Intake of Soft Drinks Linked with

Violent Behaviour in Children

Laura Newman | Unknown

Clinical Context

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 non-diet 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.

Study Highlights

  • The Boston Youth Survey is a biennial paper-and-pencil survey of 9th to 12th graders in Boston public schools.
  • Excluded were religious, private, and other schools outside of the public school system and schools that serve severely disabled children.
  • In 2008, a total of 22 of 31 eligible schools participated.
  • The survey was administered during a 40-minute classroom period by trained youth workers and others.
  • Within each grade in each school, classrooms were randomly selected for survey administration.
  • 1 classroom was selected per grade per school (approximately 100 to 110 students).
  • Of 2725 students selected for participation, 69% completed the survey.
  • Regular (nondiet) carbonated drink consumption was assessed with a question asking about intake in the past 7 days.
  • Soda intake was measured in cans (1 can for a 12-oz serving), and a 20-oz bottle was reported as 2 cans.
  • Participants were analyzed in 2 categories: those who consumed up to 4 cans in the past 7 days and those who consumed 5 or more cans in the past 7 days (classified as heavy consumers).
  • Self-reported aggressive and violent behavior was assessed in 3 ways: violence toward other adolescents, violence toward other children in the family, and violence toward someone in a dating relationship.
  • The respondents were also asked if they had carried a gun or knife in the past year.
  • Other variables controlled for were age, ethnicity, sex, body mass index, alcohol consumption, smoking tobacco, having dinner with families, and getting less than 6 hours of sleep on any night.
  • There were 53% women, mean body mass index was 24 kg/m2, half were black, 33% were Hispanic, 9% were white, and 8% were Asian.
  • Asians were the only group to be less likely to drink fewer than 5 cans of soda in the past 7 days.
  • More than one third did not have dinner with their families in the past week.
  • Across the sample, 29.8% of youth reported drinking more than 5 cans of soft drinks per week.
  • Those who consumed more soft drinks also were more likely to smoke and to consume alcohol at least once in the past 30 days.
  • Frequent consumers of soft drinks were more likely to have carried a gun or knife within the past year compared with those who were not frequent consumers.
  • They were more likely to have been violent with a sibling, with another adolescent, or with someone in a dating relationship.
  • This association remained consistent after controlling for body mass index, eating dinner with the family, and other variables.
  • Heavy soft drink consumers were not more likely to have less than 6 hours of sleep.
  • When intake of soft drinks was divided into 4 categories, there was a dose-response pattern, with higher consumption having stronger associations.
  • High intake of soft drinks resulted in a 5% to 9% increase in the probability of engaging in aggressive behaviors, and the magnitude of the impact was similar to that seen with use of tobacco or alcohol.
  • The influence of soft drink consumption on carrying a weapon was not as strong as that of alcohol or tobacco use.
  • The authors concluded that consumption of nondiet soft drinks was associated with more self-reported aggressive behaviors in youth, that such intake may be a marker of aggressive behavior, and that a strategy of encouraging soft drink intake may be misguided.

Clinical Implications

  • Higher intake of nondiet carbonated soft drinks in youth is associated with increased aggressive behaviors.
  • The association of soft drink intake with aggressive behaviors in youth is dose dependent. The influence of soft drink consumption on carrying a weapon was not as strong as that seen with alcohol or tobacco use. Children who had a high intake of soft drinks were more likely to have been violent toward a sibling, another adolescent, or someone in a dating relationship.