Читать книгу Eating for Sport - Shelly Meltzer - Страница 31

1. My 12-year-old daughter needs to lose weight for gymnastics. Can I cut her energy intake to 5000kJ (1200kcal) per day?

Severe and prolonged low-calorie diets are not recommended for young athletes since this may compromise the energy required for training, results in short stature and delays puberty, causes menstrual irregularities, increases the incidence of injuries and the risk of developing eating disorders. Therefore a diet of 5000kJ (1200kcal) may be too low, but an adequate calorie deficit can be achieved by simple lifestyle changes, such as better snack choices and less time spent watching TV. There is a very close correlation between the time spent watching TV and weight gain. Not only is this inactive time, but the advertising of fast foods and inappropriate snacks encourages poor food choices.

2. How much protein should young rugby players eat to build muscle?

Children and adolescents do require more protein than adults because of the extra protein required for growth. Protein is also required for gains in lean body mass and to compensate for protein used as a source of fuel in exercise and for muscle regeneration. However, there is a limit to the amount of protein that the muscle can use. It is also important to have sufficient carbohydrate together with the protein, because carbohydrate provides the necessary energy to fuel the work that the muscle must do to stimulate it to grow. It is therefore generally recommended that young rugby players consume 2g protein/kg body weight (for instance, a 60kg/132 lb player would need 120g protein per day).

Examples of low-fat foods that provide 10g protein per portion are listed on p22. See also p23 for practical tips.

3. Will creatine help my son’s soccer performance?

Creatine, an amino acid compound popularly taken as a supplement (see p97) is not recommended for children under the age of 18. In some situations and only in some individuals, creatine may enhance performance. However, it may have side effects and although a lot of these are anecdotal, no long-term studies have been done on adolescents. A concern with children taking creatine is that in a developing skeletal system, the increased force of the muscle (as a result of creatine supplementation) may lead to injury. Also, because water is transported into the muscle cells with creatine, large doses may be disadvantageous in the heat, especially in children who already are at risk for dehydration. Rather, they should stick to natural food sources of creatine – meat/fish/chicken/lean dried meat such as beef jerky. Some of these costly products may also contain ingredients that could be banned and at the end of the day the onus is on your son.

4. Should my talented child take a multivitamin or mineral supplement?

A daily vitamin and mineral supplement for well-fed, healthy, growing children is unnecessary, since their diets generally supply sufficient vitamins and minerals to meet their requirements. If parents wish to supplement their child or adolescent’s diet with a multivitamin and mineral supplement, it is important to make sure that the supplement contains all or most of the vitamins and minerals according to the DRIs, or at least 50–150% of the DRIs. Some supplements do not contain enough iron, calcium and zinc or other minerals and therefore emphasis should be on achieving an adequate diet first. Megadoses of vitamins and minerals (doses greater than 10 x RDA) should be avoided as they may be toxic. The need for supplementation is, therefore, best addressed on an individual basis by a registered sports dietitian or medical doctor (see p96).

5. Are sports drinks necessary for young soccer players and how much should they drink?

Sports scientist Oded Bar-Or recommends the following broad guideline for children (1995): ‘Drink periodically until not thirsty anymore, and then another few gulps.’ Another few gulps would mean about 100–125ml (about½cup) beyond thirst for a child younger than 10 years and 200–250ml (¾–1 cup) beyond thirst for a child older than 10 years.

After training your child will still continue to lose fluid and so should continue drinking until he is urinating frequently.

Drinking is important to replace fluid losses and young athletes often begin training after school when they are already dehydrated. Fluids can also provide energy in the form of carbohydrate. Sports drinks provide both carbohydrate and fluid, but so does fruit juice (preferably diluted by 50%), diluted cordial, or even a carbohydrate powder when added to water. Although sports drinks may contain some other nutrients (for example, some electrolytes like sodium and potassium), snacks and food generally provide a more significant amount of these electrolytes. Some sports drinks may have added vitamin C, which is of course present in most fruit juices. So when it comes to choosing between any of the above drinks, choose what suits your pocket and a flavour that your child enjoys, since if he likes the taste he is likely to drink more.

6. Is all this carbohydrate detrimental in terms of dental health?

Dental caries, or tooth decay, is the result of repeated acid attacks by bacteria on dental plaque. Sugars provide the energy for bacterial growth and the acids formed by the bacteria from the sugar substrate gradually erode the tooth enamel, causing decay. Two conditions accelerate the process: sticky carbohydrates that stick to tooth surfaces for a long time; and frequent exposure of tooth surfaces to sugar. In other words, the total amount of sugar eaten is not as important in the formation of caries as the type of sugary food eaten, how often it is eaten and how long it sticks to the teeth. Sticky sweets are likely to be more harmful than a sports drink because, while providing the same amount of sugar, the drink is less likely to stick to the teeth for long. Eating five sticky sweets on five occasions during the day results in five exposures, while eating the five sweets at one time will reduce the total time of exposure. If eating or drinking sugary foods and beverages between meals, it is important to brush, floss and rinse the mouth afterwards.

Factors associated with dental caries:

▪ the physical form of the carbohydrate and the stickiness of the food

▪ the concentration of sugars in the foods consumed

▪ the length of time the teeth are exposed to acid

▪ the frequency of meals and snacks

▪ the proximity of eating to bedtime

▪ specific foods like citrus fruits and juices, carbonated and uncarbonated sugary drinks, acidic herbal teas, vinegar and vinegar products, sweets, acidic medications and supplements (for instance, vitamin C tablets and syrups).

To prevent dental caries, encourage your child to:

▪ brush and floss teeth regularly (this is very important if your child wears braces)

▪ rinse the mouth frequently with water

▪ consume casein-containing food like milk and cheese

▪ chew sugar-free gum

▪ drink through a straw or squeeze-bottle, since this minimizes contact time with teeth

▪ have drinks chilled to reduce the erosive effects of acidic drinks

▪ always be adequately hydrated as this will promote saliva, which is an important buffer that prevents erosion.

7. My son just refuses to eat fruit and vegetables. Can he simply replace this with a vitamin and mineral supplement?

The best strategy to obtain adequate nutrients in a form that is well absorbed by the body is to eat a variety of food. Of course, fruit and vegetables are especially rich in many vitamins, minerals and other phyto-nutrients. However, 91% of children aged 6–11 years do not consume the recommended minimum of five servings of fruit and vegetables per day. Most children average 2½servings a day, making it difficult to achieve adequate intakes of many vitamins. If your child has a particular aversion to fruit or vegetables, try some of the following tips before buying a supplement:

▪ Add vegetables to stews, soups (even puréed), casseroles, stir-fries, and to meat or chicken kebabs.

▪ Encourage fruit-based desserts (apple sauce, baked apple, fruit kebabs).

▪ Make fruit salad (often a child is too lazy to cut up the fruit).

▪ Dried fruit is a concentrated source of many nutrients.

▪ Fruit and vegetable juices or smoothies should take preference over colddrinks. 125ml (½ cup) fruit juice counts as a fruit serving.

8. Should my child only eat carbohydrate foods that are rich in fibre?

Children older than two years should aim for a daily fibre intake equal to their age plus 5g. Good sources of fibre include high-fibre cereals, wholegrain breads and crackers, oats porridge, legumes, fruit and vegetables. Avoid excessive fibre intake, which may reduce consumption of much-needed energy and nutrients, especially in active children. First ensure that your child achieves the basic fibre requirement beyond which you can be more flexible and include carbohydrate foods with less fibre.

9. My child is constantly tired. Can this be related to his diet?

Yes, although there are other factors, like overtraining and lack of adequate sleep. Check on your child’s overall energy, carbohydrate and protein intake, as well as certain vitamins (for instance, the B-vitamins) and minerals. Lack of dietary iron, for example, may cause fatigue. Rich sources of iron include meat, chicken, beef jerky, liver, spinach and some dried fruits. Post-training nutrition is also a factor. After exercise, there is a window period of 1–2 hours when the muscles have an accelerated ability to replace carbohydrate stores. Ensure that your child has something to eat after training, particularly if he spends time travelling home from training: a sandwich with a filling of cheese, fruit-flavoured yoghurt, a carbohydrate drink, fruit juice, a few crackers, a raisin bun, or a cereal/sports bar. Provided the snack supplies sufficient carbohydrate (about 50g – see p17) you can include some protein. Protein is especially important if there has been any muscle damage.

10. When my son goes away on cricket tour, how can I ensure that he eats properly?

If your child does not enjoy trying new foods or you are concerned about the food on tour, it is always a good idea to pack a supply of familiar foods to take with. Fresh and dried fruit, crackers, pretzels, muesli and breakfast bars, dry cereal (in serve-size packets), skim-milk powder, a tin of low-fat liquid meal replacement powder, fruit juices, instant oats or quick-cooking noodles (if a kettle is available), and carbohydrate powders are suitable options.