Why does soft drink consumption in children and adolescents seem to elicit aggression and deficits in attention? Is sugar driving these responses? Is it the caffeine … or something else perhaps? More importantly, would restricting soft drinks from your child sufficiently reduce these symptoms?
Suglia et al (1) reported a strong association between soft drink consumption and behavior problems in 5-year-olds. When sociodemographic factors were adjusted for, soda consumption was linked to aggressive behavior in a dose-dependent manner. Further, a statistically significant trend for soda consumption and attention problems was also noted. Similarly, another study (2) published in the BMJ’s Injury Prevention journal involving teenagers this time found the same association: Those consuming more soft drinks were much more likely to reveal violent behavior. While no cause could be established in either study, several possibilities were offered including caffeine, sugar, and underlying organic conditions.
Both these recent studies rapidly entered circulation, widely disseminating throughout academic circles and even in the media, spurring much debate about how soft drink consumption contributes to these negative findings. While the associations are solid, the causation is not. If causation is not recognized, then we cannot be sure how to fully eliminate the problem if it lies beyond soft drinks alone. There is good reason to suspect the cause related to soft drinks is also a factor that exists independently from these sweetened beverages.
There are two likely causes within the carbonated drinks that affected their behavior: sugar and caffeine. When Suglia et al investigated sugar as a culprit, sugar through fruit juice consumption was associated with lower aggression scores rather than higher ones. Moreover, other controlled studies have failed to find negative behavioral changes in children following large consumption of sugar (3) (4). This does not absolve sugar from the numerous other negative effects it has on children and adults alike, but aggression is unlikely to be sugar-driven.
The other possible trigger – caffeine – is a stimulant, but evidence of aggressive behavior subsequent to caffeine use, at least directly, is lacking. Contrary to what would be expected, regular coffee compared to decaffeinated coffee produced fewer aggressive responses (5), and in another study where caffeine was compared to a placebo, subjects only demonstrated aggression when under the impression that they ingested an arousing drug (6).
What we do know, however, is that caffeine can provoke sleep dysfunction as a delayed effect in sensitive individuals and especially children. Sleep dysfunction as a result of caffeine consumption in children should be proposed as the most likely explanation, rather than a direct cause-and-effect relationship between any particular ingredient in the sodas and poor behavior. In this case, correlation does not signify direct causation, but rather indirect causation. Higher caffeine consumption has been inextricably linked with sleep dysfunction in the form of shorter duration of sleep and increased wake time after sleep onset (7) (8). Sleep deprivation in school-age children greatly correlates with aggressive behavior and problems in attention (9) (10), which is precisely what Suglia et al observed. This problem can become chronic as sleep deprivation influences hormones that lead to cravings to more sugary foods and beverages, which could very likely have added caffeine, beginning a vicious cycle. To make matters worse, chronic sleep deprivation in growing individuals can lead to permanent deficits in brain growth and synaptic function in adulthood (11).
Due to the lack of clarity concerning causality in these studies, news articles are incorrectly emphasizing the sugary component of sodas as the determinant of these negative behaviors despite a lack of association in normal children. Even if it is noted that this causality is uncertain, concerned parents will simply take care to limit sugar intake, or worse … only soft drinks will be eliminated and possibly substituted for other caffeinated beverages or different types of sweets. Reducing sugar consumption in children and adolescents is highly beneficial for others reasons, such as maintaining insulin sensitivity (13) and promoting healthy brain development by preventing changes in brain structure and decrements in cognitive function from excess sugar (12), but it will not resolve behavioral problems stemming from sleep dysfunction. If there are other sources of caffeine in the diet and/or sleep deprivation persists for other reasons, the problem may improve modestly by limiting soft drinks, however it certainly would not vanish. If, on the other hand, caffeine is identified as an indirect casual factor that leads to adverse behaviors through degradation in sleep quality, healthcare professionals and parents can more successfully control the outcome of a child’s behavior by instead restricting all forms of caffeine and in addition, ensuring healthy sleep habits by adjusting other variables such as environmental stress, number of extracurricular activities and chores, distracting technology, and/or whatever else is preventing the child or teenager from getting the recommended amount of sleep.
1. Shakira F. Suglia, Sara Solnick, and David Hemenway. Soft Drinks Consumption Is Associated with Behavior Problems in 5-Year-Olds. The Journal of Pediatrics, 2013 DOI: 10.1016/j.jpeds.2013.06.023
2. Sara J Solnick, David Hemenway. The ‘Twinkie Defense’: the relationship between carbonated non-diet soft drinks and violence perpetration among Boston high school students. Inj Prev, 2011 DOI: 10.1136/injuryprev-2011-040117
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