Alcohol intake in youth has been associated with aggressive behavior and violence, but the influence of sugary and carbonated soft drinks on behavior in youth has not been well studied. There may be a connection between high sugar intake and violent behavior reflecting abnormally low sugar levels as a precipitant of high sugar intake.This cross-sectional survey by Hemenway and colleagues of Boston youth conducted at public high schools determines the association between self-reported intake of nondiet carbonated soft drinks and aggressive behaviors.
Study Synopsis and Perspective
Public health researchers and nutrition advocates have criticized consumption of carbonated soft drinks because they may fill people up with empty calories, sugar, and caffeine, but new research published online October 24 in Injury Prevention suggests that the drinks also may be linked with, or may be a strong marker for, violent behavior in teenagers.“This is the first study to suggest such an association,” said David Hemenway, MD, professor of public health and director of the Injury Control Center at the Harvard School of Public Health, Boston, Massachusetts, and the study’s lead author, in an interview with Medscape Medical News.After controlling for sex, age, race, body mass index, typical sleep patterns, tobacco use, alcohol use, and having family dinners, the investigators found that high consumption of carbonated, nondiet soft drinks was associated with a statistically significant 9% to 15% greater likelihood of engaging in aggressive behaviors. Heavy soft drink use had about the same effect as tobacco and alcohol on violence.“This is just one study, and it needs to be looked at in more detail.” Dr. Hemenway said. He was reluctant to call it a cause-and-effect relationship, stressing that the exact sugar or caffeine content in the soft drinks was “unknown,” and that “possibly other factors not accounted for in our analysis are related to high soft drink consumption and aggression.”Dr. Hemenway and coauthors found that teenagers who drank more than five 12-ounce cans of carbonated soft drinks each week were more likely to carry a weapon and commit violence against friends, dates, and siblings. The study also found that the relationship appears to be a dose-response relationship, with the strongest relationships shown for teenagers drinking 14 or more cans per week. Of those adolescents, 42.7% carried a gun or knife, 58.6% were violent toward their peers, 26.9% were violent toward dates, and 45.3% perpetrated violence toward other children in their family. These percentages were significantly higher than in each of the 3 other consumption categories (≤1 can, 2 – 4 cans, and 5 – 7 cans in the last 7 days), and there was a statistically significant, linear increase in consumption linked to each of the 4 violence behaviors (P ≤ .001). Nearly 1 in 3 students were drinking at least 5 cans of carbonated soft drinks. The study used self-report data from the Boston Youth Survey, a biennial, paper-and-pencil survey of ninth- to twelfth-grade students in Boston public schools to evaluate the effect of soft drink use on aggressive and violent behavior.The 2725 high school students selected for the study were not representative of adolescents across the United States: 50% were black or multiracial, 33% were Hispanic, 9% were white, and 8% were Asian. Of these groups, only Asians were found to drink much less than the others.The study was not able to show a relationship between soft drink consumption and obesity, which has been shown in other studies. Heavy soft drink use was also associated with other dimensions; for example, getting insufficient sleep and using alcohol and tobacco within the past 30 days.Dr. Hemenway acknowledged several study limitations, including the self-report of the data, the generalizability to other adolescents, and the lack of information on the sodas themselves. In the discussion section, the authors write that a “direct-cause-and effect relationship between soft drink consumption and aggression is one possibility,” adding that “various ingredients, including carbonated water, high fructose corn syrup, aspartame, sodium benzoate, phosphoric or citric acid, and often caffeine…might affect behaviour.”The author introduces his study by reminding readers of the “Twinkie defense,” which was used successfully to reduce Dan White’s conviction from homicide to manslaughter for the 1978 killing of San Francisco City District Supervisor Harvey Milk and Mayor George Moscone.“I am totally not convinced,” noted Marion Nestle, PhD, MPH, Pauline Goddard professor of nutrition, food policies, and public health at New York University School of Medicine, New York City, in an email to Medscape Medical News.” As I said, I’m no fan of sodas, but [it] defies common sense.”Dr. Nestle also was not impressed with the study design. She noted: “This looks like a ‘tracking’ study to me. I don’t see how the study can conclude anything specific about soft drinks except guilt by association.” She added that “poor kids drink more soft drinks than rich kids, and they are marketed to more aggressively.“If it turns out that alcohol and junk food diets can be linked to negative behaviours,” she said, “[s]oda companies will reap what they sowed when they focused so much marketing on low-income, minority communities.”The study was supported by the US Centers for Disease Control and Prevention. It was externally peer reviewed. The authors and Dr. Nestle have disclosed no relevant financial relationships.