New research out of Yale University indicates that the human brain can convert one type of sugar, glucose, into another type, fructose.
You are likely familiar with fructose from the much maligned, hilariously defended (more hilariously spoofed), and ubiquitous high fructose corn syrup. Fructose is also found in fruits, honey, agave, and table sugar.
Previous studies indicate that glucose and fructose have markedly different effects on the brain. Specifically, glucose prompts feelings of fullness and satiety while fructose does not. Additionally, high intake of fructose is associated with increased risk of obesity and type II diabetes. This is the first evidence of the brain actually converting glucose into fructose.
“In this study, we show for the first time that fructose can be produced in the human brain,” said first author Janice Hwang, M.D., assistant professor of medicine.
While the production of fructose in the brain had been seen in animals, it had not been demonstrated in humans, Hwang noted.
The research team gave eight healthy, lean individuals infusions of glucose over a four-hour period. They measured sugar concentrations in the brains of the study participants using magnetic resonance spectroscopy, a noninvasive neuroimaging technique. Sugar concentrations in the blood were also assessed.
The researchers found cerebral fructose levels rose significantly in response to a glucose infusion, with minimal changes in fructose levels in the blood. They surmised that the high concentration of fructose in the brain was due to a metabolic pathway called the polyol pathway that converts glucose to fructose.
This research is useful because it shows that fructose can be present in the brain regardless of consumption.
“By showing that fructose in the brain is not simply due to dietary consumption of fructose, we’ve shown fructose can be generated from any sugar you eat,” said Hwang. “It adds another dimension into understanding fructose’s effects on the brain.”
This was a rather small study and the researchers were indirectly measuring brain fructose levels. Obviously, further research will need to be done to both confirm the implications of this research and to expand upon it. If confirmed, it will lead to more insight as to how high blood glucose levels effect the brain.
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