Rodents in the study were given their normal food in addition to an 11% sugar solution. The liquid is comparable to sugar-sweetened beverages available in stores.
Afterward, researchers had the rats carry out a memory task that depended on the hippocampus, the region of the brain that’s critical to learning and memory.
It was meant to evaluate how well the rodents remembered the context where they had previously seen a familiar object.
“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,” Noble said.
A second memory task evaluated basic recognition memory, a function that the hippocampus is not involved in. This task looked into how rats could identify something they’d seen before. Sugar did not affect their recognition memory in this task.
“Early life sugar consumption seems to selectively impair their hippocampal learning and memory,” Noble said.
Further analysis showed that high sugar intake led to increased levels of parabacteroides in the gut microbiome. When researchers increased levels of the bacteria in the microbe of rats who had never consumed sugar, they discovered the rodents had diminished functionality in hippocampal-dependent and hippocampal-independent memory tasks.
“(The bacteria) induced some cognitive deficits on its own,” Noble said. She added that more research is needed to better distinguish the precise pathways that the gut-brain signaling functions.