Researchers at the University of California, Irvine, have found that fructose's role in obesity may go beyond its calorie content. Processing this sugar in the gut can alter the microbiome and enhance fat absorption from food, reports infohub.kz.
In the study, the scientists focused on the small intestine, where fructose is primarily metabolized. To investigate the process, they conducted a series of controlled experiments on mice, using a highly active form of the enzyme that breaks down fructose.
Over 12 weeks, one group of rodents was given drinking water with a high concentration of corn syrup rich in fructose, while the other group received plain water without added sugar. The researchers tracked body weight, fat deposits, and blood glucose levels, as well as measured fat absorption. To do this, they administered a dose of soybean oil and monitored how much fat entered the bloodstream versus how much was excreted.
Separately, they studied mice lacking the enzyme KHK-C, which is involved in fructose processing specifically in the gut. Despite equal calorie intake, these animals gained significantly less weight and fat, and also had better blood sugar control.
The results showed that altering fructose metabolism affected the gut microbiome and led to shortening of lacteals—lymphatic vessels responsible for absorbing dietary fats. Consequently, the experimental mice absorbed less fat and excreted more.
Next, the researchers transplanted the altered microbiome into normal mice, which also exhibited changes in lacteals and reduced fat absorption. This suggested that fructose may influence weight gain not only through calories but also through a chain involving the gut, microbiome, and fat absorption.
The authors emphasize that for humans, this means fructose's impact on body weight may be more complex than just "extra calories." It is hypothesized that high amounts of fructose, especially when combined with fatty foods, could enhance fat absorption through the gut and microbiome. However, these findings are from mice, and it remains unknown whether a similar mechanism operates in humans.