High-sugar diet in adolescence can impair memory later

While previous research linked high-sugar diets with obesity and heart disease and even impaired memory function, less is known about its effects on mental development particularly on the hippocampus -- brain region critical for learning and memory.

The new findings, published in the journal Translational Psychiatry, showed that higher consumption sugar during early life increased the level of parabacteroides -- a type of gut bacteria. The higher the level of parabacteroides, the worse the animals performed in the memory and learning task.

For the study, the team gave juvenile rats their normal chow and an 11 percent sugar solution, which is comparable to commercially available sugar-sweetened beverages.

The rats were then subjected to a hippocampus-dependent memory task designed to measure episodic contextual memory, or remembering the context where they had seen a familiar object before.

"We found that rats that consumed sugar in early life had an impaired capacity to discriminate that an object was novel to a specific context, a task the rats that were not given sugar were able to do," said lead author Emily Noble, Assistant Professor at the University of Georgia in Athens, US.A"Early life sugar consumption seems to selectively impair their hippocampal learning and memory," Noble said.

Additionally, the researchers experimentally increased levels of parabacteroides in the microbiome of rats that had never consumed sugar. Those animals showed impairments in both hippocampal dependent and hippocampal-independent memory tasks.

"(The bacteria) induced some cognitive deficits on its own. We found that the bacteria alone was sufficient to impair memory in the same way as sugar, but it also impaired other types of memory functions as well," Noble said.

She noted that future research is needed to better identify how the gut bacteria alters development of the brain.