A study by Oxford University researchers has shown that devoted fans are in risk of heart attack due to the intense levels of physical stress whilst watching their team play.
The Oxford study tested saliva from Brazilian fans before, during and after their shocking 7-1 defeat to Germany at the 2014 World Cup.
It found that levels of the hormone cortisol rocketed during the semi-final loss.
Whilst cortisol is essential to responding to life's daily stresses, too much cortisol over time can lead to constricted blood vessels, higher blood pressure and damage an already weakened heart.
Raised cortisol can also give people a feeling of impending doom, that their life is in danger or they are under attack.
Speaking to the BBC about the findings, Dr Martha Newson, researcher at the Centre for the Study of Social Cohesion at Oxford, said:
Cortisol rocketed during live games for the fans who were highly fused to the team. It was particularly high during games where their team lost.
Interestingly, there were no differences in cortisol concentrations between men and women. Despite preconceptions that men tend to be more bonded to their football teams, women were in fact found to be slightly more bonded to their national team than the men.
Previous research has established an increase in heart attacks among fans on important match days, whether they are supporting club or country.
However, coping techniques such as humour and hugging were used to reduce stress to pre-match levels by the final whistle.