Football is perceived as being relatively free of the drug problems which have blighted some other sports.
Real Story is broadcast on Monday 19 May on BBC One at 1930 BST
But as the BBC's Real Story documentary discovered, the game is perhaps not as clean as previously thought.
With performance-enhancing and recreational drug abuse far more widespread than feared, BBC Sport looks at what footballers could be putting in their bodies.
Football and alcohol have a turbulent history
For many reasons, this is the drug most commonly associated with football.
Many high-profile players have suffered alcoholism, and foreign coaches have admitted to being surprised at the booze culture in English football.
The alcohol problem is, of course, nothing to do with performance enhancement.
Alcoholic drinks can reduce tension and increase aggression - but they impair judgement, co-ordination and reaction times to a great degree and can lead to dehydration.
A footballer who takes alcohol will not be doing so for sporting reasons.
Cocaine / ecstasy / speed
(also ephedrine, pseudoephedrine, phenylephrine, phenylpropanolamine)
Ecstasy and cocaine are both illegal and banned
Cocaine, ecstasy and speed are stimulants and will increase alertness, decrease tiredness and increase competitiveness.
But they also impair judgement which can increase risk of injury and if a player under the influence was involved in intense exercise, an average dose could prove fatal.
All three, it should also be noted, are illegal - and are often used as recreational drugs .
The other substances are not, but are still stimulants and could be taken inadvertently if a footballer had not done his homework.
Ephedrine, pseudoephedrine, phenylephrine and phenylpropanolamine are present in many over-the-counter cold and 'flu remedies.
Cups of tea contain caffeine which is banned in large doses
Cups of tea are a common sight at any football ground, whether being drunk by players or flung against the walls by irate managers.
Yet tea, coffee, chocolate, painkillers and many energy drinks contain caffeine which works as a stimulant and - in large quantities - is banned.
Some athletes have taken large doses to improve alertness and reaction times and footballers need to be aware of the dangers of over-dosing on the substance.
To put in context, you would probably have to drink nine cans of cola in a short time to inadvertently produce a high reading - but as everybody's metabolism is different, all footballers have to be wary.
Salbutamol / Salmeterol / Terbutaline
Asthma treatments need clearance as they contain banned substances
These substances work by relaxing muscles in the airwaves, and when inhaled they can be used to treat asthma.
If prescribed by a respiratory specialist, they will be permitted, but they have side effects which could be beneficial for those seeking to gain an unfair advantage in sport.
Although normally inhaled, it is believed when injected they can help develop muscle mass and reduce body fat - an obvious bonus for any footballer looking to boost endurance and strength.
But there are potentially serious side-effects, such as nausea, headaches, dizziness, fever, muscle cramps and rapid heart rates and palpitations.
Marijuana will not enhance performance, but it is still banned
Cannabinoids are hallucinogenic drugs which are most likely to be taken as a recreational drug in the form of marijuana.
Their effects are well-documented, and include feelings of relaxation, reduced inhibitions and a loss in perception of time and space.
Although the relaxation could help ease nerves before a big match, these drugs would have a massively detrimental on performance.
Nevertheless, any player found taking marijuana would face an FA rap - not to mention police action as it is a Class C illegal substance.
Thanks to Sam Howells (MSc. BSc), Senior Sports Physiologist, Lilleshall Sports Injury and Human Performance Centre