PARIS — A child or adolescent athlete generally engages in school and extracurricular sports practice for more than 10 hours per week. High-level child or adolescent athletes engage in more than 20 hours of practice, excluding competitions.
Nutrition affects these athletes' growth, risk for injury, and performance. At the congress of the French Society of Pediatrics, Dr Emmanuelle Ecochard-Dugelay, of the pediatric gastroenterology and nutrition department at Robert Debré Hospital in Paris, reviewed the key points in monitoring and advising these young athletes for the Medscape French edition.
Why is it important to be concerned about the nutrition of a child or adolescent athlete?
Adequate nutrition in the context of sports practice helps to avoid several problems, including energy deficit, which decreases performance; growth delay; and pubertal delay. In addition, a micronutrient deficiency can increase the risk for injuries and fatigue. Often, adolescent athletes tend to favor high-energy density foods that are low in nutrients, mainly starches, at the expense of fruits and vegetables. This leads to frequent deficiencies in micronutrients such as vitamins and trace elements.
Are eating disorders more common in weight category sports?
Indeed, in boxing, judo, and wrestling, young athletes may be required to maintain a specific weight for their category, which can compromise their optimal energy intake and growth. In boxing, for example, they aim for the upper limit of a weight category rather than the lower limit of a higher category. Other situations also pose nutritional risks, such as sports with low weight requirements (eg, gymnastics, dance, skating, jockeys) or those with high body representativeness (eg, rugby, weightlifting). Adolescents with exclusion diets (eg, vegans) or chronic illnesses must also adapt their diet and training.
In clinical practice, I often see young athletes for issues related to growth, nutrition, or weight. Some seek nutritional follow-up to optimize their sports performance, whereas others may require special attention owing to chronic illnesses or intensive sports practice. High-level athletes can get specialized consultations, such as those offered at France's National Institute of Sport, Expertise, and Performance or within federations.
What particularities should be considered in young athletes?
Differences in muscle fiber types between children, adolescents, and adults have implications for nutrition. Children have a higher proportion of type I muscle fibers (progressing gradually to a predominance of type II fibers in adults). This specific childhood muscle composition promotes the ability to sustain prolonged efforts. The fibers are more resistant to fatigue and are rich in mitochondria, with a strong capacity for aerobic oxidation and low anaerobic glycolysis. Hence, they have little lactic acid. Monitoring children and adolescents to prevent nutritional deficiencies or energy deficits is essential for optimal muscle development and growth.
Does their energy metabolism differ from that of adults?
In children, metabolic pathways are preferentially used during physical exercise, with aerobic glycolysis taking precedence over anaerobic glycolysis very quickly during exercise and in higher proportions. As a result, the energy needs of children per unit of weight far exceed those of adults owing to their ongoing growth and development. In other words, at an equivalent level of exercise, a child's energy consumption is higher than that of an adult per unit of weight owing to increased metabolism, in addition to growth-related needs.
Recommendations for energy intake include the following points:
Boys (15 years old): 3640 ± 830 kcal/d
Girls (15 years old): 3100 ± 720 kcal/d
Bosy (15-18 years old): 3000-6000 kcal/d
Girls (15-18 years old): 2200-4000 kcal/d
These recommended energy intakes vary according to the sports practiced.
Moreover, in children, and to a lesser extent in adolescents, thermoregulation is also more variable. Children have a larger ratio of body surface area to weight than adults do and possibly lower efficiency of sweat glands. Children also have increased sensitivity to hypoglycemia.
Regarding macronutrients in adolescent athletes, what should their protein intake be?
Several factors influence muscle mass gain in adolescents, and muscle recovery is essential. Consuming protein recovery products alone is not sufficient to build muscle. In fact, from the perspective of recovery, protein recovery products are not necessary for adolescents living in industrialized countries, unless they follow a specific diet (vegan, vegetarian, or celiac).
During the growth and tissue-building period, recommended intakes are higher than for the general population: between 1.2 and 1.4 g/kg/d, compared with 0.9 g/kg/d (representing 12%-15% of the daily intake). Sources of good-quality protein, preferably of animal origin, are recommended, because they provide essential amino acids needed for muscle synthesis and growth.
Consuming a carbohydrate-protein snack after exercise is advised to promote recovery and muscle growth.
What about carbohydrate and lipid intake in these young athletes?
Carbohydrate intake should generally represent between 45% and 60% of the total daily energy intake. The recommended quantity varies from 4 to 10 g/kg/d, depending on the intensity of physical activity. Adolescents have a low glycogen synthesis capacity. Their needs are usually met by a normal diet, focusing on low-glycemic index carbohydrates to optimize energy management and avoid gluconeogenesis from protein reserves.
On the other hand, lipid intake should represent approximately 35% of the total energy intake. Unsaturated fatty acids, which mainly are found in oily fish, dairy products, and vegetable oils (especially rapeseed), are recommended, as is maintaining a good omega-3/omega-6 balance. Avoiding fried foods is advised to limit saturated and trans fat consumption.
What are the potential micronutrient deficiencies?
Although micronutrients do not play a direct role in energy production, they are essential for metabolism and most biochemical processes. A deficiency in micronutrients can lead to poor recovery, increase the risk for injuries, and affect sports performance.
Among the most common micronutrient deficiencies in adolescents are deficiencies in vitamins D, C, and calcium. Vitamin D deficiency is often detected in people with insufficient sun exposure or limited dietary intake.
Calcium and vitamin D play a crucial role in calcium homeostasis, which is essential for muscle contraction and bone formation. Some populations are particularly at risk: girls, who do not benefit from testosterone protection and may be subject to dietary restrictions, as well as athletes who play indoor sports. Most adolescents receive their calcium intake through dairy products, but it is advisable to ensure that they consume at least four servings per day for adequate calcium intake.
Vitamin C is often deficient in people who consume a lot of starches while neglecting to eat fruits and vegetables, which are important sources of this vitamin. If in doubt or if the person's diet does not seem balanced, then these intakes should be checked through a detailed survey.
Generally, micronutrient supplementation is not recommended for children who have a balanced and varied diet, because their diet should suffice to meet their needs. However, if the diet is unbalanced, if the practice is intensive, or if symptoms of deficiency appear, supplements may be necessary, followed by supplementation to ensure adequate intake.
What about the use of dietary supplements?
From 20% to 80% of young athletes take dietary supplements. The most common include multivitamins, vitamin C, and caffeine. Often, their use is not medically justified, and there is little rigorous evaluation of the products available for sale. Furthermore, some supplements may contain doping agents.
What are your recommendations regarding hydration in young athletes?
Hydration should not be overlooked, because a 1% fluid loss can lead to a 10% decrease in performance. Here are the recommendations: During activity, it is recommended to drink 13 mL/kg/h (approximately 500 mL/h for a 40-kg child). After activity, it is recommended to drink around 4 mL/kg/h for each hour practice of practice.
Regarding flavored solutions containing carbohydrates and salt (NaCl), few specific studies have been done in children.
What are your messages to doctors following these children?
Briefly, identify risky situations and tailor advice to the type of sport and its intensity.
Many children, without being high-level athletes, practice at least 10 hours of training or competition per week in addition to school sports. It is therefore common for a doctor to encounter them among their patients. It is important to ask about their sports practice to understand their specific needs and to track their growth curve and observe their pubertal development. This is not only to minimize the risk for injuries but also to preserve their weight and height status into adulthood, as well as their bone health. I recommend referring them to dietitians or specialized nutritionists, especially those from sports federations, for optimal support in terms of their sports performance and overall health.
Ecochard-Dugelay reported having no relevant financial relationships.
Note: This article originally appeared on Medscape.
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