Despite what you may have read in the New York Times and other mainstream media outlets jumping on the 'sugar is bad' fad, sugar intake is off the hook in one area; nonalcoholic fatty liver disease. High-calorie diets promote the progression of this serious form of liver disease, but that isn't a sugar issue, it is a behavioral one.
Nonalcoholic fatty liver disease is the most prevalent liver problem in the U.S. and most Western countries. It is the buildup of extra fat in liver cells that is not caused by alcohol.
Researchers conducted a double-blind study of healthy, but centrally overweight men to compare the effects of high intakes of two types of sugar, glucose and fructose, in two conditions — weight-maintaining (moderate-calorie diet) and weight-gaining (high-calorie diet). In the weight-maintaining period, men on neither diet developed any significant changes to the liver. However, in the weight-gaining period, both diets produced equivalent features of nonalcoholic fatty liver disease, including steatosis (fatty liver) and elevated serum transaminase and triglycerides. These findings indicate that fructose and glucose have comparable effects on one's liver, and calorie intake is the factor responsible for the progression of liver disease.
"Based on the results of our study, recommending a low-fructose or low-glycemic diet to prevent nonalcoholic fatty liver disease is unjustified," said Professor Ian A. Macdonald, senior author of the study on the faculty of medicine and health sciences at the University of Nottingham. "The best advice to give a patient is to maintain a healthy lifestyle with diet and exercise. Our study serves as a warning that even short changes in lifestyle can have profound impacts on your liver."
During the period of increased calorie intake, all study participants experienced significant increases in body weight, waist circumference and total body fat, as expected. Interestingly, satiety was unaltered in spite of weight gain during the high-calorie diet; this reinforces the notion of "hidden calories" in drinks since participants consumed a portion of their calories in liquid form.
Fructose is a simple sugar commonly found in fruits and vegetables. Glucose, also known as grape or blood sugar, is present in all major carbohydrates, such as starch and table sugar.
Citation: Richard D. Johnston, Mary C. Stephenson, Hannah Crossland, Sally M. Cordon, Elisa Palcidi, Eleanor F. Cox, Moira A. Taylor, Guruprasad P. Aithal, Ian A. Macdonald, 'No Difference Between High-Fructose and High-Glucose Diets on Liver Triacylglycerol or Biochemistry in Healthy Overweight Men', Gastroenterology, Volume 145, Issue 5, November 2013, Pages 1016-1025.e2 DOI: 10.1053/j.gastro.2013.07.012
More on how to prevent Nonalcoholic fatty liver disease: "NAFLD Treatment: Is there More to Talk About Other than Diet and Exercise?"- AGA Perspectives