Sugar practically screams off the shelves of your grocery store, especially products sold to children.
Children are the biggest consumers of added sugar, although high-sugar diets have been linked to health effects such as obesity and heart disease, and even impaired memory function.
However, less is known about how high sugar intake in childhood affects brain development, especially a region known to be critically important for learning and memory called the hippocampus.
New research conducted by a faculty member at the University of Georgia in collaboration with a research group from the University of Southern California has shown in a rodent model that the daily consumption of sugary drinks during adolescence impairs the performance of a learning and memory task in adulthood. The group further showed that changes in bacteria in the gut may be the key to sugar-induced memory impairment.
Supporting this possibility, they found that similar memory deficits were seen even when bacteria, called Parabacteroides, were experimentally enriched in the intestines of animals that had never consumed sugar.
“Sugar early in life increased Parabacteroides levels, and the higher the levels of Parabacteroides, the harder the animals did in the task,” said Emily Noble, assistant professor at UGA College of Science in Medicine. family and consumerism that served as the first author on the paper. “We found that the bacteria alone was sufficient to impair memory in the same way as sugar, but also impaired other types of memory functions.
Guidelines recommend limiting sugar
The Dietary Guidelines for Americans, a joint publication of the U.S. departments of agriculture and 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 shows Americans between the ages of 9 and 18 exceed this recommendation, with the bulk of calories coming from sugary drinks.
Considering the role played by the hippocampus in various cognitive functions and the fact that the region is still developing until late adolescence, the researchers sought to better understand its vulnerability to a diet high in sugar via the microbiota. intestinal.
Juvenile rats were given their normal food and an 11% sugar solution, which is comparable to commercially available sugary drinks.
The researchers then asked the rats to perform a hippocampal-dependent memory task designed to measure episodic contextual memory or remember the context in which they had seen a familiar object before.
“We found that rats that consumed sugar early in their life had a reduced ability to distinguish that an object was new in a specific context, a task that rats that were not given sugar were able to do. Noble said.
A second memory task measured baseline recognition memory, a hippocampal-independent memory function that involves the ability of animals to recognize something they had previously seen.
In this task, sugar had no effect on the recognition memory of the animals.
“Consuming sugar early in life appears to selectively impair their learning and hippocampal memory,” Noble said.
Further analysis determined that high sugar consumption leads to high levels of Parabacteroides in the gut microbiome, the more than 100 trillion microorganisms in the gastrointestinal tract that play roles in human health and disease.
To better identify the mechanism by which bacteria impacted memory and learning, the researchers experimentally increased the levels of Parabacteroides in the microbiome of rats that had never consumed sugar. These animals exhibited both hippocampal-dependent and hippocampal-independent memory impairment.
“(The bacteria) alone caused some cognitive deficits,” Noble said.
Noble said more research is needed to better identify the specific pathways through which this gut-to-brain signaling works.
“The question now is how do these populations of bacteria in the gut alter brain development?” Said Noble. “Identifying the impact of bacteria in the gut on brain development will tell us about the type of internal environment the brain needs to develop in a healthy way.
The article, “Intestinal microbial taxa elevated by dietary sugar disrupts memory function,” appears in Translational Psychiatry. Scott Kanoski, associate professor at USC Dornsife College of Letters, Arts and Science, is the corresponding author of the article.
The other authors of the article are Elizabeth Davis, Linda Tsan, Clarissa Liu, Andrea Suarez and Roshonda B. Jones of the University of Southern California; Christine Olson, Yen-Wei Chen, Xia Yang and Elaine Y. Hsiao of the University of California-Los Angeles; and Claire de La Serre and Ruth Schade from UGA.