Junk Food = Junk Mood
Teen consumption of “junk foods” and other unhealthy dietary choices may be contributing significantly to the burgeoning mental health crisis in that age group.
Significant increases in the prevalence of adolescent emotional distress and behavioral problems have occurred over the past several generations.1 Paralleling this mental health pathology among young people is a reduction in the quality of adolescents’ diets over recent generations with decreasing consumption of raw fruits, high-nutrient vegetables and associated increases in fast food, snacks and sweetened beverages2 with resulting obesity3.
While data are still relatively scarce from randomized, controlled trials to demonstrate the efficacy of healthful eating on psychiatric disorders, there is considerable epidemiologic evidence. Most of that literature is based on studies of adults; however very recently there is emerging evidence to suggest similar correlations with adolescent diets.
Cross sectional studies on the effect of diet quality on adolescents indicate an association between dietary patterns and mental health in adolescence. Poorer emotional states and behavior were seen in adolescents with a typical Western dietary pattern high in red and processed meats, takeaway foods, confectionary and refined foods compared to those who consumed more fresh fruit and vegetables4,5.
The first prospective cohort study on the effect of diet quality on mental health of adolescents was published in 2011, based on over 3000 adolescents ages 11- 18 years old6. Participants with poor diet quality at baseline had more emotional and behavioral problems; these worsened with time passage if a poor diet continued but improved if their diets improved. Those with good baseline diet quality had fewer psychiatric problems but if that diet deteriorated, so did their mental health. A healthy diet was defined as one that included fruit and vegetables as “core food groups” and included both two or more servings of fruit per day and four or more servings of vegetables, as well as general avoidance of junk food such as processed foods including chips, fried foods, chocolate, sweets, and ice cream.
In October 2013, results from a very large prospective cohort study of 20,000 women and their young children indicated early poor nutritional exposures in utero were related to risk for behavioral and emotional problems in their children7. These difficulties were more severe if the child’s dietary pattern after birth was also poor.
The mechanisms behind these effects in children and adolescents are not well described. Beyond the obvious neurologic development in utero, we know that neurologic development continues after birth and extends throughout childhood and adolescence into young adulthood8. It therefore appears logical that a highly nutrient dense diet could result in an advantage in brain development with cognitive, emotional, and behavioral implications.
This could be an effect additional to the now apparent influence diet has on the mental health of adults through inflammation and the immune system, oxidative stress and neurotrophic factors. Focus on psychiatric disorders in childhood and adolescence is particularly important given the fact that three quarters of lifetime psychiatric disorders will first emerge by late adolescence or early adulthood9. There appear to be a multitude of reasons why judicious choice of dietary patterns are particularly important to establish early.
1 Twenge JM, Gentile B, DeWall CN, Lacefield K, et al. (2010) Birth cohort increases in psychopathology among young Americans, 1938–2007: A cross-temporal meta-analysis of the MMPI.Clin Psychol Rev 30: 145–154. 21. 2 Cavadini C, Siega-Riz AM, Popkin BM (2000) US adolescent food intake trends from 1965 to 1996. West J Med 173: 378–383. 3 Ogden CL, Flegal KM, Carroll MD, Johnson CL (2002) Prevalence and trends in overweight among US children and adolescents, 1999–2000. Jama 288: 1728–1732. 4 Oddy WH, Robinson M, Ambrosini GL, de Klerk NH, et al. (2009) The association between dietary patterns and mental health in early adolescence. Prev Med 49: 39–44. 5 Jacka FN, Kremer PJ, Leslie E, Berk M, Patton G, et al. (2010) Associations between diet quality and depressed mood in adolescents: results from the Healthy Neighbourhoods study. Aust N Z J Psychiatry 44: 435–442. 10. 6 Jacka FN, Kremer PJ, Berk M, de Silva-Sanigorski AM, Moodie M, et al. (2011) A prospective study of diet quality and mental health in adolescents. PLoS ONE 6(9)