New rat research reveals potentially lasting effects of adolescent sugar overconsumption on adult reward sensitivity
A recent animal study suggests that consuming high amounts of sugary foods during adolescence can produce long-lasting changes in the brain’s reward system and reduce the enjoyment of sweet tastes in adulthood. Researchers report that rats given excessive sucrose during their adolescent period later displayed diminished behavioral and neural responses to sweet rewards. The diminished response was linked to lower activity in the nucleus accumbens, a central region of the brain’s reward circuitry. These findings shed light on how early-life diets rich in sugar might influence vulnerability to reward-related disorders in later life.
Source: Dawn Peters – Wiley
Image Source: NIDA (public domain)
Original Research: “Long-lasting deficits in hedonic and nucleus accumbens reactivity to sweet rewards by sugar overconsumption during adolescence” by Fabien Naneix, Florence Darlot, Etienne Coutureau and Martine Cador, European Journal of Neuroscience. Published online January 13, 2016. DOI: 10.1111/ejn.13149
Abstract (summary)
This study examined how continuous access to a sweet solution during the adolescent period affects later responses to sweet rewards. Adolescent rats were given continuous access to a 5% sucrose solution from postnatal day 30 to 46, a window corresponding to adolescence in rodents. During this exposure period the animals escalated their sucrose intake. When tested in adulthood (postnatal day 70), sucrose-exposed rats consumed less sucrose in two-bottle choice tests than rats that had not been exposed, indicating a reduced sensitivity to the rewarding properties of sucrose.
Detailed behavioral testing showed that sucrose-exposed animals exhibited fewer hedonic orofacial reactions to intraoral infusions of sweet solutions, while their responses to neutral (water) or aversive (quinine) tastes were unchanged. Neural analysis revealed that this persistent hedonic deficit was accompanied by lower c-Fos expression in the nucleus accumbens, a region critically involved in processing pleasure and reward. Together, these results indicate that high sucrose intake during the sensitive developmental period of adolescence can produce prolonged reductions in both the behavioral enjoyment of sweet tastes and the responsivity of a central reward structure.
Dr. Martine Cador, the study’s senior author, highlighted the relevance of these findings given the marked increase in consumption of sweet, palatable foods during adolescence in many modern societies. The research supports the idea that chronic overstimulation of the reward system in adolescence may alter its later functioning, potentially increasing susceptibility to disorders that involve aberrant reward processing, such as certain forms of substance abuse or disordered eating.
Key methodological details reported by the authors include:
- Adolescent exposure: continuous access to 5% sucrose solution from postnatal day 30 to 46.
- Adult testing: assessments performed at postnatal day 70, including two-bottle choice tests and intraoral taste infusions to measure hedonic orofacial reactions.
- Neural measures: evaluation of c-Fos, an indicator of neural activation, in the nucleus accumbens to assess reward-related brain activity.
Implications: The study emphasizes that dietary patterns during adolescence can have durable consequences for how the brain processes rewarding stimuli later in life. Reduced hedonic sensitivity and blunted nucleus accumbens reactivity may alter motivation and pleasure responses, with potential implications for behavior and mental health. While this research was conducted in rats, the findings raise important questions about how excessive sugar consumption during human adolescence might influence adult reward processing and risk for related disorders.
For readers interested in the original scientific report, the published paper provides the full experimental details, statistical analyses, and discussion of limitations and future directions. The authors conclude that a history of high sucrose intake during adolescence produces long-lasting deficits in hedonic processing that could contribute to reward-related disorders.