Nutrition... One for the Parents and Pros

November 23, 2017

Basic Nutrition & Hydration Primer for Developing Youth Athletes

 

Energy Requirements

 

Everything has an energy requirement if it is required to react or move, regardless of whether you are sedentary or highly active. The only difference is that highly active people will require a greater energy input in order to balance out the great output, and vice versa.

 

Inadequate energy intakes can be detrimental to health and performance and has been reported to delay pubertal development. Therefore, ensuring energy needs are met during a growth phase is paramount for youth athletes.  It is important to note that high-intensity training under conditions of energy balance does not affect growth potential.

 

Inadequate intake is also usually accompanied with deficiency in several minerals including calcium, iron, and B-complex vitamins. In aesthetic athletes, such as dance, this may even extend to protein deficiency.

 

 

 

Macronutrients

 

Carbohydrates

 

Carbohydrates (CHO) are the main source of fuel for exercise and should aim to have at least 50% of your total energy intake from CHO. They can be categorised into starch and sugars, which can further be branched into intrinsic and extrinsic sugars. The difference between these two compounds is often misconstrued, and thus why I frequently get asked “is fruit bad for you?”.

 

Intrinsic sugars are ones that are not detrimental to health i.e. they are in their natural state. They are consumed as part of whole plants e.g. fruit and veg. Extrinsic sugars are not found within plant cells and so are rapidly absorbed and metabolised. They are found in syrups, juice, manufactured cakes etc. Extrinsic sugars (or now essentially termed ‘free sugars’) should make up no more the 5% of the total dietary energy.

 

CHO in the diet should be mainly whole grain and starchy; for example, pasta, brown rice, potatoes, couscous. These will fill you up and provide long lasting energy as it takes a while to absorb and metabolise.

 

 

 

Table 1 – Training intensity and the corresponding recommended CHO intake in grams per kilogram of body weight a day. For example, a 48.4kg ballet dancer (average weight) with moderate training hours, daily intake should be 290-339g CHO and 1102-1288 kcals/day of total energy intake. This would look like 1 large bowl of porridge, 1 peanut butter and jam sandwich, 1large jacket potato with 1 tin of baked beans and cheese, and 1 large banana.

 

Fats

 

Fats are a secondary fuel source, but are also vital for vitamin uptake and bone density. They are split into several groups as saturated and unsaturated, as well as omega essential fatty acids, and trans.

 

Around 40g/day of fat for female athletes is sufficient. <20% of energy from fat in the diet will have negative effects on performance. <6% energy from fat is dangerous. A healthy body fat percentage for female dancers is 8% and should not fall below this. Fat intake should range from 20%-35% of total energy intake.

 

Useful sources are oily fish such as salmon, mackerel, and sardines. Others include nuts, pulses, avocado, whole eggs, olive oil, and full fat yogurts.

 

Protein

 

Protein is required for growth and repair for muscle synthesis. It is recommended that intake is between 1-1.2 g/kg body weight/day. As long as required calorie intake is met, protein needs will likely be achieved. However, it may be useful to take protein supplementation to make sure all amino acids are ingested. 

 

 

Micronutrients

 

Fat Soluble Vitamins A, D, E, K

Aids immune function and bone metabolism. Found in oily foods, nuts, veg, dairy, whole eggs.

 

Water Soluble Vitamins B complex, C

Essential for energy metabolism, nervous function, muscle contraction, blood production, immune function. Found in fresh fruits, veg, cereals, animal products, whole eggs.

 

Iron

Needed for oxygen transport, energy metabolism, DNA production, blood production, immunity. A deficiency in iron is detrimental to health and performance. A female athlete is at greater risk of deficiency than others. Iron comes in two forms: haem and non-haem. Sources include meat, fish, nuts, tofu, and dark green leafy veg (spinach, broccoli). Iron supplements are recommended if vegetarian or if calorie intake is too low.

 

Calcium

Needed for weight bearing exercises to promote efficient bone repair and for slowing bone loss. Supplementation very useful for teenage girls if calorie intake is low. Found in dairy products, green leafy veg, and nuts.

 

 

Hydration

 

The key to water balance is understanding your input vs your output. Generally, we get 60% daily water intake is from fluids, 30% supplied from solid foods, and 10% produced within cells. Losses are from evaporation from skin and lungs, and excretion from kidneys and faeces.

 

If output becomes greater than input, then dehydration will occur. For athletes, the most common cause of dehydration will be from excess loss of sweat. Coupled with restriction of dietary water due to prolonged sessions and short intervals, urine volume will decrease and become more concentrated.

 

Varying degrees of dehydration are as follows:

 

1-2% body weight loss – Thirst, fatigue, weakness, discomfort, loss of appetite.

3-4% body weight loss – Impaired performance, reduced urine, dry mouth, flushed skin, apathy.

5-6% body weight loss - Difficulty concentrating, headache, irritability, sleepiness, impaired temperature regulation.

7-10% body weight loss - Dizziness, spastic muscles, loss of balance, delirium, exhaustion.

 

To put things into perspective for how dehydration negatively effects performance - every litre of water lost causes the heart rate to increase by 8 beats per minute, cardiac output to decline by 1 litre per minute, and core temperature to rise by 0.30C.

 

Rehydration is often misconstrued as it is not solely the replenishment of fluid in the body, but also the reuptake of lost principal solutes (potassium, sodium, chloride, ionic protein etc.) or electrolytes. Although the obvious choice to rehydrate is water, this may not be an efficient choice since water shuts of thirst before an athlete can properly rehydrate. Therefore, water alleviates thirst when hydration is not close to normal.

 

The most effective ways to prevent dehydration is for athletes to consume adequate amounts of properly formulated sports drinks. The benefits include encouraged voluntary fluid intake, stimulates fast absorption, promotes rapid complete rehydration, and improves performance.

 

To prevent dehydration, it is most effective to follow a plan of intake rather than relying on thirst. Start early and continue at regular intervals. For example, set alarm to drink 150-250ml for every 20-30mins.

 

Rapid & complete restoration of fluid and electrolytes is essential and is priority. It has also been reported that CHO containing drinks are useful in assisting with refuelling goals. Therefore, Lucozade Lite is the recommended choice of drink as it is low calorie, but contains enough sugar and electrolytes to return to normal hydration levels.

 

 

 

 

Recommended Reading

 

Soric, M., Misigoj-Durakovic, M., & Pedisic, Z. (2008). Dietary intake and body composition of prepubescent female aesthetic athletes. International Journal of Sport Nutrition and Exercise Metabolism, 18(3), 343-54.

 

Bartlett, J., Hawley, J, & Morton, J., (2015), Carbohydrate availability and exercise training adaptation: Too much of a good thing?, European Journal of Sport Science, 15:1, 3-12

 

Louise M. Burke, John A. Hawley, Stephen H. S. Wong & Asker E. Jeukendrup (2011), Carbohydrates for training and competition, Journal of Sports Sciences, 29:sup1, S17-S27

 

Volek, J., Noakes, T., & Phinney, S., (2015) Rethinking fat as a fuel for endurance exercise, European Journal of Sport Science, 15:1

 

Phillips, S., Moore, D., & Tang, J. (2007). A critical examination of dietary protein requirements, benefits, and excesses in athletes. International Journal of Sport Nutrition and Exercise Metabolism, 17 Suppl, S58-76.

 

Cohen, D. (2012). The truth about sports drinks. BMJ (Clinical Research Ed.),345(7866), E4737.

 

Shirreffs, S., & Sawka, M., (2011), Fluid and electrolyte needs for training, competition, and recovery, Journal of Sports Sciences, 29:sup1, S39-S46

 

Fogelholm, M. (1999). Micronutrients: Interaction between physical activity, intakes and requirements. Public Health Nutrition, 2(3a), 349-356.

 

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