Results of a study conducted at the University of Southern California (USC) has shown that adolescent rats that freely consumed large quantities of liquid solutions containing sugar or high-fructose corn syrup (HFCS) in concentrations comparable to popular sugar-sweetened beverages experienced memory problems and brain inflammation, and became pre-diabetic. Scott Kanoski, an assistant professor at USC’s Dornsife College of Letters, Arts and Sciences, and colleagues investigated the effects of sugar and HFCS on 76 rats. Adolescent or adult male rats were given 30-day access to chow, water, and either (1) 11% sucrose solution, (2) 11% HFCS solution, or (3) an extra bottle of water (control). Approximately 35-40% of the rats’ daily calories were obtained from sugar or HFCS. The rats then underwent a series of tests. Results showed that in adolescent rats, HFCS intake impaired hippocampal-dependent spatial learning and memory in a Barne’s maze, whilst moderate learning impairment was also observed in the rats in the sucrose group. Further investigation revealed that protein expression of the pro-inflammatory cytokines interleukin 6 and interleukin 1β was increased in the hippocampus of the adolescent rats fed HFCS, while liver interleukin 1β and plasma insulin levels were elevated in both adolescent-exposed sugar groups. On the other hand, intake of HFCS or sucrose in adults did not impact spatial learning, glucose tolerance, or neuroinflammatory markers. “The brain is especially vulnerable to dietary influences during critical periods of development, like adolescence,” said Kanoski, “Consuming a diet high in added sugars not only can lead to weight gain and metabolic disturbances, but can also negatively impact our neural functioning and cognitive ability.”
Hsu TM, Konanur VR, Taing L, Usui R, Kayser BD, Goran MI, Kanoski SE. Effects of sucrose and high fructose corn syrup consumption on spatial memory function and hippocampal neuroinflammation in adolescent rats. Hippocampus. 2014, Sep 20.[Epub ahead of print].