Teenagers are significantly more likely to be aggressive and violent if they regularly consume fizzy soft drinks, a study has found.
Consumption of more than five cans of non-diet carbonated drinks a week was associated with behaviour that included carrying weapons and violent assaults.
The US researchers do not yet know if the link is causal, but have not ruled this out. It may be that unknown factors causing aggression in youngsters also influence their dietary habits.
The findings, reported online in the journal Injury Prevention, are based on a survey of 1,878 teenagers aged 14 to 18 from 22 state schools in Boston.
Participants were asked how many non-diet fizzy soft drinks they had consumed over the past week.
Intake level was measured in cans. Up to four cans was considered “low”, and five or more “high”. Just under one in three pupils fell into the “high” category, some drinking more than two or three cans a day.
The scientists then looked for potential links to violent behaviour.
Youngsters were asked if they had been violent towards their peers, a brother or sister, or a partner, and whether they had carried a gun or knife in the past year.
Overall, frequent soft drink consumption was associated with a 9 per cent to 15 per cent increased likelihood of engaging in aggressive behaviour.
Violence and weapon-carrying was in any event common among the teenagers, who largely represented ethnic minorities from poor backgrounds. Of the group, 50 per cent were black or multi-racial, 33 per cent Hispanic, 9 per cent white and 8 per cent Asian.
However, rates of violent behaviour increased in a “dose response” as students consumed more fizzy drinks, the researchers found.
Just over 23 per cent of teenagers drinking one or no cans a week had carried a gun or knife, rising to just under 43 per cent of those drinking 14 or more cans.
For the same increase in fizzy drink consumption, the proportion of those who had shown violence to a dating partner rose from 15 per cent to 27 per cent.
Rates of violence towards peers rose from 35 per cent to more than 58 per cent, and towards siblings from 25.4 per cent to more than 43 per cent.
“There was a significant and strong association between soft drinks and violence,” say the researchers, led by Dr Sara Solnick from the University of Vermont.
“There may be a direct cause-and-effect relationship, perhaps due to the sugar or caffeine content of soft drinks, or there may be other factors, unaccounted for in our analyses, that cause both high soft drink consumption and aggression.”
A previous crime study recommended using tax and pricing policies to persuade young people to consume soft drinks instead of alcohol, the researchers noted.
“Our findings suggest that policies to encourage soft drink consumption may be a mistake.”