It’s well known that too much sugar is bad for you. There are complications from a high sugar diet that include diabetes, obesity and cardiac issues. When food is ingested, the body converts what it needs for energy into a simple sugar, glucose. Glucose is needed in the cells to make muscles work efficiently and it’s needed in the brain for cognition and synapses. The problem begins when there is too much glucose to be absorbed into the cells. When that happens, and the cells of the body are at capacity, any excess glucose spills over into the bloodstream. High levels of circulating glucose will eventually cause a person to develop diabetes, gain weight and have other symptoms, so it’s best to maintain a healthy diet.
There are other sugars produced in the body however and they don’t all act equally. Recent research at Yale University has shown that the human brain actually produces its own sugar, but not glucose. The team at Yale has published a study that shows, via specific MRI scans, that the brain produces fructose when blood glucose levels increase. Fructose is a sugar that occurs naturally in some foods and is added to others in the form of high fructose corn syrup. The results from the Yale study are the first to show that it is produced in the brain.
So how does it work? When glucose levels become elevated in the body, in addition to causing high blood sugar and other complications, some of the glucose is converted into fructose, using a process known as the “polyol pathway.” This pathway is a chemical reaction that is often seen in diabetics when their blood sugar levels fluctuate or are not well controlled. The team at Yale reported that their research shows the polyol pathway is at work in the brain and it results in fructose being produced there. Unlike glucose levels in the blood, levels of fructose are usually low, even when glucose is high. Fructose is metabolized almost entirely by the liver so the levels found in the brain are not likely to be the result of fructose in the bloodstream making its way to the brain.
The study involved 8 volunteers, all of whom were healthy, with no cardiovascular problems, diabetes or obesity. After an intravenous infusion of glucose, they underwent a very specific MRI brain scan known as Magnetic Resonance Spectroscopy, or MRS. It differs from a traditional MRI because it’s able to provide researchers with biochemical information about the tissues in the brain, rather than just structural information. In the Yale study, 20 minutes after being given glucose via the IV, the MRS scans showed marked increases in fructose levels in the brain, levels that could not have been elevated as a result of fructose circulating in the bloodstream. The fructose was coming from inside the brain.
In a press release about the study, first author Dr. Janice Hwang, assistant professor of medicine at the university said, “In this study, we show for the first time that fructose can be produced in the human brain. 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. It adds another dimension into understanding fructose’s effects on the brain.” Take a look at the video below to learn more about the study.