Karate Athlete - Youth in Sport: Nutritional Needs

Youth in Sport: Nutritional Needs
GSSI Roundtable Discussion

Oded Bar-Or, M.D. Children's Exercise & Nutrition Center McMaster University Hamilton, Ontario, Canada	Susan Barr, Ph.D. School of Family & Nutritional Sciences University of British Columbia Vancouver, BC, Canada
Michael Bergeron, Ph.D. Department of Exercise Science University of Massachusetts Amherst, MA	Ruth Carey, R.D. Chair Elect Sports, Cardiovascular, and Wellness Nutritionists Portland, OR
Priscilla Clarkson, Ph.D. Department of Exercise Science University of Massachusetts Amherst, MA	Linda Houtkooper, Ph.D., R.D. Department of Nutritional Sciences University of Arizona Tucson, AZ
Anita Rivera-Brown, M.S. Center for Sports Health and Exercise Sciences Albergue Olimpico and Dept. of Physical Medicine, Rehabilitation and Sports Medicine University of Puerto Rico School of Medicine Salinas, Puerto Rico	Tom Rowland, M.D. Pediatric Cardiology Baystate Medical Center Children's Hospital Springfield, MA
Suzanne Steen, D.Sc., R.D. Graduate Division Dept. of Nutrition Education Immaculata College Immaculata, PA

Courtesy of the Gatorade Sports Science Institute

KEY POINTS

1. Young athletes should eat a variety of foods that provide 12-15% of total calories from protein, at least 55% from carbohydrate, and up to 30% as fat. The Food Guide Pyramid provides a practical way of meeting these recommendations.

2. The key nutrients needed to assure adequate intake in physically active youths are carbohydrate (including fiber), B6, vitamin D, iron, calcium, magnesium, zinc, and chromium. A balanced meal plan that does not exclude any food groups will maximize the child's chances of obtaining all the nutrients in amounts needed for growth and training demands.

3. Fluid intake should be encouraged before, during and after activity and sports to prevent dehydration.

4. With a balanced diet, dietary supplements are unnecessary.

INTRODUCTION

A lifetime appreciation for physical activity and sports participation often starts during childhood. Proper nutrition is one factor that can contribute to making sports a positive experience for kids. If kids are well hydrated and adequately fueled, they will get more out of practice and the remainder of their daily physical activities than if they are not nutritionally prepared. To help with the nutritional preparedness of young athletes, the experts in this discussion address questions commonly raised by young athletes and their parents.

1. What foods or nutrient supplements should teens eat to help them grow larger, stronger, and faster?

Barr: "Growing larger" is mediated primarily by genetics, but young athletes may fail to reach their genetic potential if the energy demands of growth and training are not supported by adequate energy intakes. This concern may be particularly apparent in sports such as gymnastics, in which heavy training begins at a young age. This can result in an energy imbalance at a time when kids can least afford it. However, failing to meet energy needs can occur among athletes competing in other sports as well. In this situation, frequent meals and snacks are indicated.

Athletes often think of protein in association with "growing stronger." Recent evidence supports the concept that protein intakes above RDA levels are needed by adult strength athletes (to support gains in lean body mass) and endurance athletes (to compensate for use of protein as a fuel source). Intakes of 1.2-1.5 grams of protein per kilogram body weight per day may be appropriate for adult athletes, compared to the adult RDA of 0.8 g/kg/day. Unfortunately, data assessing teen athletes' protein needs are not available, but it is within reason that their needs might also be elevated above RDA, which ranges from 0.8-1.0 g/kg/day for teens. More importantly, recommending that growing athletes include high quality protein sources in their diets seems prudent. Protein supplements, however, are not warranted because the diet typically provides generous amounts of protein if energy needs are met.

Clarkson: The second highest peak growth velocity occurs during adolescence, and there are dramatic changes in body composition. Unless under the guidance of a physician, teenagers should not be restricting calories and they should not skip meals. A restriction of calories could limit linear growth. If an objective assessment, i.e., body fat test shows that a teenager can lose weight, the first "line of defense" should be to adjust food choices so that less high-fat snack foods are eaten and more fruits, vegetables, and whole grains are consumed.

Surveys of adolescents, both athletes and the general population, show that sufficient amounts of protein are consumed but carbohydrate intake may be somewhat low and fat intake somewhat high. The proportion of protein, carbohydrate, and fat in the diet should be about 12-15%, 55-60%, and 25-30% of total calories, respectively.

A neglected component of the diet of many adolescents is fiber. The recommendation for children older than 2 years of age is equivalent to age-plus-5g fiber/day, with a safety range of age-plus-5 g/day to age-plus-10 g/day. More than half of all children and adolescents are not meeting minimum fiber intake recommendations. Foods high in fiber include fruits, vegetables, cereals, and other whole grain products. Because dietary fiber increases water retention in the colon, intake of water and other fluids should be increased when switching to a higher fiber diet.

Steen: Well-meaning, but misinformed parents and coaches may advise children to take supplements in an effort to promote early athletic development, improve performance, and as "health insurance." However, physical maturity and athletic prowess do not necessarily depend upon how early a child reaches adolescence, and in any event, the process will not be facilitated by dietary supplements.

Supplements can give kids a false sense of security and may encourage faulty eating habits. Kids and teens may assume that their morning dose of supplements provides them with all of the nutrients that they need, so that they end up eating foods with low nutritional value. With supplement use the child athlete may erroneously associate improvements in performance with whatever supplements they may happen to be taking. They may be less likely to attribute progress to training, hard work and a balanced diet - the factors that really make the difference. Megadoses of supplements do not make up for a lack of training or talent, and in certain cases may be dangerous.

To move away from this reliance on "supplement insurance," young athletes need to feel confident about eating "ordinary foods" to promote muscle growth and optimal performance. Young athletes should concentrate on eating a variety of foods to meet vitamin and mineral needs. This is an important reason to encourage young athletes to keep records of what they eat, when and how hard they train, and how their performance improves.

2. Can teenagers in scholastic or club sports benefit from eating a high-carbohydrate diet to prepare for competition?

Bar-Or: Data are not available regarding the practice, benefits, or detrimental effects of carbohydrate loading in children or adolescents. Nor is there data available on the optimal pre-competition meal in these age groups. Likewise, there is no information regarding gastric emptying rate, intestinal absorption rate and utilization of ingested carbohydrates in exercising children and adolescents. Some data, however, suggest that, compared with adults, pre-teens utilize more fats and less carbohydrates during prolonged exercise.

Because of the lack of scientific data, the implications of carbohydrate loading or the addition of carbohydrates to the pre-competition meal, are not clear in children. A practical approach for the parent would be to try the addition of a modest level of carbohydrate to the regular diet of child athlete during the pre-competition period and see how the well-being and performance are affected. If no detrimental effects are observed, one may gradually increase the carbohydrate content in the food.

Rivera-Brown: Although the effect of a high-carbohydrate diet in the child athlete has not been researched, adolescent athletes may benefit because of being more similar to the adult athlete in whom the benefits of high-carbohydrate diets are well founded. The composition, and the timing of the meals of teenage athletes should be carefully supervised. During the entire week preceding a competitive event adolescents should eat a diet that provides adequate carbohydrate. Adolescent athletes who train or compete in the morning, especially those involved in endurance sports, should be encouraged to eat, not skip breakfast. A meal high in carbohydrate could help prevent a premature lowering of blood glucose that occurs if glycogen stores are low after an overnight fast. For those who train or compete during the afternoon or evening, it is recommended that two-to-three hours before the exercise session or competitive event, they drink fluids and consume foods that are high in complex carbohydrates (e.g., fruits, breads, cereals, pasta, or rice). For athletes who feel nervous and prefer not to eat much before competition, carbohydrate energy bars or fruits are a good alternative. Snacks such as bagels, crackers, fig bars, bananas, juice, and granola, and carbohydrate drinks should also be offered during the day. After an exercise session, adolescents are usually thirsty and hungry and will eat whatever is quickly available. This is a good time for consumption of complex carbohydrates to replenish carbohydrate stores. Sports drinks are also recommended and will aid in rehydration and carbohydrate replenishment.

Houtkooper: Regardless of age, carbohydrate and fat are the main fuels the body uses for energy. As Dr. Clarkson recommends, carbohydrate should be at least 55% of calories, and possibly as high as 70% for older adolescents who undergo heavy training for endurance sports. Carbohydrate is undoubtedly the limiting form of energy stored in the body, and only by consuming adequate amounts of carbohydrate can athletes effectively replace glycogen stores.

Foods providing carbohydrates as simple sugars and complex carbohydrates can be used to replenish body carbohydrate reserves. Complex carbohydrates such as starch, can be found in the grains food group, which includes breads, cereals, rice, pasta, crackers, and in vegetables. Simple carbohydrates can be obtained from fruits, milk, soft drinks, table sugar, fruit juice, honey, and candy. Grains, vegetables, fruits, and milk also provide lots of vitamins and minerals. Eating a variety of foods that are rich in complex carbohydrates and that also provide some simple carbohydrate will give teens the foundation for a nutritious diet. Eating foods such as low-fat milk and milk products, and lean meat, poultry, and fish will provide the protein needed by active kids. If energy intake is adequate to meet the needs for growth and activity, protein requirements will be met.

The general guidelines for encouraging carbohydrate intake should be relevant to teenage athletes. This certainly applies for the health benefits if not for optimizing athletic performance.

3. Are there any specific minerals or vitamins that are deficient in the diet of active children or teens?

Rowland: Studies surveying dietary intake of active children and adolescents commonly identify deficiencies of two important micronutrients - iron and calcium. This observation is particularly disturbing considering these micronutrients are critical not only to good health but also in optimizing athletic performance. Calcium is necessary for the development of bone mass, a process that may protect against osteoporosis in adulthood. Iron deficiency causes anemia, which limits oxygen transport in the blood and impairs exercise performance. It is possible, too, that low iron stores - even without overt anemia - may interfere with normal muscle oxidative metabolism and depress cognitive function and motivation. These effects of low body iron clearly signal the need for athletes to assure adequate iron stores through proper diet.

A major reason that dietary calcium and iron are low among adolescents is their tendency to shun dairy foods and red meat, either from concern over fat intake or desire for a vegetarian diet. Kids need to be convinced that regular consumption of dairy products is important in assuring adequate calcium in the diet. They should also be encouraged to eat lean red meat at least three times a week. Other sources of iron can be consumed as alternatives, including iron-fortified cereals.

Barr: Most young athletes expend more energy and have correspondingly greater food intakes than normally active children or teens; accordingly, their vitamin and mineral intakes also tend to be higher. However, as Dr. Rowland points out, calcium and iron are the two minerals that are worth watching in the young athlete's diet.

Generous intakes of calcium along with physical activity during growth are thought to contribute to maximizing peak bone mass. Achieving optimal bone mineralization may reduce young athletes' risk of stress fractures during their athletic careers and help minimize the adverse consequences of bone loss later in life. Poor iron status among female athletes is a consequence of menstrual losses in girls and inadequate dietary intake. Young females who exclude red meat should pay particular attention to the iron content of their diets, and in some cases, may need to use an iron supplement. However, therapeutic doses of iron shouldn't be used unless iron deficiency has been diagnosed, as higher-than-normal doses of iron may interfere with absorption of other trace minerals.

Bergeron: Like adults, children and teenagers lose electrolytes in their sweat; although, the concentration tends to vary with maturational-related changes in sweating rate. Therefore, young athletes can potentially face similar sweat-induced mineral imbalances, as a result of excessive and repeated sweat losses, as some adults do. I have particularly observed this to be the case with sodium. However, I personally have not come across a case of heat-related muscle cramps (related to chronic and progressive sodium and fluid deficits) in a boy or girl below the age of 15. This may be related to the lower sweat rate and sodium concentration generally observed with the younger age group.

Houtkooper: To meet their growth needs, adolescents require higher intakes of some vitamins than those for adults. The need for riboflavin is higher because of increased energy intake, but intake is frequently low in teens, especially in girls. Folate and vitamin B12 needs are increased because of the high rates of growth. Vitamin B6 is essential for the protein synthesis that occurs during rapid growth. The intake of this vitamin is often low in girls. The needs for calcium, iron, and zinc increase substantially during the adolescent growth spurt. All three of these minerals are frequently deficient in the adolescent diet.

Though the need for calcium and iron can't be emphasized enough, other microminerals should not be ignored. In physically active children, the recommended dietary allowances (RDA) for zinc and the safe intake levels for chromium are not increased, but the intakes of these two minerals tend to be low. The current RDA for zinc is 10 milligrams for children and 15 milligrams for adolescents; the estimated safe and adequate daily dietary intake for chromium is 50-200 micrograms. Young athletes are encouraged to increase their energy intake by consuming foods rich in zinc (e.g., shellfish, especially oysters; meat, eggs, wheat germ) and chromium (e.g., meats, unrefined food, whole grains, cheese). This will help ensure that they meet their needs. In theory, the losses of any mineral in the sweat or urine might increase with exercise, and thereby confound the problem of maintaining adequate balance.

Clarkson: Adolescents need to recognize the value of eating a variety of foods that includes protein and milk. For example, to ensure getting enough iron, they should consume meat, fish, and poultry that provides heme iron, which is more absorbable than non-heme iron found in vegetables and grains. Teenagers sold on vegetarianism will need to maximize their absorption of non-heme iron. Vitamin C will enhance absorption of iron in the diet. Tea, coffee, and foods with the preservative EDTA (e.g., fats and soft drinks), will inhibit absorption. Therefore, rather than drinking coffee with cereal, teenagers should drink orange juice. Milk should be consumed to provide not only calcium but also vitamin D. Milk is fortified with vitamin D, which plays a major role in calcium metabolism. Even when cheese and yogurt are eaten, less milk will mean less vitamin D.

A recent dietary survey of the general population found that in adolescents the intakes of magnesium and zinc were marginal. Following diets rich in a variety of fruits, vegetables, and whole grains, along with milk and a good source of iron, should be sufficient to provide the micronutrient needs of all teenagers. Whereas supplements of one micronutrient (e.g., just calcium, or just iron) can provide too much of the nutrient, which negatively affects the absorption of another, a balanced multivitamin/mineral supplement (containing 100% or less of the RDA) is not considered harmful and could be taken when young athletes are concerned that their diets may not be sufficient. All in all, though, the best source of micronutrients is food.

4. How concerned should parents be about the dietary fat intake of their children?

Carey: Typically what I find is that the fat content of a child's diet reflects that of the family. If parents are severely limiting the fat in the family diet, the kids will not get enough fat for normal growth and development. Disordered eating patterns may develop in young female athletes who have mothers and/or fathers who are very strict about dietary fat restriction. As a population, though, most kids and families in the United States are eating more fat than is healthful. Many families today have such busy schedules that they eat out more often and rely on fast foods and convenience snack items that are usually high in fat.

Of the 25-30% of the daily calories from fat (about 65 grams of fat per day), unsaturated fats should make up the majority. The more healthful unsaturated fats are found in vegetable oil-based products and fish. Saturated fats and animal fats should comprise only 10% or less of calories in the diet. The sooner parents and kids start a healthy lifestyle of moderation and balance in the diet, the better. Most habits, including our dietary practices, are formed early on in life.

Rowland: An overabundance of fat in the diet predisposes a child to obesity. There is no question that excessive body fat is a serious health concern because it significantly increases the risk of cardiovascular, orthopedic, and metabolic disease in the adult years. Furthermore, obesity during childhood increases the chances of becoming an obese adult. Parents should act to limit dietary fat in their children if it exceeds 30% of the daily energy intake.

At the same time it is important to avoid an obsession regarding fat intake. Lipids are important in the diet, serving as substrates for many critical biochemical and physiological functions. Moreover, fat adds flavor and enjoyment to eating. Over-concern regarding fat intake may lead to excessive weight reduction and eating disorders, particularly among teenage girls. "Fear" of eating fat may also cause adolescents to avoid consuming foods such as red meat and dairy products, important sources of iron, calcium, and vitamins.

Steen: The typical American diet supplies between 34-37% of the total calories as fat. This is too high. The young athlete may not be concerned with the adulthood diseases mentioned by Dr. Rowland, but the young athlete should know that consuming too much fat may displace other essential nutrients, such as carbohydrate that can affect performance and training. Kids eating too much fat should be encouraged to reduce consumption of high-fat food items such as chips, fries, and some desserts. Instead, they should substitute more healthful carbohydrate foods such as breads, pasta, fruits, vegetables, and low-fat dairy products. Within the recommended ceiling for total fat intake (30% of calories), cholesterol intake should be less than 300 mg per day. However, parents should be aware that these guidelines do not apply to infants and children less than 2 years.

A recurring theme here is that one should not be too strict or too liberal with fat. Taking too much fat out of the diet can take the fun out of eating! Severely restricting the amount of fat in a child's diet in an attempt to improve fitness can be detrimental - the child loses an important source of calories and an important source of fat-soluble vitamins. Certainly, prolonged restriction of fat and calories can have a negative impact on the child's growth and development.

5. How important is proper hydration and fluid intake in active kids?

Bergeron: In general, the importance of hydration for active children is similar to that for active adults. Even with the lower maximal sweating rates that are usually observed in children, kids can still experience dehydration, which will result in increased cardiovascular and thermoregulatory strain. Inadequate fluid intake could easily exacerbate the characteristic higher intolerance of exercise in the heat seen in children. This would place the active child at further risk for developing heat exhaustion or worse, heat stroke.

Bar-Or: Just like adults, children undergo progressive voluntary dehydration during exercise in a hot and/or humid climate. The extent of the dehydration is similar to that found in adults. However, the increase in core temperature at any given level of dehydration is quite a bit greater in children than in adults. For ethical reasons, no studies have examined the responses of children's core temperature, other physiological responses or perceptual functions to hypohydration of more than 3% initial body weight. Nevertheless, for safety considerations, one should assume that progressively dehydrating children would induce heat exhaustion and heat stroke earlier than adults.

The exact mechanisms for the poorer thermoregulation in the dehydrating child are not clear. It is known that children have a large surface area-to-mass ratio, their metabolic heat production during walking and running is greater than in adults, their cardiac output at any level of oxygen uptake is lower, and their ability to perspire is lower than in adults. All these factors may impede their ability to maintain thermal homeostasis during climatic extremes, particularly if they are dehydrated.

From a practical point of view, one should use any available means to prevent voluntary dehydration in active kids. Recent studies suggest that the presence of flavoring, sodium, and carbohydrate in a beverage enhances thirst and is effective in reducing/preventing voluntary dehydration in boys. Girls, possibly because of their lower sweating rates than in boys, may be less prone to voluntary dehydration. Nevertheless, in our observations, the carbohydrate-electrolyte beverage still elicited a greater fluid intake in the girls than did the choice of water alone.

Rivera-Brown: Heat acclimatized children, although better prepared to cope with a hot environment, are not exempt from the effects of dehydration. These children, especially if trained for sports competition, can exhibit very high rates of sweating during exercise. A high sweat rate improves heat dissipation but may also cause great fluid losses. Heat acclimatized children who participate in sports programs in tropical regions or during warm seasons may be in a state of chronic hypohydration if they train and compete frequently without replenishing their fluid losses completely. For these children, proper hydration before, during, and after training and competition is of utmost importance. Beverages that stimulate thirst, encourage drinking, and promote water absorption will help prevent dehydration. Studies in Puerto Rico with trained, heat-acclimatized children exercising outdoors have also shown that drinking a flavored, carbohydrate-electrolyte solution helps prevent voluntary dehydration during prolonged intermittent exercise in a hot and humid environment.

Dehydration that is used by child athletes to "make weight" in sports such as wrestling, judo, tae kwon do and boxing should be eliminated. These athletes purposefully become dehydrated by sweating during exercise in a hot environment and by restricting fluids during the days prior to competition. The benefits of keeping kids well hydrated prior to training and competition should be stressed. Rule changes may be necessary in sports such as soccer and field hockey to allow for an official "time out" for players to rehydrate.

Carey: Proper hydration is essential for the safety of active children. Kids' bodies do not regulate body temperature as efficiently as do adults' bodies and, therefore, active children are more susceptible to heat injury. Heat injury, usually complicated by dehydration, is the number two most common sports injury among kids, but is the most preventable.

Children should be encouraged to drink fluids frequently during activity. A general guideline is that kids should drink 4-8 ounces of fluids prior to activity and at least 4 ounces of fluids every 15 minutes during activity. After activity, children should consume at least 16 ounces for every pound of body weight that is lost.