscle for energy. Young athletes also store less glycogen than adults, which may cause them to experience fatigue faster.7 Carbohydrate foods cannot seem to get rid of the stigma that carbohydrates cause weight gain or are unhealthy. Low carbohydrate consumption in athletes, no matter what age, can cause poor energy levels because of depletion of glycogen stores.3 Dehydration and cramping is also a concern with low carbohydrate intake because carbohydrates store water in the muscle. It is important to help an adolescent athlete recognize the importance of carbohydrates as an energy source for improved performance and overall health. Priority should be placed on selecting healthy carbohydrate sources around/during training periods, then working on specific amounts. It is a common misconception that carbohydrates only come from grains. Fruit, milk, yogurt, and starchy vegetables (legumes, potatoes, winter squash, etc.) also are sources of carbohydrates. Figures 4, 5 and 6 highlight some easily digestible carbohydrate sources to use during and around training.Figure 5.: Pre-exercise: 30 to 60 minutes before nutritional goals and guidelines.Figure 6.: During exercise nutritional goals and guidelines.PROTEIN Protein intake is usually easily met by a “typical” mixed diet. Vegetarian, vegan, or energy-restricted athletes should be assessed to make sure protein needs are being met. Although there is a misconception that meat is the only source of protein, legumes, nuts, seeds, milk, yogurt, soy, and eggs are examples of nonmeat protein foods. Usually a protein supplement is not necessary. More protein is often thought of as better, especially for athletes trying to gain muscle or “bulk up.” To gain muscle, or weight, in general, an individual must be taking in more calories than expending. If an athlete is eating more protein than recommended, but still taking in less total calories than expending, weight or muscle gain will not occur. With protein, try to stress a “food first” approach as well as spreading protein “feedings” throughout the day. Food is the superior source of dietary protein compared with supplements. Consuming protein 3 to 5 times per day in about 20 to 30 g doses provides multiple stimuli to maintain and build lean muscle mass.7 One of these doses should be postworkout when nutrients are delivered to muscles and cells quicker. Protein, along with carbohydrate, post-exercise will help prevent further muscle breakdown and activate muscle repair.3Table 2 provides examples of 20-g protein servings, while Figure 7 gives examples of postworkout snacks and meals.TABLE 2.: Example Foods Providing ∼20 g of ProteinFigure 7.: Post-exercise nutritional goals and guidelines.FAT Fat in the diet is essential for absorption of fat-soluble vitamins and production of cholesterol and sex hormones. Although adolescents use fat more readily as a fuel source during exercise compared with adults, adult recommendations are still used.1 Around 25% to 30% of total daily energy intake should come from fats with less than 10% to 15% from saturated fat sources.7 This is where snack and convenience foods come into play. For many adolescents, snack and convenience foods contribute a bulk of total calorie intake—most of which are higher in fats and saturated fats (along with simple sugars). Finding healthier substitutions for “junk food” or decreasing the occurrence of snack/convenience foods in the diet is the best place to start making changes for this macronutrient. Refer to Figure 8 for examples of healthy snack foods.Figure 8.: Healthy snacking list.VITAMINS AND MINERALS Multivitamins If an athlete is consuming a well-balanced diet that provides enough calories to meet standards of growth and activity levels, a multivitamin supplement is, most likely, not required. Consider a multivitamin for those who are amenorrheic, iron-deficient, experience food insecurity, restricted food groups such as vegetarians and vegans, or have restrictions due to multiple food allergies.1 Multivitamins have not been shown to enhance athletic performance, and mega supplements or ultrasupplements are not recommended. Calcium and Vitamin D Calcium is essential for bone growth, bone mass, nerve impulses, and muscle contraction. Bone development and bone accrual is at its highest rate during adolescence and calcium is a mineral that should be assessed individually.6 The recommended dietary allowance (RDA) of calcium for adolescents is 1300 mg/d6. Milk, cheese, yogurt, calcium fortified foods/juices, soy products, and cereals are good sources of calcium in the diet. Dairy products and nondairy milks are the main source of calcium in a “typical” diet. However, many times if energy is restricted, dairy products are also restricted. Less than 15% of female atheletes 9 to 18 years old meet the recommended calcium intake.8 Calcium supplements are not good substitutes for dietary calcium in regards to impacting bone health but should be considered if dietary needs are unable to be met with food.8 Vitamin D also plays a role in bone health and the absorption of calcium. The RDA is 600 IU/d for 4 to 18 year olds.8 Supplementation should be considered and serum levels checked for those living in the northern hemisphere and/or who play and train indoors. Iron Iron is another mineral that may need to be evaluated individually. Iron is essential for energy metabolism and oxygen transportation through the body. Iron deficiency and/or iron depletion is a common problem in adolescent athletes due to increased requirements and turnover, but particularly female athletes.1 Iron levels are more of a concern among female athletes, with need increasing after menarche. Low iron can cause decreases in performance such as excessive fatigue, impaired muscle function, weakened immunity, and decreased ability to make decisions.1,3 The RDA for boys aged 9 to 13 years is 8 mg/d and 11 mg/d for 12 to 18 year olds.7 Girls aged 9 to 13 years also have an RDA of 8 mg/d but this increases to 15 mg/d at the 14- to 18-year age range. Food sources of iron are red meat, pork, chicken, eggs, fish, dried fruit, leafy greens, peanuts, beans, and some fortified beverages and cereals. Pairing sources of iron with food high in vitamin C (citrus fruits, orange juice, etc.) helps absorption of iron in the body. Anemia blood tests and iron screenings should be considered for male and female athletes experiencing any of the symptoms listed above, following a vegetarian diet, or have been consuming a low-energy diet for an extended period of time.1 Iron supplementation is not advised without a diagnosis of anemia or deficiency because iron toxicity is a risk especially in the younger population. HYDRATION There has been a long-held belief that adolescent athletes are at greater risk for dehydration due to greater heat stress and heat accumulation; however, current research indicates children are not uniquely vulnerable to heat illness.9 That being said, attention should be paid to adequate fluid consumption and prevention of heat illness for any athlete. Fluids should be consumed throughout the day, not just around practice. If an athlete tries to hydrate right before practice, he/she will still be dehydrated. Physicians can help encourage consumption of water or low-calorie flavored drinks throughout the day, as well as with meals (low-fat milk is also a good option at meals). Limited access to fluids during the school day, the inability to leave class to use a drinking fountain or not being allowed to carry a water bottle can be barriers to appropriate hydration. Along with hydrating during the day, athletes should also consume fluids during activity. Table 3 displays suggested amounts of fluids before, during, and after exercise, although tolerance to amount and needs vary.10 Using preworkout and postworkout weights and adjusting fluid recommendations to fit sweat rate are the best ways to account for individual need and tolerance. See Table 4 for an example using preworkout and postworkout weights for fluid recommendations.3 Generally, for activity lasting less than 60 minutes, water is adequate. For exercise lasting longer than 60 minutes, carbohydrate ingestion during exercise may be beneficial, especially in very hot and humid environments.3Figure 6 presents methods to achieve carbohydrate consumption during exercise.TABLE 3.: Hydration Guidelines Before, During, and After Training10TABLE 4.: Example Hydration Calculations Using Preworkout and Postworkout Weights3Consuming a sports drink is a convenient way to add carbohydrates, fluids, and electrolytes, when deemed appropriate, during exercise. Use of sports drinks outside of physical activity can lead to excessive sugar and calorie intake, which may lead to dental caries, being overweight, and obesity.11 Use of a sports drink during activity should be suggested on an individual basis based on training environment, duration, intensity, and the teen's overall health. It is important to note sports drinks and caffeinated energy drinks are not one-and-the-same. A sports drink is a “flavored beverage containing carbohydrate, minerals, electrolytes (eg, sodium, potassium, calcium, and magnesium), and sometimes vitamins or other nutrients.”11 An energy drink is usually characterized by containing stimulants (caffeine, green tea extract, and guarana), along with carbohydrates, amino acids, vitamins, and minerals.11 Making sure adolescents know the difference and risks associated with energy drinks is crucial. Some athletes may be considered “salty” sweaters and require extra sodium in their diet. Signs of excess salt loss include sweat that burns/stings the eyes, caked salt (salt on skin, clothes, and hats), and sweat that tastes salty.10 In this case, using a sports drink or adding a small amount of extra salt (1/4 teaspoon of table salt per 1 L of water) to fluids might be necessary. Encouraging the athlete to eat salty snacks such as pickles, crackers, pretzels, and/or adding salt to foods can also help. PERFORMANCE-“ENHANCING” SUPPLEMENTS Adolescent athletes will gain more performance improvement through healthy growth, maturation, regular training, and adequate nutrition than any supplement may provide. There is limited research on the short- and long-term risks of supplement use in athletes younger than 18 years. Education needs to start earlier within sports teams and schools about the efficacy and safety, or lack thereof, for performance-enhancing substances/supplements. As stated previously, making sure adolescents know the difference and risks between energy (caffeine-containing drinks) and sports drinks is needed. FAD DIETS There are a lot of fad diets touting the benefit of improved performance to the athletic population. Some of these trending diets do have merit for health, such as a gluten-free diet, when medically appropriate, but do not enhance athletic performance. Athletes who exclude certain foods or food groups are at risk of not meeting nutrition guidelines for general health and sport. There are pros and cons to any diet, as well as potential benefits and consequences for the athletic population. Low-Carbohydrate High-Fat or Ketogenic Diet The premise behind the ketogenic diet is to limit the amount of carbohydrate available for the body to use as fuel, thus increasing the ability of the body to use fat for energy during exercise.12–14 In most research, a high-fat, low-carbohydrate diet presents as less than 60% to 65% of total energy intake from fat and carbohydrate below 20 g per day or less than 20% of total energy intake. Although the use of a high-fat, ketogenic diet revealed higher rates of fat oxidation, no performance benefits have been shown in endurance or high-intensity exercise thus far.12–14 The capacity for high-intensity exercise is actually at risk of being compromised while following a ketogenic is still the of ketogenic diets in particularly with To a high-fat, low-carbohydrate diet, as above, be for the adolescent population. do not foods or food groups if it is not medically necessary. Consuming less than 20 g of carbohydrates a day foods such as milk, yogurt, fruit, and starchy Carbohydrate foods provide not only the energy but also vitamins, minerals, and during the growth and development of a diet may also lead to a greater intake of saturated a factor in increasing the risk of in Diet The diet is around the approach of eating in the Foods considered are fruits, lean eggs, fish, nuts, and legumes, and dairy are from the diet. In the behind the diet lead to low carbohydrate vegetables and higher protein, and to higher fat intake. dairy is calcium intake usually is A by revealed that calcium intake on the diet at of the recommended dietary this intake of fruits, lean and healthy it is very The amount of in a day is restricted, and as stated before, starchy and are restrictions low carbohydrate intake, which can energy levels, and total calorie intake for foods may also be for an adolescent athlete to and keep for a The of the diet is to be 10% more than a diet of nutritional to a diet may body weight and/or body fat there are less ways to get the of is more used as a weight loss than for increased performance. However, many athletes the they the they will for a period with to no eating then after The is that and eating opportunities to a of time and decreases overall calories Although may body weight and/or body fat it risks and for A common in is to the from then only a to for eating at the of the day. Consuming enough calories during this time can be a and of for during, and post-exercise cause performance and For from exercise, athletes should consume carbohydrate and protein within 60 minutes after exercise. In the first 2 to 4 hours after muscles are to store glycogen more while the of protein the body from muscle breakdown to from exercise may also be impaired during As with calorie the limited time for consuming foods and fluids will make it to drink enough to Diet A gluten-free diet the protein in and diets are medically for those with or a athletes that There is no evidence-based research that a gluten-free diet is or increases or decreases in diets may be in protein, and vitamins while being higher in sugar and can lead to an on consuming fruit, and gluten-free grains. As diagnosis of and has there has been growth in the of healthy and gluten-free foods. However, athletes for competition may still have with of gluten-free foods. foods also tend to be more than It may be for athletes to carbohydrate needs with the of carbohydrate foods recommended to athletes, such as See the just the athlete. Healthy growth, maturation, and development should be the first but this may not be the teen's first should be made to how these physical changes are and of who the and of meals and include on any nutrition not nutrition is at any certain and are often the main sources of nutrition for this and this may not be teens to eat 3 meals 2 to 4 snacks foods should be but not restricted Hydration should be an not only during If weight loss is weight loss or weight is the goal as they are still and can into their A referral to a registered dietitian should be made to achieve this If an athlete is following a diet, for and should be changes simple and any nutritional to performance as a For how can food choices and food performance. when more the changes seem more For low-calorie flavored water water or food 4 times per 2 times per with daily 3 times per with 2 a approach with and diet still may not be where to but if he/she is making changes in the right that should be