Performance enhancement in perspective

There are countless nutritional products aimed at the sportsperson, which claim to have some performance-enhancing ability. These substances, called `ergogenic aids', theoretically improve performance to a point above that obtainable through a good training programme. Athletes are very susceptible to any claims for even the slightest improvement in performance, as fractions of a second could mean the difference between winning or losing.

Many ergogenic aids are basically expensive forms of proteins, minerals and vitamins. Their effectiveness is often unproven, based on folklore and reliant on the ignorance of the consumer (for example, substances such as Royal Jelly and wheat germ oil). On the other hand, some performance-enhancing principles are based on reputable scientific evidence that have been shown to improve performance in the laboratory (such as carbohydrate supercompensation - see overleaf).

However, it is interesting that even in cases where the supplement or _special diet has no physical basis, an athlete can sometimes gain purely psychological benefit from consuming something he or she believes in.

Proteins and amino acids

Although certain athletes may need an increased amount of protein, taking excessive amounts in the form of powdered or liquid supplements is unnecessary. Despite the claims of manufacturers, large quantities of protein will have no beneficial effects on muscle growth, strength or on performance. Any excess will simply be used as an energy source or stored as fat. In addition, kidney function may be hampered and dehydration caused as a result of taking in too much protein.

The supplements currently in vogue - especially among body builders and weight lifters - are amino acids, the 'building blocks' of proteins. The theory is that certain amino acids stimulate growth hormones. The increase however is slight and has no practical effect. Amino acids are not 'fat burners' or detoxifiers as has been claimed. Although tablets taken for this purpose are extremely expensive, the amount of amino acids in them is very small. In fact, a single egg contains far more than that found in seven or more amino acid tablets!

Vitamins and minerals

As mentioned earlier in this chapter, supplementing vitamins and minerals has no performance-enhancing properties in an athlete whose normal diet is not deficient. The effects of taking megadoses of certain vitamins may even impair performance.

Manufacturers and quasi-nutritionists have given certain substances vitamin status, although they are not scientifically classified as vitamins. For example, pangamic acid (otherwise known as vitamin B15) supposedly prevents various diseases, slows the ageing process and improves physical performance. None of these claims has been substantiated. Laetrile or vitamin B17 is a source of cyanide and has been banned. Other `pseudovitamins' are orotic acid (vitamin B13), bioflavenoids and vitamin B-T (or carnitine), all of which do not function as vitamins.

Carbohydrate loading

`Carbo-loading' is a phrase which has passed into common use. It has been proved scientifically that carbohydrate loading (otherwise known as carbohydrate supercompensation) is one of the practices which is effective in improving performance. It may be explained in the following way: Exercise which lasts for longer than 60-90 minutes is dependent on the amount of glucose available. Glycogen (glucose) stores in the muscle and liver are small, so enlarging them allows an athlete to continue exercising at a higher intensity for longer. A carbohydrate-loading programme increases the amount of muscle glycogen stored before you need to use it.

The best method of doing this is to gradually reduce the amount of training you do during the six days preceding an event and, during the final three days, eat a diet that is high in carbohydrate (500-600 grams per day). The extra glycogen stored in this way allows the athlete to continue exercising for longer.

Carbohydrates, fluids and sodium during exercise

It has been proved that supplying the body with carbohydrate during endurance-type exercise has a glycogen sparing effect which allows an athlete to exercise for longer. Many studies have been done in attempts to find a solution that will allow the maximum amount of water to be absorbed, while at the same time providing an optimal amount of carbohydrate. So far, it seems that a form of carbohydrate known as 'glucose polymers' has the best absorption rate. These are chains of glucose molecules linked together. A solution containing about 10 per cent carbohydrate in the form of glucose polymers supplies the most glucose to the body during exercise, and at the same time provides sufficient water replacement. (It is important to remember that a carbohydrate solution is only of benefit during prolonged exercise.)

Adding sodium to replacement fluids increases the concentration of the fluid. It was initially thought that this would hamper the absorption of the fluid, but the most recent findings suggest that the addition of a very small amount of salt (1-2 grams per litre) is in fact necessary for absorption.

Alcohol

Not surprisingly, it has been proved that alcohol has no beneficial effect on exercise. In reality alcohol is a depressant that slows reaction time, impairs muscle reflexes and disturbs coordination. In addition, it causes dehydration which interferes with fluid balance and has a negative effect on performance.

Caffeine

Some athletes use caffeine as a stimulant and to increase the amount of free fatty acids in the blood. Theoretically, more fat is then available to be used for energy, resulting in glycogen sparing (see above). However, an excessive amount of caffeine is necessary to produce this effect and, apart from the fact that a very high concentration of it in the urine can disqualify a competitive athlete, there are several other disadvantages to using caffeine in this way. The main one is that it has a diuretic effect, which results in increased fluid losses and a greater risk of dehydration. In addition, overconsumption of caffeine can result in headaches and nausea and it is therefore not advisable to use large doses of this stimulant in an attempt to enhance performance.

Other imposters

Royal jelly, wheat germ oil, ginseng, extracts of various herbs and numerous other products have all at one time or another been touted as performance-enhancers. The truth is, however, that the only possible effect most of these substances could have would be a psychological one.

How fibre affects the body

The whole subject of food residue is a complicated one because of the variety of indigestible compounds and the different ways in which they influence the digestive and absorption processes in the body. In the simplest terms, dietary fibre acts in the digestive tract by binding or absorbing water and other substances, thus causing 'bulking' of the contents of the gut. It influences the speed with which food moves through the various parts of the digestive tract. However, the ways in which fibre affects digestion, absorption and the movement of food in the digestive tract are diverse, far-reaching and not always well understood. To illustrate this, fibre in the diet may affect blood sugar levels, the production of bile, the transport of cholesterol in the body and your chances of developing colon cancer. It can even affect the hormonal responses to a meal.

A variety of factors influence the effect of a particular fibre or high- fibre food. The chemical composition of the fibre, its particle size, the age of the plant source and methods used in the processing of the food, all affect the physical properties of the fibre. It is these characteristics which account for the different functions of fibre in addition to its main effect of causing in^creased bulk formation in the digestive tract.

Fibre effects are also influenced by the total composition of the meal and the amount of fibre in it. Short-term effects - for example on the blood sugar level - can be seen immediately after a person has eaten a single high-fibre meal. Long-term effects, such as lowering of blood cholesterol levels, occur only after a regular and prolonged intake of fibre. The effect of fibre in the different parts of the digestive tract (stomach, small and large intestine) also differs and may vary between individuals.

Fibre and the diseases of affluence

As already mentioned, research on dietary fibre was initially stimulated by studies which showed that population groups who follow high-fibre diets suffer far less from the 'diseases of affluence' - the medical term used to describe degenerative diseases and disorders which have been linked to a prosperous Western lifestyle. Among these are colon cancer, appendicitis, gall stones, varicose veins and constipation. Their causes are many; what has been established is that a variety of environmental factors, including dietary habits, can trigger these diseases in people who are genetically 'vulnerable' to them. This explains why they tend to run in families and why some people, even though they follow a Western lifestyle, do not develop a particular disease.

Let's look at those diseases which are known to be associated with the amount of fibre in our daily diets:

Constipation

Constipation is probably one of the most common disorders in the world and is also the cause of other diseases (see diverticular disease and colon cancer below.) It can be defined as the relatively slow movement of unduly firm waste matter through the large bowel, which results in the infrequent passing of small, hard and dry stools - often accompanied by straining.

Including enough fibre in your diet prevents constipation in various ways. Firstly, fibre is not digested in the small intestine. It therefore moves to the large bowel where it has a bulking effect, increasing the volume of the bowel content. Because it binds water, fibre prevents the absorption of water from the large bowel to some extent, ensuring that the contents remain large in volume and soft in consistency. Fibre also stimulates the growth of microbes in the large bowel, which contributes to larger, softer stools. The larger volume in the bowel stimulates peristaltic movements and eases the process of defecation so that straining is not necessary. In addition, during the partial fermentation of fibre in the large bowel by microbial enzymes, substances such as methane and hydrogen gasses, water and the short-chain fatty acids are produced. There is now convincing evidence that these acids play an important role in maintaining a healthy bowel.

Diverticular disease

It is now recognised that constipation - and the resultant increase in pressure in the colon (large bowel) because of strained bowel movements - is the underlying cause of diverticular disease. In this disorder, small, blown-out pouches or sac-like swellings (diverticula) form in the wall of the colon and project into the abdominal cavity. Inflammation of these pouches is known as diverticulitis and may cause abdominal discomfort and pain.

Diverticular disease is very common in affluent societies, especially among elderly people. The treatment of constipation with high-fibre diets will not only help prevent the development of the disease, but will also improve - and may even 'cure' - an existing condition.

Colon cancer

Although the role of diet in the development of this disease is still unclear, some scientists believe that high energy and fat and low fibre intakes are important contributing factors (see Cancer - can Your Diet Make the Difference?, page 181). The way in which fibre may protect against colon cancer is probably very complex. It is thought that the rapid movement of a bigger volume through the large bowel shortens the bowel wall's exposure time to substances which may induce cancer (carcinogens).

Because of its bulking and water-binding effects, fibre dilutes the concentration of carcinogens in the gut. It may even bind these substances and help with their excretion in the faeces. New research has showed that butyric acid, one of the short-chain fatty acids produced from fibre fermentation in the large bowel, also protects the bowel against the development of cancer. In addition, changes in colonic pH as a result of the fermentation process may be of importance.