Fructose is found in fruits, vegetables, table sugar and many processed foods, but now scientists are reporting that the brain naturally produces fructose, a type of sugar associated with obesity and type 2 diabetes.
The Yale University researchers said follow-up studies will investigate how fructose affects the brain and eating behaviour.
The findings were published in the journal JCI Insight.
The controversy of fructose
According to Health24's former DietDoc, Dr Ingrid van Heerden, fructose is a so-called "simple sugar" found in honey, fruit, vegetables and other plant materials. Fructose has been in the spotlight for more than 20 years.
Some researchers link a high intake of fructose to a wide variety of metabolic ills, including obesity, non-alcoholic fatty liver disease, raised uric acid levels and increased triglyceride levels which may cause cardiovascular disease.
On the other hand, other researchers are dedicated to proving that fructose is a sugar like any other, that it has no special effects on disease or expanding waistlines and that any changes in the health of the global population are not due to fructose itself, but are merely due to an increased kilocalorie or kilojoule intake.
How the brain makes fructose
In experiments with eight healthy volunteers, the researchers said they found that fructose is converted in the brain from another simple sugar, glucose.
"In this study, we show for the first time that fructose can be produced in the human brain," said study first author Dr Janice Hwang, an assistant professor of medicine.
"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," Hwang said in a university news release.
In the brain, glucose sends signals of being full, but that's not the case with fructose. The conversion of glucose to fructose also occurs in other parts of the body, the researchers said.
"This pathway may be one other mechanism by which high blood sugar can exert its adverse effects," Hwang said.