A diet high in high fructose corn syrup during pregnancy may leave a lasting biological imprint on a baby's developing brain, according to new research from Japan that found learning and memory problems persisted into adulthood in rats exposed to excess fructose before birth. While the findings come from an animal study and do not prove the same effect occurs in humans, researchers say they offer fresh clues about how a mother's diet could shape long-term brain health.

The study, published in Stem Cell Reports by scientists at Fujita Health University School of Medicine in Toyoake, Japan, and highlighted by the International Society for Stem Cell Research (ISSCR), investigated why prenatal exposure to high fructose appears to have long-lasting effects on the brain.

Inside the laboratory, researchers fed pregnant rats a diet rich in high fructose corn syrup before examining the brains of their offspring. As adults, these rats performed significantly worse in standard tests that measured learning, memory and spatial navigation than animals whose mothers ate a normal diet.

The team traced these changes to neural stem cells—the master cells that generate new brain cells throughout life. In regions of the brain responsible for learning and memory, particularly the hippocampus, the process of neurogenesis, or the production of new brain cells, was markedly reduced.

When the researchers isolated these stem cells for closer examination, they found they divided more slowly, produced fewer healthy neurones and displayed widespread disruptions in gene activity. Further analysis revealed changes in epigenetics—chemical tags attached to DNA that regulate how genes work without altering the genetic code itself.

These molecular markers appeared during foetal development and remained throughout adulthood, effectively suppressing development and silencing genes needed for healthy brain development.

"Our study suggests that neural stem cells may retain a biological memory of maternal nutrition during pregnancy," said Dr Hiroya Yamada. "This may help explain how a transient prenatal dietary imbalance can lead to long-lasting changes in brain development and function."

In an encouraging laboratory experiment, the scientists restored normal activity in the affected genes. Once the restoration happened, the damaged stem cells regained much of their ability to divide and generate new brain cells, suggesting that at least some of the biological damage could be reversible.

The findings build on previous human observational studies that have linked high consumption of sugary drinks during pregnancy with poorer cognitive outcomes in children. However, such studies show associations rather than direct cause and effect. Scientists have also long acknowledged that maternal nutrition influences foetal development and the subsequent risk of obesity, diabetes, and heart disease.

The researchers caution that further studies are needed to determine whether human neural stem cells respond to excess fructose in the same way. Even so, the work provides one of the clearest biological explanations yet for how an unhealthy pregnancy diet could leave a lasting molecular "memory" in the developing brain, reinforcing public health advice that balanced nutrition during pregnancy benefits both mother and child.