New research gives more reasons for you to advise teenagers to avoid junk food and energy drinks, and even better reasons to encourage them to exercise.

The latest evidence on how the teenage brain is particularly vulnerable to environmental influences, both good and bad, as it matures into adulthood is marshaled into review articles featured in a special issue of the journal Birth Defects Research entitled “The dynamic and vulnerable teenage brain” issued by the Teratology Society.

Junk food – soda, potato chips, and the like – is one of the bad influences, and not just on the waistline, according to a review by Amy Reichelt, PhD, and Michelle M. Rank, PhD, of the Royal Melbourne Institute of Technology University in Melbourne (Birth Defects Res. 2017 Dec 1. doi: 10.1002/bdr2.1173).

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High fat, high sugar diets already have been linked to poorer cognitive function and executive performance in adolescents. Lately, it’s become clear that junk food diets also trigger “functional changes in dopaminergic signaling, which in turn may modulate” the developing gamma-aminobutyric acid (GABA) system, the researchers said. GABA is thought to be a principal inhibitory neurotransmitter in the prefrontal cortex, and glutamate the principal excitatory neurotransmitter. The balance between the two is critical for high order cognition and behavior.

Under construction

“Because key neurotransmitter systems in the brain responsible for inhibition and reward signaling are still developing during the teen years, existing primarily on junk food could negatively affect decision making, increase reward-seeking behavior and influence poor eating habits throughout adulthood,” Dr. Reichelt said in a press release about the special issue.

The good news is that “the heightened neuroplasticity during adolescence ... offers a window in which diet-induced cognitive decline may be particularly amenable to intervention. This provides opportunities for nutritional intervention strategies in high-risk individuals,” she and Dr. Rank concluded in the review.

Although the literature is thinner than with junk food, there are similar concerns about the effects of energy drinks and their high levels of caffeine and taurine. Energy drinks likely are detrimental to the brain function of children and adolescents, especially when mixed with alcohol, according a second review by Christine Perdan Curran, PhD, and Cécile A. Marczinski, PhD, of Northern Kentucky University, Highland Heights. (Birth Defects Res. 2017 Dec 1. doi: 10.1002/bdr2.1177).

“We don’t know enough about the effects of high consumption of energy drinks and the ingredients found in them at this critical time in mammalian brain development,” but “our recent findings in adolescent and young adult mice exposed to high taurine levels indicate there can be adverse effects on learning and memory and increased alcohol consumption in females,” Dr. Curran said in the press release.

In short, energy drinks in adolescence raise “serious concerns about adverse effects on the brain,” the researchers concluded in their review.

It’s a happier story with exercise, according to two more reviews in the teenage brain issue.

Less couch time

“It is clear that helping adolescents dedicate more of their time to exercise, especially high intensity or aerobic activities, may not only better their physical health but also positively influence the way their brain is structured and how it functions,” said Megan Herting, PhD, and Xiaofang Chu of the University of Southern California, Los Angeles (Birth Defects Res. 2017 Dec 1. doi: 10.1002/bdr2.1178).

Aerobic exercise in the teenage years seems to improve attention, planning, problem solving, working memory, and inhibitory control. MRI studies, meanwhile, suggest that higher aerobic fitness correlates with beneficial cortical, subcortical, and white matter structural connectivity profiles in older adolescents. In a functional MRI study of 15- to 18-year-old boys, Dr. Herting and B.J. Nagel, PhD, found that the hippocampus of 17 less fit adolescents was significantly more active than that their 17 fitter peers during a word recall test, suggesting “that exercise may influence how the brain encodes new memories and that lower-fit teens may need to utilize additional brain resources to learn something new” (J Cogn Neurosci. 2013 Apr;25[4]:595-612).

Boosting the benefit

Exercise also helps with substance abuse, an effect that “appears to be attributable to more than just time occupied by the activities,” according to a review led by Nora L. Nock, PhD, of Case Western Reserve University, Cleveland (Birth Defects Res. 2017 Dec 1. doi: 10.1002/bdr2.1182).

“Substance use in adolescence has been associated with adverse structural and functional brain changes, and may further exacerbate the natural imbalance” between inhibitory and excitatory neurotransmitters, “leading to further heightened impulsive and reward-driven behaviors,” the authors said.

Exercise offsets the effects by inducing structural and functional changes in the brain, including neurogenesis and angiogenesis. “If integrated during adolescence, a window of heightened reward sensitivity and neural plasticity, exercise may help to reinforce ‘naïve’ or underdeveloped connections between neurological reward and regulatory processes ... and, in turn, help offset or dampen reward seeking from substances while concomitantly improving cardiovascular health as well as academic and social achievement,” Dr. Nock and her colleagues said.

The team is studying “assisted exercise,” which helps people peddle about 35% faster on a stationary bike than they would be able to on their own. “It may be able to provide even greater effects in suppressing reward from substance use due to potentially larger increases in neurotransmitters (e.g., dopamine) and neurotrophic factors (e.g., BDNF [brain-derived neurotrophic factor]), which may be particularly beneficial in adolescents with SUD (substance use disorder) having a dopamine deficit due to genetic variation and/or lower levels of striatal dopamine receptors ... during substance abstinence,” they said.

Given those and other findings, Dr. Nock and her colleagues proposed that exercise “be initiated during early abstinence and, potentially, started before integrating other cognitive behavioral treatment components” in adolescents with SUDs.

The authors did not report any industry disclosures.

aotto@frontlinemedcom.com

Junk food, energy drinks may damage teen brains