TORONTOFructose itself is not responsible for increases in non-alcoholic fatty liver disease (NAFLD), according to new research published in the European Journal of Clinical Nutrition. Researchers found an excess consumption of calories can contribute to the disease, regardless of whether those calories came from fructose or other carbohydrates.

John Sievenpiper, a researcher in the Clinical Nutrition and Risk Factor Modification Centre of St. Michaels Hospital, led a team from St. Michael's in performing a meta-analysis on all available human trials. Sievenpiper said fructose behaves no differently than glucose or refined starches, and it's only excess calories in the form of fructose that cause harm.

NAFLD is the most common chronic liver disease in developed countries, affecting up to 30% of their populations. Because the disease is closely linked to obesity and type 2 diabetes, theres a growing debate in the medical community about whether diet plays a role in its development, specifically the consumption of fructose.

The possible link to NAFLD has become a main criticism against fructose among those who believe there is something unique about the fructose molecule or the way it is metabolized and blame it for the obesity epidemic.

Fructose, which is naturally found in fruit, vegetables and honey, is a simple sugar that together with glucose forms sucrose, the basis of table sugar. It is also found in sucrose and high-fructose corn syrup, the two most common sweeteners in commercially prepared foods.

NAFLD is one cause of a fatty liver, occurring when fat is deposited in the liver. Unlike alcoholic liver disease, it is not due to excessive alcohol use.

Previous research by Sievenpiper indicates that fructose by itself does not cause weight gain and does not itself have any impact on an emerging marker for the risk of cardiovascular disease known as postprandial triglycerides when it is substituted for other carbohydrates. It is when fructose is over-consumed and provides excess calories that you see the adverse effects on health, but no more than when other carbohydrates are over-consumed.

Sievenpiper's previous research shows no benefit in replacing fructose with glucose in commercially prepared foods. That research again showed that that when portion sizes and calories are the same, fructose does not cause any more harm than glucose.

The debate over the role of fructose in obesity, fatty liver and other metabolic diseases has distracted us from the issue of overconsumption," Sievenpiper said. Our data should serve to remind people that the excess calories, whether they are from fructose or other sources, are the issue."