Guidelines on the optimal amount and types of fluid to consume to achieve fluid balance are widespread, though it is typically recommended that we drink 2 litres of fluid a day, mostly as water.

Some specific recommendations suggest limiting consumption of caffeinated beverages, including coffee, as it may negatively impact overall fluid balance. Interestingly, existing scientific evidence does not support this ‘common knowledge’ recommendation on coffee and more research is needed before any firm conclusions can be drawn.

No evidence of any detrimental effects of caffeine on exercise performance

A 2002 review of the literature on caffeine and fluid balance during exercise concluded that a daily intake of 300mg of caffeine (the amount found in approximately 3 regular cups of coffee) may act as a mild, short-term diuretic. This effect is similar to that of water, with no significant effect on overall fluid balance. Additionally, the authors found no evidence for any detrimental effects of caffeine on hydration during exercise in hot climates. They concluded that advice to avoid caffeinated beverages before, and during, exercise are not supported.

A more recent survey found no effect of moderate levels of caffeine on dehydration, either at rest or during exercise, and suggests that similar conclusions can be drawn for caffeine’s long-term effects.

In an interview, available to view here, Dr Andrew Blannin from the School of Sport and Exercise Sciences, at the University of Birmingham in the UK explains:

“There is no evidence of any significant detrimental effect of moderate caffeine consumption on sports performance, nor is there any evidence that caffeine consumption adversely effects hydration status or ability to regulate body temperature during exercise.”

Caffeine beneficial in endurance exercise

The evidence shows that caffeine ingestion in moderate quantities is beneficial for sports performance for endurance athletes. Also, a 2010 review does not support claims that caffeine induces urine production during exercise.

Dr Andrew Blannin states:

“In 2011, EFSA concluded that caffeine was indeed an ergogenic aid and that’s because it’s been shown to improve endurance performance, endurance capacity and ratings of perceived exertion…Performance benefits can be seen with moderate intakes of coffee, so 3mg per kg of body weight which is equivalent to 2-3 regular cups of coffee.”

Caffeine does not adversely affect temperature regulation

Several factors can reduce our tolerance for heat during exercise in hot environments. Reviews of the effects of caffeine show no evidence that caffeine leads to chronic dehydration, or negatively affects temperature regulation, in hot environments.

Dr Andrew Blannin states:

“Factors such as temperature, humidity and exercise levels will affect our fluid requirements. Although we are working on a large scale study to provide conclusive evidence, the majority of the literature suggests that moderate consumption of coffee, about 3-4 cups of coffee a day, can contribute to our daily fluid requirements.”

For more information on coffee and sports performance, coffee and fluid balance and to view reference materials, click here.

Also, to see Dr Andrew Blannin discuss the latest research on the relationship between coffee consumption; sports performance and fluid balance with Dr Trisha Macnair, hospital physician and health journalist view our vodcast here.

Potential mechanisms

Until recently, the ability of caffeine to enhance performance was thought to be due to its effect of increasing levels of circulating free fatty acids in the body. This is because it helps spare muscle glycogen stores as the fatty acids are used for energy. However, several other mechanisms are now being investigated.

Caffeine may increase adrenalin production in endurance sports

Recent research has found that caffeine affects endurance performance via a pathway that leads to an increased production of adrenalin. This then stimulates energy production and improves blood flow to the muscles and the heart. Caffeine may also alter fatigue and influence ratings of exertion, perceived pain and energy levels, all of which are likely to lead to improvements in performance.

Caffeine’s effects on anaerobic exercise still under investigation

A recent review has found that current theories on caffeine do not wholly account for its effect on short-term anaerobic exercise.

As more studies are carried out, it appears that the understanding of mechanisms behind the effects of caffeine on both aerobic and anaerobic exercise seem to be moving in the same direction. Research to date suggests that the adenosine antagonist is the most likely mechanism behind the effects of caffeine. This is a pathway that leads to an increased production of adrenalin, which stimulates energy production and improves blood flow to the muscles and heart.

For more information on coffee and sports performance, and to view information sources, click here.

Caffeine and performance in endurance (aerobic) exercise

It has been shown that caffeine can improve performance in individuals taking part in endurance-type, aerobic exercise.

In an interview, available to view here, Dr Andrew Blannin from the School of Sport and Exercise Sciences, at the University of Birmingham in the UK explains:

“The beneficial effects of coffee on sports performance are due to the caffeine within the coffee. In 2011, EFSA concluded that caffeine was indeed an ergogenic aid and that’s because it’s been shown to improve endurance performance, endurance capacity and ratings of perceived exertion. Performance benefits can be seen with moderate intakes of coffee.”

Caffeine linked to faster times in endurance races

A recent review in which subjects had to run, cycle or row a set distance saw faster times recorded in individuals who consumed caffeine. This effect was seen in individuals taking moderate quantities of caffeine before and/or during exercise.

Caffeine may help reduce muscle pain

Muscle pain during exercise can impede performance. Caffeine ingestion of 5mg/kg body weight has been found to reduce muscle pain for a group of subjects carrying out 30 minutes of high-intensity cycling, compared to another group who had not consumed any caffeine.

Caffeine and performance in short-term high-intensity (anaerobic) exercise

Although there is some evidence pointing to positive effects of caffeine on short-term high intensity exercise, there is a wide variation in results between studies. EFSA does not currently consider there to be sufficient scientific proof to support a set position.

Caffeine appears to improve performance in specific individuals

Studies in high intensity, anaerobic exercisefound the effects of caffeine to be more evident in certain groups of people involved in specific sports. These could include trained athletes engaging in power-based sports, team sports, and sports requiring intermittent bouts of activity. Additionally, a moderate amount of caffeine was more effective than a high dose.

Caffeine and sports aids may have an additive effect

A recent study found that when caffeine was given to subjects playing a simulated soccer match, as well as a carbohydrate-electrolyte sports drink, there was a significant improvement in short distance sprinting and jumping in the group who consumed caffeine as well as their sports drink.

The effects of caffeine appear to be time-limited

Two trials looking at anaerobic exercise repetition in trained and active people reported that the ingestion of caffeine produced an improved performance in the first set of exercises, but not in the second set. This suggests that the effects of caffeine are only short-term.

For more information on coffee and sports performance, and to view information sources, click here.

Also, to see Dr Andrew Blannin, School of Sport and Exercise Sciences, University of Birmingham, UK, discuss the latest research on the relationship between coffee consumption; sports performance and fluid balance with Dr Trisha Macnair, hospital physician and health journalist view our vodcast here.