Supplementation

Vitamins/Minerals

Vitamins are a group of micronutrients that are only required in small amounts, and do not provide any energy in the form of kilojoules or calories. Although vitamins don’t directly provide any energy, many vitamins play essential roles in the breakdown and metabolism of macronutrients (fats, carbohydrates, protein and alcohol) to produce energy. As well as their involvement in energy-production pathways, vitamins also play a key role in the building and repair of tissue and immune function.

The majority of vitamins are essential, as they are unable to be synthesised by the body, and therefore must be provided through a balanced diet. There are two groups of vitamins: fat-soluble vitamins (vitamins A, D, E and K) and water-soluble vitamins (all B vitamins and vitamin C). Minerals are also essential micronutrients for optimal health and sports performance. Like vitamins, minerals do not provide energy. Key minerals include calcium, iron, magnesium, sodium, potassium, zinc, iodine and selenium. Iron and calcium are two key minerals that are often deficient among certain athlete groups.

Calcium is integral for bone structure, and also plays a role in muscle contraction. The development of strong bones occurs during childhood and adolescence. An adequate calcium intake, vitamin D status and regular weight-bearing exercise all contribute to the development of healthy bones. If these factors are not accounted for, the risk of fractures, osteopenia and osteoporosis is significantly increased in later life. The quality (density) of bone tissue gradually declines from the mid-twenties in both males and females, and even greater losses occur after menopause in females. Recent national surveys in Australia have identified that calcium intakes of children and adolescents are well below the recommended dietary intake (RDI) levels. Among this age group, there are also decreasing rates of physical activity; combined with a low calcium intake, this is a key risk factor for poor bone health later in life.

Calcium-rich foods include dairy products, green, leafy vegetables and fish with edible bones such as sardines and canned salmon.

Iron is a key component of haemoglobin, which is responsible for the transport of oxygen around the body. As well as having a significant impact on general health, low iron will negatively affect sports performance due to reduced oxygen delivery to working muscle. As a result, the muscle cells are unable to produce energy and eliminate acidic by-products effectively. Those most at risk of iron deficiency are females, vegetarians and endurance athletes (they have higher sweat losses). Athletes competing in low-weight category events (such as lightweight boxing and rowing), or events where having a low body weight is an advantage, are also at risk due to restricted food intake among these athletes.

Foods high in iron include lean meats, green leafy vegetables, legumes, wholegrain products and fortified products such as breakfast cereals.

Sports anaemia is a condition experienced by many athletes – particularly during periods of heavy training – and presents as general lethargy and fatigue. This condition is not a true iron deficiency, as it is typically not the result of low iron intake but rather due to significant increases in training load and training adaptations such as increased blood volume. Provided there is an adequate dietary iron intake, sports anaemia will generally resolve with the gradual tapering of the training load.

Many athletes choose to supplement their diet with additional vitamins and minerals on top of their dietary intake, believing it will aid performance and recovery. Despite their widespread use, there is no clear evidence that general multivitamin supplements improve performance, and the absorption of these vitamins and minerals from a supplement is generally much lower than from eating the foods that contain them. Some research has indicated that these supplements may even prevent the development of certain training adaptations, and therefore may have a negative effect on performance.

Recent research indicates that certain nutrients may improve performance – for example, specific nutrients in beetroot may improve performance in sprint cycling events and power-based sports and magnesium may aid muscle recovery; however, more research is needed to confirm this and identify what the optimal dosage is to achieve these benefits.

Protein

Protein is important for the building and repair of new tissue, and as a result many athletes competing in strength and power sports take additional protein supplements as they believe it will help increase their muscle mass. Proteins are made up of a range of different amino acids, and a range of different supplements are available in liquid or powder form. It is important that athletes are educated about protein, as it is not used to fuel exercise performance (this only occurs under extreme conditions when carbohydrate and fat stores are exhausted). As protein is not a fuel, the majority of athletes easily meet their protein requirements through their food intake without needing additional supplements. Despite this, many athletes still consume excess amounts of protein, and intakes of around 3 grams per kilogram of body weight are not uncommon among certain athlete groups – especially in male team sport environments. Historically, there has been concern that high-protein diets may have a negative effect on kidney function; however, there is no widespread evidence among healthy athletes to support this.

An important consideration regarding an athlete’s protein intake is how they spread it out over the day. Recent studies have shown that strength gains, muscle hypertrophy and recovery are improved with small amounts of protein (15–25 grams) consumed regularly throughout the day. Many athletes do not evenly distribute their protein intakes, and typically have small amounts at breakfast and snacks and large amounts at the evening meal. Protein supplements/shakes can be attractive to athletes as they are portable and convenient to consume in between meals and after training sessions. The recommended serving size on many of the protein powders available may be as high as 50–60 grams of protein per serving, which is significantly more than required.

Caffeine

Caffeine is a substance found naturally in the leaves, beans and fruits of a variety of plants, and is regularly consumed by some 90 per cent of adults. The most common dietary source of caffeine is coffee, but cola drinks, energy drinks and specialised sports foods and supplements also contribute to regular intake.

Caffeine is rapidly absorbed and transported to all body tissues and organs, where it has a large variety of effects. These may vary between individuals, and can be both positive and negative responses, including the mobilisation of fats to the muscle cells, changes to muscle contractility, alterations to the central nervous system to change perceptions of effort or fatigue, stimulation of the release and activity of adrenaline, and effects on cardiac muscle.

The major benefits of caffeine on exercise capacity and performance appear to be achieved by central nervous system effects. These effects reduce the perception of fatigue and allow for optimal pacing and performance to be maintained for a longer period. This is most likely to benefit endurance sports such as long-distance running, cycling, triathlons and cross-country skiing.

In the past, caffeine has not been recommended among athletes due to its potential to act as a diuretic and contribute to dehydration. More recent studies have shown that small to moderate doses of caffeine have minor effects on overall hydration in people who are regular caffeine users. In addition, caffeine-containing drinks such as tea, coffee and cola drinks provide a significant source of fluid in the everyday diets of many people, including athletes.

Sports supplements and ‘pre-workout’ supplements are not required to list their caffeine content on the label. For example, several supplements do not list their caffeine content; however, caffeine (methylxanthine) or guarana – which contains caffeine – are listed as ingredients. Supplements are not subject to the same criteria as foods, and therefore they may contain significantly more caffeine per serve than common foods and drinks. This is a concern, as many of the ‘pre-workout’ supplements are popular among young athletes who may not be habitual caffeine users.

These sources also show that there are a variety of protocols of caffeine intake that can enhance performance. These include the consumption of caffeine:

• before the exercise bout

• spread throughout exercise

• taken late in long-duration exercise as fatigue is beginning to occur.

Different protocols may achieve optimal performance outcomes, even in the same sport or individual. Suitable or optimal protocols may be dictated by the specific characteristics of the event, the practical considerations of consuming a caffeine-containing product and the individual characteristics/preferences of the athlete. The athlete who is intending to use caffeine to enhance sports performance should experiment in training or less important events to determine the timing and dosages of caffeine that best suit their individual needs.

Creatine Products

Creatine is a naturally occurring compound found in large amounts in skeletal muscle and the brain. Creatine is provided from dietary intake and synthesis from amino acids. The major source of creatine in the diet is from animal muscle – such as meat or fish – which typically provides 1–2 grams per day, or half the daily turnover. As vegetarians do not consume any significant creatine in their diets, they are reliant on the body making creatine from amino acids, and typically have lower creatine levels in their muscles. Creatine provides a number of important functions related to fuel supply in the muscle. The best-known role is as a source of phosphate to regenerate ATP, which is the most important fuel source for sprints or bouts of high-intensity exercise lasting up to 10 seconds.

Studies in the early 1990s showed that muscle creatine and phosphocreatine in skeletal muscle could be increased by around 20 per cent. These results are significant in terms of improving the exercise capacity of the phosphocreatine energy system, and have led to the widespread use and popularity of creatine among a range of athletes. Since then, further studies have shown that there is considerable variability in different athletes’ responses to creatine supplementation. Individuals with the lowest initial levels, such as vegetarians, may show the greatest responses, while individuals with higher resting creatine levels may not significantly benefit from supplementation.

Strategies that enhance creatine uptake into the muscle cells include taking creatine with a carbohydrate-rich meal or snack (around 50 grams of carbohydrate). Creatine supplementation has been shown to enhance the performance of exercise involving repeated sprints or bouts of high-intensity activity, separated by short recovery intervals. Therefore, competition or training programs involving intermittent high-intensity work patterns with brief recovery periods (less than 1 minute) or resistance training programs are most likely to benefit from creatine supplementation. Performance enhancements may be seen as the result of an acute loading protocol, but chronic creatine use may offer the greatest benefits.

The best-researched dietary creatine supplement is creatine monohydrate, with a number of protocols of loading being established:

• Rapid loading may be achieved by five days of repeated doses (e.g. five doses of 5 grams) of creatine.

• Slow loading will occur over a longer period (28 days) with a daily dose of 3 grams.

• A maintenance dose of 3 grams per day will allow elevated levels to be sustained.

• Unloading: once the muscle creatine content has been saturated, it will take at least four weeks to return to resting levels.

A weight gain of 600–1000 grams is typically associated with acute loading, and is due mostly to water retention.

Creatine monohydrate is the common source of creatine in commercially available supplements, and the experience of 20 years of research indicates it is safe and effective in the recommended dosages. A number of other forms of creatine have been included in newer supplements, with claims of being a superior form of creatine; these include creatine serums, creatine malate and creatine ethyl esters. There is little to no evidence supporting marketing claims that these alternative creatine sources are more effective in increasing muscle creatine levels and achieving performance outcomes, or that they are associated with fewer side-effects.

Creatine supplementation should be limited to experienced and well-developed athletes. Young athletes are able to make substantial gains in performance through maturation and skill/technique improvements without supplementation.