In a study conducted at the University of Southern
California, high fructose corn syrup-55 (HFCS-55) and sucrose, the most commonly
added sweeteners in the United States, were given to adolescent and adult male
rats to determine their impact on hippocampal-dependent spatial memory, metabolism,
and neuronal outcomes. Each rat was given either normal water (control), water
with sucrose, or water with HFCS-55 for 30 days along with normal water and
low-fat chow. After the 30 day sugar diet the rats were placed in a series of
mazes to test spatial memory, anxiety effects based on the high sugar diet, and non-hippocampus learning and memory processes.
Adolescent rats that were given the sugar sweetened beverages showed impaired
spatial memory but no effects were found on anxiety or learning and memory
processes in other parts of the brain when compared to the controls. Adult rats
on the other hand showed no difference between control and experimental groups
after placed in the 3 mazes. Plasma insulin levels, liver cytokines, and
hippocampal cytokines were also checked using a glucose tolerance test,
immunoblotting, and an enzyme-linked immunosorbent assay. As expected higher
plasma insulin levels were found in adolescent rats given the sugar sweetened
beverages, however, no such changes were discovered in adult rats. Liver
cytokines were also higher in adolescent rats on the sugar sweetened beverage
diet but, again, no such changes in adult rats were found. Only the HFCS-55 adolescent
rats had higher levels of hippocampus cytokine levels while the sucrose
adolescent rats and the adult rats showed no difference when compared to the
control groups.
This study shows that consuming excess sugar during vital development
stages can have adverse effects on cognitive development and metabolic
functions but more studies are needed to determine the effect on human
adolescents. Until then, soda and other sugar sweetened beverages should be
minimally consumed by all age groups but most specifically by adolescents.
Charlie, the results from this study are very interesting. I guess I would have thought that if sugar had any affect that it would alter both adult and adolescent memory. It is interesting that it only affects spatial memory in the developing adolescent mice. I know that in addition to what you mention about the hippocampus controlling spatial memory, it is also in charge of other forms of memory, like episodic memory. It would be interesting to see the effects on episodic memory of sucrose and high fructose corn syrup. I think it would also be interesting to see how artificial sweeteners affect hippocampal development and if these effects are more or less severe than the sucrose and high fructose corn syrup. Either way, it seems like a diet high in sugar is very more important to avoid during adolescence.
ReplyDeleteInteresting! I wonder if the affect of sugar on adolescent memory has anything to do with the microbial changes that occur in the gut around puberty that have been shown to affect neurogenesis and immune responses to inflammation. The involvement of cytokines certainly seems to suggest some correlation with an inflammatory response...
ReplyDelete
ReplyDeleteHi Charlie,
This is sort of terrifying, when you combine it with what we learned in Seminar! That study showed that artificial sweeteners, which were designed to combat diabetes and obesity, actually induced diabetes and obesity! So if we cannot use artificial sweeteners, and now we know that sucrose and high-fructose corn syrup have negative cognitive effects, what should we use?
Also, like Sarah, I wonder if the way in which sugars effects impairs cognition begins with changes in the gut microbiota (similar how to the artificial sweeteners operate).
Source: Artificial sweeteners induce glucose tolerance by altering the gut microbiota, Suez et al (you can access this from the Seminar 2 World Class site).