Caffeine

Caffeine has long been demonized for its role as a pick-me-up in coffee, tea and cola drinks. As with many other popular foods, these drinks have been assumed to be bad for you, based purely on their caffeine content. Being pleasant to consume didn’t help their cause. Caffeine also appears in guarana (Paullinia cupana), a Brazilian plant claimed to reduce stress and depression, and increase sports performance. It is a popular soft drink in Brazil where the guarana paste is mixed with carbonated water and sugar.

Most of our caffeine comes in drinks made from the coffee bean, tea leaf, kola nut and cacao bean in which caffeine occurs naturally. These plants contain caffeine and related compounds theophylline and theobromine in their leaves as natural insecticides. Being a central nervous system stimulant, caffeine can keep the brain alert. This is the basis for the morning cup of coffee.

Does caffeine have any benefit to the athlete?

Several recent studies show increases in adrenaline levels after caffeine consumption. The extra adrenaline is thought to be useful by improving alertness and reaction times. It may also enhance the use of fat as a fuel and thereby spare muscle glycogen stores. This means that the body should be able to exercise for longer. Not all researchers agree with this theory, as exercise alone makes the body more efficient at using fat. Any performance-enhancing effect might be due solely to its stimulant effect, making the brain more alert and focused on the event.

According to Dr Lawrence Spriet, University of Guelph, caffeine generally has a positive effect in endurance athletes. "There is no question that in certain well trained individuals, caffeine pre-race can cause the adipose tissue to release some of its fats, such that when you start the exercise there’s a little bit more fat floating around in your blood stream for your muscles. This allows you to use less glycogen in the very early stages of the exercise, which is rather important because you use a fair amount of your stored muscle glycogen in the early stages of the exercise". He goes on to warn that the caffeine effect is relatively small and it is not consistent between individuals.

Researchers have found that giving endurance athletes doses of 5-6 mg caffeine/kg body weight (350-420 mg in a 70 kg person) is a level that will improve performance. The consensus is that caffeine has an ergogenic effect in endurance sports in doses currently legal under the IOC doping regulations. Caffeine has little effect in short duration, high intensity sports. (There have been claims that supplemental carnitine has a similar effect to caffeine. There is no scientific evidence that this is the case).

Caffeine will have different effects on different people. It will depend on how much caffeine is regularly taken during the day, how well trained you are, the dose of caffeine you take before exercise and your genetics. In someone who has very little caffeine normally, two cups of coffee might give such a zing to the brain that it dramatically reduces performance. Someone else may find that exercise is easier and endurance is improved.

What is considered to be too much caffeine?

Of course, the excessive consumption of caffeine can cause increased urination, nervousness, upset stomach, tremors and irritability. Withdrawal, in those used to high caffeine intakes (500+mg/day), is associated with headaches, lethargy, irritability and muscle pains, which are relieved by a hot cuppa. Insomnia may occur at 1000 mg a day. Some have suggested that caffeine can raise your metabolic rate for a short time, thereby mildly assisting weight control. There is general agreement that a daily caffeine dose of up to 300 mg is not harmful to most healthy people.

As caffeine is a diuretic (i.e. makes you wee), it has been suggested that you don’t drink a caffeine containing drink before or during sport, because it will encourage fluid loss and dehydration. If you do have a caffeine drink in the two hours before sport, make sure you have an equal amount of water too. If the caffeine drink is taken just before sport, or during sport, don’t worry as it won’t increase urine production during sport. However, I don’t suggest you have caffeine drinks after sport as it may slow the rate at which you rehydrate. After sport, drink non-caffeine drinks before you enjoy a cuppa.

My advice is to give caffeine a try if you wish, but don't expect wonderful results, nor be disappointed if you don't feel so hot. Try a low dose first, say two cups of coffee/tea. One piece of research suggests that there is an effect even at such a low dose. Whatever you do, try it during training sessions before you try it at the big event.

The International Olympic Committee (IOC) has stated that the maximum permitted level of caffeine in the urine is 12 milligrams/litre. Above this amount is considered doping and will result in disqualification of the athlete. This urinary level will be achieved by taking about 500 mg caffeine (7 cups coffee) in a short time. Naturally, most readers are unlikely to run foul of the IOC.

Dr Lawrence Spriet believes that taking caffeine for its ergogenic effect is cheating.

"The IOC have set the allowable limit for caffeine to be quite high, so if you were to get caught with higher than normal amounts that must mean that you are doing it by other than normal means. You are taking incredible amounts of caffeine and that implies you are trying to gain an unfair advantage. If you want to be truly ethical I would say that it should probably be banned".

• Tarnopolsky MA. Caffeine and endurance performance. Sports Medicine 1994; 18 (2): 109-125
• Pasman WJ et al. International Journal Sports Medicine 1995; 16: 225-230
• Spriet LL. Caffeine and performance. International Journal of Sport Nutrition 1995; 5: S84-S99
• Wemple RD, Lamb DR, McKeever KH. Caffeine vs caffeine-free sports drinks: effects on urine production at rest and during prolonged exercise. Int J Sports Med 1997; 18: 40-46
• Brouns F, van der Vusse GJ. Utilisation of lipids during exercise in human subjects: metabolic and dietary constraints. Br J Nutrition 1998; 79: 117-128
• Spriet L. Personal communication August 1999

Caffeine content of selected foods

Note: there is a large variation in the caffeine content of teas and coffees due to variety of bean or leaf, the processing method and infusion times.

• Food Technology, April 1983, p87
• Supplement to Food Technology in Aust, January 1988, piii
• Caffeine Survey 1995. Western Australian Food Monitoring Program. Health Dept WA 1995