Sugar practically screams from the shelves of your grocery store, especially
those products marketed to kids.
Children are the highest consumers of added sugar, even as high-sugar diets
have been linked to health effects like obesity and heart disease and even
impaired memory function.
However, less is known about how high sugar consumption during childhood
affects the development of the brain, specifically a region known to be
critically important for learning and memory called the hippocampus.
New research led by a University of Georgia faculty member in collaboration
with a University of Southern California research group has shown in a
rodent model that daily consumption of sugar-sweetened beverages during
adolescence impairs performance on a learning and memory task during
adulthood. The group further showed that changes in the bacteria in the gut
may be the key to the sugar-induced memory impairment.
Supporting this possibility, they found that similar memory deficits were
observed even when the bacteria, called Parabacteroides, were experimentally
enriched in the guts of animals that had never consumed sugar.
“Early life sugar increased Parabacteroides levels, and the higher the
levels of Parabacteroides, the worse the animals did in the task,” said
Emily Noble, assistant professor in the UGA College of Family and Consumer
Sciences who served as first author on the paper. “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.”
Guidelines recommend limiting sugar
The Dietary Guidelines for Americans, a joint publication of the U.S.
Departments of Agriculture and of Health and Human Services, recommends
limiting added sugars to less than 10 percent of calories per day.
Data from the Centers for Disease Control and Prevention show Americans
between the ages 9-18 exceed that recommendation, the bulk of the calories
coming from sugar-sweetened beverages.
Considering the role the hippocampus plays in a variety of cognitive
functions and the fact the area is still developing into late adolescence,
researchers sought to understand more about its vulnerability to a
high-sugar diet via gut microbiota.
Juvenile rats were given their normal chow and an 11% sugar solution, which
is comparable to commercially available sugar-sweetened beverages.
Researchers then had the rats perform 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,” Noble said.
A second memory task measured basic recognition memory, a
hippocampal-independent memory function that involves the animals’ ability
to recognize something they had seen previously.
In this task, sugar had no effect on the animals’ recognition memory.
“Early life sugar consumption seems to selectively impair their hippocampal
learning and memory,” Noble said.
Additional analyses determined that high sugar consumption led to elevated
levels of Parabacteroides in the gut microbiome, the more than 100 trillion
microorganisms in the gastrointestinal tract that play a role in human
health and disease.
To better identify the mechanism by which the bacteria impacted memory and
learning, 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,” Noble said.
Noble said future research is needed to better identify specific pathways by
which this gut-brain signaling operates.
“The question now is how do these populations of bacteria in the gut alter
the development of the brain?” Noble said. “Identifying how the bacteria in
the gut are impacting brain development will tell us about what sort of
internal environment the brain needs in order to grow in a healthy way.”
Reference:
Emily E. Noble, Christine A. Olson, Elizabeth Davis, Linda Tsan, Yen-Wei
Chen, Ruth Schade, Clarissa Liu, Andrea Suarez, Roshonda B. Jones, Claire de
La Serre, Xia Yang, Elaine Y. Hsiao, Scott E. Kanoski. Gut microbial taxa
elevated by dietary sugar disrupt memory function. Translational Psychiatry,
2021; 11 (1) DOI:
10.1038/s41398-021-01309-7
Tags:
Biology & Health