Alcohol use and athletes - facts and physiology

article by sports dietitian Clare Wood

There has long been a strong association between alcohol and the world of sport. With alcohol being linked to celebrations, there is no doubt that many athletes are going to have a few drinks after winning a major championship or weekend game, or even after finishing a distance run with a PB. Some research shows that athletes are higher consumers than non-athletes, and this could often be binge drinking rather than moderate drinking, as they will abstain from drinking during training periods, only to let loose on the other side of competition.

Moderate drinking can have some benefits on athlete health, such as reducing the risk of heart disease by lowering blood pressure and increasing blood HDL's, reducing insulin resistance, and reducing stress and anxiety. Drinking socially can also help people feel more relaxed. 

On the whole, the detrimental effects of alcohol consumption for athletes far outweigh any benefits. The main physiological systems that can be influenced by alcohol (ethanol) intake include muscular, thermoregulatory, metabolic, and neurological functions. Performance of both aerobic and anaerobic exercise can be impaired; however, the topic is still relatively unexplored with variable results. There are very few studies on the topic of alcohol and performance, and the reluctance of ethics committees to allow researchers to purposefully induce intoxication for athletic subjects is hardly surprising. 

Thermoregulatory: Alcohol is well known to inhibit the anti-diuretic hormone (ADH), which helps conserve bodily fluid volume by changing urine output, and control blood pressure. Alcohol also has a strong peripheral vasodilation effect, increasing fluid losses through skin evaporation. So this combined effect of increased urine water loss and increased sweat loss can lead to dehydration, exacerbated in athletes who are exercising and already have an increased sweat rate, or possible fluid deficit. These facts stand true for drinks with 4% alcohol or greater only, as low alcohol beers don't seem to have the same dehydrating effect during the recovery period. 

Metabolic: Alcohol not only provides a significant source of energy (29kJ per gram), which can add to long term weight management issues when consumed at high levels, but it also has effects on glucose metabolism. Firstly it is important to understand that glucose availability plays a fundamental role in endurance performance. Alcohol intake is known to cause hypoglycaemia, which is the lowering of blood glucose levels and can also reduce the uptake of glucose by the muscles which affects subsequent storage post-exercise.   

There is strong evidence to show that alcohol can affect glucose metabolism and specifically glucose storage, but there is also some research showing that this can be negated or lessened by adequate carbohydrate feedings post-exercise. Even so, the consumption of too much alcohol after exercise can easily interfere with optimum recovery strategies and carbohydrate intakes.  

Neurological:  Alcohol acts directly on the central nervous system (CNS) to slow its capabilities. There is clear dose-related impairment of reaction time, balance, memory, fine motor skill accuracy, vision and recognition with alcohol intake. Performance in most sports would certainly rely on one or more of these skills, and alcohol intake would therefore be detrimental to performance in the majority of sports, if not all of them. There is also a strong link to poor sleep after intoxication, related to greater disturbances throughout the night, and fewer periods of deep sleep. The direct cause of these neurological changes remains unclear and is probably multifactorial. 

Muscular: There is some evidence using in-vitro and rodent models, of muscle damage and reduced strength output with alcohol use, but there is very little human scientific evidence. This doesn't mean it isn't happening, there just aren't clear mechanisms shown yet. In theory, though, exercise-induced muscle damage and injury results in a natural inflammatory response that increases blood flow to the injured area. Recommended treatments include applying ice and elevating the limb to reduce blood flow, and because alcohol acts as a peripheral vasodilator it is acting against this by increasing blood flow to the area. Secondary to this is that intoxication during the injury recovery period could lead to the athlete not following appropriate recovery guidelines, only to further aggravate the injury.  

having a beer after sport a post-match beer is a staple for some sports

The Hangover

Most of what I have discussed so far is in relation to the acute intake of alcohol, however, the effects of alcohol do not disappear once the blood alcohol levels have reduced. Binge drinking can have a more lasting effect, often called a hangover...

There are a large number of physical effects that cause a hangover, and it is not well understood. Some of the causes may include dehydration, lack of sleep from staying up late and disruptions in the sleep interval, hypoglycaemia, electrolyte imbalance, gastric irritation, plus disturbances in cardiovascular function like increased heart rate and blood pressure. Research has shown that aerobic capacity can be reduced by 11% in athletes with a hangover. All of this can leave an athlete unable to train or compete as vigorously as a non-hungover athlete, certainly reducing their competitive edge. 

Injury risk

Alcohol consumption directly before training or competing is probably rare, although more commonly athletes will partake in exercise after a binge episode the night before, while potentially still being under the influence. Alcohol generally reduces one's inhibitions and consequently increases risk-taking behaviors, and it is also known to increase levels of aggression in certain people. With this in mind plus all the other physical effects of a hangover, it is believable that research has shown a causative effect on injury incidence. It has been shown that the incidence of injury rates was much higher at 54.8% in drinkers compared to 23.5% in non-drinkers.

Long term usage

Having discussed only the short term effects of alcohol intake, it is important to understand the long term effects also. Heavy and chronic alcohol intake can increase a person's risk of multiple long-term health issues. These include inflammation of the liver and fatty liver, cardiovascular disease, and some cancers. It can also compromise the body's immune system and increase susceptibility to other illnesses. 

Recommendations

There are currently no specific recommendations for alcohol consumption in athletes, except to follow moderate drinking guidelines for the general population. Avoiding binge drinking is always recommended, and is worse for health than moderate intakes. Alcohol is a potentially fatal drug and is banned in certain Olympic Sports, but education is the best method for appropriate use of this social and legal substance.

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