A Surprising Effect of Soda Drinking

In this Harvard Magazine article, Elizabeth Gudrais reports on a study of 1,878 Boston public high-school students that found heavy consumers of non-diet soda (five or more cans a week) were significantly more violent than peers who drank less soda. Specifically, those who drank more soda were more likely:

• To have behaved violently toward peers (57 percent versus 39 percent of those who drank less soda);
• To have behaved violently toward another child in their own families (42 percent versus 27 percent); 
• To have behaved violently in a dating relationship (26 percent versus 16 percent); 
• To have carried a gun or a knife during the previous year (40 percent versus 27 percent). 

These correlations to violent behavior were as strong as those of alcohol and tobacco use, in some cases stronger, and they surprised researchers. “When you think about the causes of violence,” said the study’s lead author, David Hemenway of the Harvard School of Public Health, “soft drinks are not on the map of variables that you tend to look at.” 

The findings of the Boston study have since been replicated in a survey of 5,000 California adolescents, 16,000 students in public, private, and parochial schools across the U.S., and 3,000 low-SES American five-year-olds (the question about guns and knives was dropped for this group). Hemenway plans to study school disciplinary and police records to see if the correlation holds up with more objective data. 

What’s behind this link between soda and violence? Is there a third variable, perhaps the quality of parenting, that influences soda consumption and aggressive behavior? The researchers controlled for parenting and still found a strong correlation. Do excess caffeine and sugar produce a blood-sugar crash that leaves soda drinkers irritable and prone to violence? Or does drinking soda deprive youth of nutrients from healthier fare that might promote calmer behavior? More research is needed.

“Soda and Violence” by Elizabeth Gudrais in Harvard Magazine, November/December 2012 (p. 9-10), http://harvardmagazine.com/2012/11/soda-and-violence 

From the Marshall Memo #460