High-fructose corn syrup has taken a lot of blame for global epidemics of obesity and diabetes. Some say too much fructose in any form is especially dangerous because it stresses the liver—the only organ in the body that can metabolize it. A new study supports this claim by finding that heavy fructose intake can cause an energy imbalance in the liver that can lead to non-alcoholic fatty liver disease.
Fructose vs. sugar
Fructose consumption has more than doubled in the past 30 years in the U.S. During the same period, the rate of non-alcoholic fatty liver disease has increased just as fast as rates of type 2 diabetes and obesity.
Fructose is a sugar found naturally in fruits, vegetables, and honey. When fructose and glucose molecules join, you get sucrose. Sugar cane, sugar beets, corn, and other plants are rich in sucrose. Table sugar is refined sucrose.
High-fructose corn syrup molecules are virtually identical to refined sugar molecules. But although every cell in the body can metabolize glucose and sucrose, only the liver can metabolize fructose. Because of this, overconsumption, which is made especially easy with high fructose corn syrup in sugary drinks, can lead to a condition called nonalcoholic fatty liver disease (NAFLD). NAFLD affects up to one-third of Americans.
Byproducts of fructose metabolism in liver cells are triglycerides and uric acid. Triglycerides can build up to impair liver function, overflow into the bloodstream and contribute to arterial plaque. Excess uric acid can impair production of nitric oxide, a substance that helps protect artery walls.
Energy depletion in the liver
In a study investigating the link between fructose and the risk of NAFLD, researchers at Duke University Medical Center found that high fructose intake was associated with lower levels of adenosine triphosphate (ATP), a compound involved in energy transfer between liver cells. They also found that higher uric acid levels from excess fructose further depleted ATP in the liver. Severely depleted ATP delayed its rebound to safe normal levels after a fructose spike, which happens with consumption of a sugary beverage.
In a report on the study published in the journal Hepatology, the researchers suggested that these dual effects of excessive fructose consumption cause energy depletion in the liver that might be a factor in the development and progression of NAFLD.
People with NAFLD often don’t realize it. But the longer they have it, the more likely it will progress into more serious conditions such as liver fibrosis (accumulation of abnormal fibrous tissue), cirrhosis (accumulation of scar tissue), liver failure and ultimately death.
The best preventive strategy for NAFLD is to pay careful attention to diet and exercise. Swearing off sugary drinks sweetened with fructose is the best place to start.