The IOC consensus statement on sports nutrition 2003 states that. ‘The amount, composition and timing of food intake can profoundly affect sports performance. Good nutritional practice will help athletes train hard, recover quickly and adapt more effectively with less risk of illness and injury’.

It is therefore essential that all athletes have the appropriate information to make the right food choices and that all support staff encourage optimal nutritional practice both during training and competition.

The use of dietary supplements to achieve optimal intake is generally not required unless the dietary intake has been shown to be deficient in a specific nutrient e.g. iron or calcium etc. This may be identified by the doctor using blood tests or by the dietitian through a dietary assessment. Recommendations would be given to the individual at the time regarding the need for supplementation.

It is possible to achieve an adequate intake of vitamins and minerals by eating a well thought out diet and in fact taking excessive amounts of vitamins and minerals in the form of supplements can be detrimental to health e.g. mega doses of vitamin C can cause diarrhoea, nausea and stomach cramps. Despite this, many athletes are tempted to take dietary supplements, particularly as supplement manufacturers advertise their products with claims of improved performance.

However most companies do not invest in research and so real proof of their claims is usually impossible to obtain. Supplement manufacturers are not regulated in the same way as medicine manufacturers and so contents listed on the label may not be a true reflection of what they actually contain. 

If athletes do take supplements, doing so may increase the risk of a positive drugs test, as there is the risk that such supplements could be contaminated with banned substances. This is known to be the case as many athletes have been tested positive through the use of such supplements and from the results of a study published in April 2002 (see below for details). However choosing pharmaceutical grade products may reduce the risk of inadvertently taking a contaminated or poorly labelled product.

This study looked at 634 nutritional supplements and 94 out of these samples (14.8%) contained substances, not listed on any, that would have led to a positive drugs test. Out of the 94 samples, 23 contained precursors of both nandrolone and testosterone, 62 contained precursors of testosterone alone and 7 contained precursors of nandrolone alone. In addition to these 94 samples, 66 others (10.4%) returned bordeline results for various unlabeled substances.

The 634 supplements were gathered from 215 different providers in 13 countries from October 2000 to November 2001. 91% of them were bought in store or over the Internet. The rest came from the manufacturers. The IOC accredited laboratory in Cologne, Germany tested all supplements. Of the 37 samples tested from the UK18.9% were positive. In addition to this the Austrian Federal Ministry for social security and public welfare carried out similar tests on 54 supplements and found that 22% contained banned substances. As a results of these studies a position statement was released in May 2003 on behalf of UK sport, the British Olympic Association (BOA), the British Paralympic Association (BPA), National sports medicine institute (NSMI), and the Home County Sports Councils (HCSC)

‘UK athletes are advised to be extremely cautious about the use of any supplements. No guarantees can be given that any particular supplement, including vitamins and minerals, ergogenic aids, and herbal remedies, is free from prohibited substances as these products are not licensed and are not subject to the same strict manufacturing and labelling requirements as licensed medicines.

Antidoping rules are based on the principle of strict liability and therefore, supplements are taken at an athlete’s risk and personal responsibility’

This statement reflects the current state of the supplements market and all hockey players should be aware of the risks involved in taking supplements and should be discouraged from doing so. If a specific need for a supplement is identified, this should be discussed with the doctor and dietitian.

To get supplements tested for purity by a reliable laboratory is very expensive and does not provide a guarantee to the safety of the supplements. It would not be sufficient to just test one bottle of supplements to see if it was safe. Each batch would have to be tested to ensure it had not been contaminated. This is not currently an option available, so there is no way of telling whether a supplement is safe or not.

Some of the commonly available and popular supplements are listed below. Remember these products are not licensed and are not subject to strict regulatory and licensing requirements regarding labelling of constituent substances and manufacturing that licensed pharmaceutical products are. They may therefore contain prohibited substances

Vitamins and minerals may contain prohibited substances and so are not advised. However athletes determined to take them despite the warnings should ensure they only buy reputable brands, check the label and seek advise first from their sports dietitian or doctor.

There are many varieties of ginseng and it is claimed that some forms can affect the CNS having a stimulant like effect reducing fatigue as well as claims to improve concentration, immune function and slow the aging process. There is no conclusive evidence that ginseng has any benefit to sporting performance. There have been instances were products named ginseng have contained prohibited substances such as ephedrine, anabolic steroids etc

Ma Huang is a Chinese herb extract that contains several ephedra alkaloids including the banned substance ephedrine. It is a common ingredient in many dietary supplements that are promoted to increase energy or assist with weight loss. Many reports have documented adverse effects in people taking ephedra such as high blood pressure, insomnia, tachycardia, nervousness, tremors seizures, cardiac arrest, stroke and death. A potentially dangerous substance to be avoided.

Creatine supplementation is thought to be beneficial to competitors who compete in sports requiring short burst of maximal effort (e.g. weight lifting or sprinting) or repeated bursts of short, high intensity activity. It is not know how long creatine can safely be taken for, and there are several potential side effects. The European commission scientific committee on food has concluded that high doses of creatine should be avoided and that consumption of lower doses (up to 3g.day) are unlikely to pose any risk to health. However, some creatine supplements have been found to contain banned substances and so the same advice should be adhered to as other supplements discussed.

Amino Acids make up the structure of protein and are popular supplements with body builders. It is possible to eat sufficient protein through dietary means to enhance muscle mass development without the use of such supplements. There is no evidence that the use of Amino acids will enhance performance and the risk of contamination with banned substances is the same as with other supplements

Caffeine was removed from the banned substance list in January 2004. It does however remain on the monitoring programme and will be monitored to detect patterns of misuse in sport. It may be added to the prohibited list again if it is found to be misused.

Caffeine when taken 1-3 hours before exercise can improve performance in both endurance and high intensity exercise.

The likely mechanism is via the central nervous system (CNS) and effects include altered perception of fatigue and effort. It may also improve alertness, reaction time and attention span. Caffeine may also have direct effect on the muscle. Caffeine may increase the mobilisation and utilisation of fatty acids, leading to a sparing of muscle glycogen. This however this is thought to be the less likely mechanism to explain its effect on sports performance.

Benefits occur at modest levels  - 1-3mg caffeine/kg body weight, when taken before and/or during exercise. This is a lower dose than has been quoted in the past (6-9mg/kg has been used) and is a result of recent research (Cox 2002). There is not a dose response relationship so increasing dose will not provide further benefit.

The effect of caffeine differs between individuals. Some individuals do not respond and others may experience negative side effects such as tremors, increased heart rate and headaches. These side effects are more common at higher doses i.e. 6-9mg caffeine /kg

Other side effects caused by taking too large a dose include nausea, irritability, diarrhoea, insomnia, trembling and nervousness. More severe side effects include peptic ulceration, delirious seizures, coma and superventricular and ventricular arrhythmias. A condition known as known as caffeinism has been described by Greden, characterised by symptoms including anxiety, mood changes, sleep disturbances and psychological changes. People with such symptoms may experience withdrawal symptoms. Excessive doses of caffeine, up to 10g can be lethal, causing seizures, tachycardia, or ventricular dysrrythmias.

Taking caffeine 5-10mins before exercise may have an effect on performance as it enters the blood stream quickly. However if caffeine is taken 1 hour before exercise it will have time to reach max concentration in the blood and so the effects may be greater.

High doses – above 300mg will have a diuretic effect, and may affect hydration status. Hence it is important to keep the intake below this.

Taking 1-3mg/kg about 1 hour before training would be sufficient to have a performance enhancing effect. E.g. if an athlete weighs 70kg a dose of 70 – 210mg caffeine would be sufficient. Taking caffeine on a regular basis can be habit forming and so if athletes choose to take it should use it sensibly.

Please see separate sheet on caffeine for more detailed information

Pseudoephedrine has been removed from the prohibited list of substances, but ephedrine is still prohibited. Pseudoephedrine like caffeine, remains on the monitoring program. Pseudoephedrine is a central nervous system stimulant and therefore is potentially open to misuse.

Pseudoephedrine is available in over the counter medications and is principally used as a decongestant in preparations such as cold remedies. It exerts is effect through stimulation of á –1 adrenoreceptors in vascular smooth muscle, leading to vasoconstriction and a decrease in mucus secretion.

It also causes stimulant effects to the central nervous system and so may increase alertness, decrease fatigue levels and increase competitiveness and aggression. 

Possible side effects of these over the counter remedies include headache, tacycardia, dizziness, hypertension, irritability, sleep disturbance and anxiety.

They may also make it difficult for an athlete to cool down, particularly after exercising for long periods of time. At high dose they could cause mania or psychosis. Severe effects could also include cerebral haemorrhage and stroke.

It must be remembered that ephedrine is still a prohibited substance so ingredient lists should be carefully checked and advice sort from the Doctor, or anti doping officer if athletes are unsure.

Exercise performance can be impaired by 10-20% if dehydrated by as little as 2% of body weight.  Fluid losses in excess of 3% increases the risk of heat cramps, heat exhaustion or heat stroke.  Dehydration can affect mental function, slowing reaction-response times and decision making skills, which are vital in team sports.

Fluid loss depends on sweat rates and can vary between 500-2000ml per hour depending on environmental temperature. Fluid should be replaced during exercise preferably at a rate equal to sweat rate. It is important not to over consume fluids as this may potentially cause the problem of hyponatremia.

All athletes should know their sweat rate and aim to consume sufficient fluid during each training session/game to match fluid losses.
 
To calculate sweat rate:

Record pre training weight (kg) in minimum clothing
Record post training weight (kg) removing sweaty clothing first
Subtract post training weight from pre training weight to obtain weight lost – convert kg to g’s i.e. multiply by 1000. For example if weight loss is 1.2kg this would be 1200g
Record the amount of fluid (ml) consumed during training i.e. weigh drinks bottles before and after training, noting any refills
Record volume of any urine (ml) passed during that time (this volume will only be subtracted if urine was passed prior to post exercise body weight)
Record the length of time spent training in hours
SWEAT rate ="(Pre" exercise body weight – post exercise body weight) + fluid intake – urine volume, Exercise time in hours

1 kg weight loss equates to 1 litre fluid loss
For every kg of weight lost, 1.25 -1.5litres fluid is needed to replace it due to the continuing loss of sweat after exercise finishes and the urine losses that persist even in the dehydrated state. This will ensure optimal hydration is achieved after the event.

Athlete A should therefore consume just over 1 litre per hour to keep up with sweat rate and maintain a good hydration status

During exercise, fluids should be replaced at a rate equal to sweat rate, which will vary depending on exercise intensity, temperature, humidity, hydration status, acclimatisation and the type of clothing worn.

Athletes should aim to start training in a fully hydrated state. During the day, hydration should be maintained by drinking water, fruit juices, squashes etc. Excessive amounts of tea and coffee should be avoided.

500 - 600ml water or sports drink (to maximise glycogen stores) should be consumed 2 –3 hours before exercise and then 200-300ml 10-20 minutes before exercise. Sports drinks are useful before exercise if carbohydrate intake during the day has not been optimal or if there has been a long gap between the last meal/snack and the training session or if the session will be high intensity.

During training, 200-300ml fluids should be consumed every 10-20 minutes. These are general guidelines but individual requirements should be calculated to avoid under or over hydration
After training the fluid required to replaces losses should ideally be consumed within 2 hours to ensure that optimal hydration is achieved as soon as possible in case a further event is imminent.

The post exercise rehydration drink should contain carbohydrate to help replace glycogen stores and sodium to help conserve water and encourage the drive to drink (i.e. an isotonic or hypertonic sports drink).

Keeping the volume of fluid in the stomach at 600ml or more facilitates faster emptying and absorption from the stomach and into the blood stream so hydration can keep pace with sweat loss.

It is important that athletes take fluid on board for any exercise lasting over 30 minutes.

Water may be sufficient for low intensity exercise up to 45-50 minutes. For higher intensity exercise of 45-50mins where fluid losses are greater a sports drink would be of benefit.

An intake of 1g carbohydrate per minute maintains optimal carbohydrate metabolism – for example 1 litre of a 6% carbohydrate drink per hour of exercise. Generally athletes should choose an isotonic (5-8% carbohydrate) sports drink unless training in very hot climates where large quantities of fluid are required in which case a hypotonic (1-3% carbohydrate) sports drink may be more appropriate.

30-60g carbohydrate per hour in the form of a sports drink will maintain energy levels and enhance performance. Preventing low blood glucose levels by consuming a sports drink can also be beneficial to immune system function.

Cold fluids encourage greater consumption so a temperature of 10-15 degrees centigrade is recommended for fluids.

Sports drinks are fluids containing carbohydrate and electrolytes. The carbohydrate is usually a mixture of glucose, sucrose, fructose and maltrodextrins (glucose polymers which are glucose units linked together). High concentrations of fructose (>10%) can cause gastric upset and decrease water absorption. The amount of fructose in a drink should be no more than 2-3g/100ml (2-3%).

The electrolytes added are sodium and sometime potassium and magnesium.  Glucose absorption requires the presence of sodium and is an active process, so the addition of sodium stimulates glucose and water absorption. The provision of 22-30mmol (506 - 690mg) sodium per litre fluid would be appropriate to replace most of the sodium lost from sweating whilst at the same time remaining palatable. Sweat contains 40-80mmol sodium/l.

Drinks containing 5-8% glucose or sucrose are absorbed into the body more rapidly than water and also provide some energy. A slightly higher concentration of carbohydrate can be used if the carbohydrate source is a glucose polymer or maltodextrin, without decreasing the rate of stomach emptying.

An isotonic drink has the same number of dissolved particles as are found in plasma (about 290mosmol per kg). The dissolved particles are electrolytes and carbohydrates such as glucose or glucose polymers. Isotonic drinks promote water and carbohydrate absorption.

A less concentrated drink containing 1-3% carbohydrate (hypotonic) has a lower osmolality and promotes water absorption but provides less carbohydrate energy.

Drinks with a higher osmolality, usually >10% carbohydrate energy, are hypertonic and slow gastric emptying thus decreasing fluid absorption. These more concentrated drinks are useful as recovery drinks after exercise. They can also be used in situations when provision of fuel takes priority over fluid replacement.

The composition of the powerade that will be available for the Olympic games has been modified to contain 40g carbohydrate and 40mmol sodium per litre. This is to reflect the increase in sweat rate and therefore sodium loss in a hot climate and is closer to the actual composition of sweat than most sports drinks. The lower carbohydrate content is to take into account the fact that a greater fluid volume will need to be consumed and so prevents excessive carbohydrate being taken on board during exercise (30- 60gcarbohydrate per hour is the optimal amount to consume during exercise)

It is important that athletes monitor their own hydration status. They should be aware of the symptoms of dehydration, of how to use urine volume and colour as an indicator of hydration status and the importance of pre and post body weight measurements.

Signs and symptoms of dehydration include thirst, irritability, and general discomfort, followed by headache, weakness, dizziness, cramps, chills, vomiting, nausea, head or neck heat sensations and decreased performance

Thirst is a poor indicator of the need to drink to drink. Thirst indicates that 1.5-2.0l fluid have already been lost

The ‘pee’ test. When fully hydrated large amounts of very pale yellow urine will be passed. Numbers 1-3 should be the aim. Dark yellow urine is an indication of dehydration although vitamin supplements containing riboflavin will colour the urine dark yellow.

As discussed pre and post training weight can be used to calculate fluid losses. As a minimum, aim for a body weight change of less than 2%.

Other tests that can be done in the field include urine specific gravity.

This is done using a refractometer and should be done using mid stream urine. This can be performed by the physiologist or dietitian and gives a figure, which correlates to hydration status. See chart below.

Indexes of hydration status
Condition % Body weight change Urine colour Urine specific gravity

Well hydrated +1 to –1 1 or 2 <1.010
Minimal dehydration -1 to –3 3 or 4 1.010 – 1.020
Significant dehydration -3 –5 5 or 6 1.021 – 1.030
Serious dehydration >5 >6 >1.030

% Body weight change ="(Pre" exercise body weight – post exercise body weight)  x 100
Pre exercise body weight

A condition called hyponatremia can occur in athletes who consume excessive amounts of fluid or who drink low sodium fluids. It is defined by low blood sodium levels less than 130mmol/l.

Hyponatremia occurs most frequently in sports lasting longer than 4 hours, during lower intensity endurance activities, when athletes drink large volumes of water without adequate sodium intake.

Signs of hyponatremia are similar to those of heat stroke such as nausea, vomiting, extreme fatigue, respiratory distress, and central nervous system disturbances (i.e. dizziness, confusion, disorientation, coma and seizures). It also has unique characteristics such as low plasma sodium levels. Other symptoms may include worsening headache, normal exercise core temperature (generally not > 104ºF), swelling of the hands and feet. If hyponatremia occurs medical help should be sought.

Athletes should be aware of the fluid replacement guidelines and should not replace fluids in excess of sweat losses. They should have access to sports drinks containing sodium, monitor body weight and aim not to gain weight during a training session. Consuming a little extra sodium during meals and snacks during continuous days of training in a hot climate will also help maintain blood sodium levels.

Sweat rate increases after 10-14 days of heat exposure, so fluid intake should be increased accordingly using pre and post weights to calculate sweat rate as previously discussed

General guidance for fluid replacement in the heat during training is 750-1250ml of sports drink per hour but this should be adjusted for individuals

Increase sodium intake during the first 3-5 days of heat exposure as there is an increase in the amount of sodium lost in sweat

After 5-10days the sodium concentration of sweat decreases and normal sodium intake is sufficient.

If homemade sports drinks are used rather than commercial varieties then salt should be added to these (1/4tspn -1.25g per litre) to ensure salt losses are replaced. This would equate to 500mg sodium (sodium x 2.5 ="salt)."

To prevent taking on board excess carbohydrate, hypotonic (1-3%) sports drinks may be more appropriate during exercise in the heat.

Keeping fluids chilled will encourage a greater intake.

Be aware of signs of dehydration and heat illness such headaches, nausea, vomiting, weakness, dizziness. Confusion/disorientation and irrational behaviour can occur with heat stroke.