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.”
Source: https://news.uga.edu/sugar-not-so-nice-childs-brain-development/
Journal article: https://www.nature.com/articles/s41398-021-01309-7
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