The Grapevine

Liver Damage Causes: High Fructose Intake Could Be One

Food manufacturers opt for high fructose corn syrup ( combination of glucose and fructose)  in the process of adding sugars for economical reasons. Usage of fructose to artificially sweeten food has gained popularity since the 1970s.

It has become controversial in nature recently since fructose is known to cause diabetes, obesity, heart problem and non-alcoholic fatty liver disease. In most cases, fructose is more harmful than table sugar (sucrose), several studies in the past have said. 

A new study by Joslin Diabetes Center, an affiliate of the Harvard Medical School, found that the liver’s capacity to metabolize or burn fat was compromised with a high intake of the high-fructose diet. Though they may contain the same calories, glucose was shown to aid the liver’s metabolism. 

Researchers experimented with animals in a series of studies by allocating to them six diets with various levels of sugar and fat. Animals were fed different variations of chow such as regular chow, chow with high glucose and chow with high fructose. Other diets included a regular high-fat diet, a high-fat diet with high fructose and a high-fat diet with glucose. 

To understand the impact of fructose on metabolism, markers for fatty liver and enzymes that aid metabolism were checked in the animals based on their diet. Levels of acylcarnitines indicate the liver’s ability to burn fat and was used to guage the function. 

High levels of acylcarnitines mean that fat is accumulating in the liver. Acylcarnitines were found the highest among the animals on the high-fat and high-glucose diet. Surprisingly, glucose did not increase the acylcarnitines level since the animals on the high-fat and high-glucose diet had much lower levels of the important marker, even in comparison to the animals on the regular high-fat diet.

This finding showed the researchers that glucose played a role in burning fat in the liver and confirmed previous observational studies that had indicated the same. Another aspect the researchers looked into was CPT1a levels, which is an enzyme required to burn fat.

On the high-fat and high-fructose diet, CPT1a levels were down and their activity was limited, which goes to show that mitochondria processes might be affected. Mitochondria are the powerhouses of each cell that absorb, digest and break down nutrients.

"When mitochondria are healthy, they have this nice ovoid shape and crosshatching. In the high-fat plus fructose group, these mitochondria are fragmented and they're not able to burn fat as well as the healthy mitochondria. But looking at the high-fat diet plus glucose group, those mitochondria become more normal looking because they are burning fat normally," Ronald Kahn, Chief Academic Officer at Joslin Diabetes Center said in the press release.

Kahn is the lead author of the study published in Cell Metabolism on October 1. The solution that Kahn and his colleagues believe that will work best is a drug, which blocks the metabolism of fructose, prevents fatty liver disease and improves glucose tolerance. 

Fructose vs. Sucrose Researchers determine if fructose is really more toxic than sucrose. Photo courtesy of Shutterstock