High-calorie diet, not sugar intake, promotes the progression of nonalcoholic fatty liver disease (NAFLD), according to research findings. The researchers conducted a double-blind study of healthy but centrally overweight men to compare the effects of two types of sugar – glucose and fructose – in two conditions: weight maintaining and weight gaining.
In the weight-maintaining period, men did not develop any significant changes to the liver, regardless of their diet (moderate-calorie vs. high-calorie diet). In the weight-gaining period, however, both diets produced equivalent features of nonalcoholic fatty liver disease.
Study author Prof. Ian A. Macdonald said, “Based on the results of our study, recommending a low-fructose or low-glycemic diet to prevent nonalcoholic fatty liver disease is unjustified. 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.”
In a recent study supported by the National Institutes of Health and the U.S. Department of Agriculture, scientists from Oregon State University found that liver damage caused by the typical Western diet may be difficult to reverse. The study shows that while a diet with reduced fat, sugar, and cholesterol helped the liver, it did not fully resolve liver damage that had already been done.
To make matters worse, the irreversible damage can lead to secondary complications like cirrhosis of the liver and even malignancy.
This study, published in PLOS ONE, was conducted on laboratory animals. The results showed that diets low in fat and cholesterol could help with weight loss, and improved metabolism and health. But if the diet has a high sugar content, the chances of liver recovery were considerably reduced.
Liver issues such as NAFLD are on the rise in the U.S., affecting 10 to 35 percent of adults and an increasing number of children. These numbers can go up to 60 percent in obese population and type 2 diabetics. In light of these numbers, the findings of the study are very significant.
According to Donald Jump, a professor in the OSU College of Public Health and Human Sciences, many people eating a common American diet rich in unhealthy fats, cholesterol, and sugar, are developing extensive scarring of their liver. Prof. Jump believes this kind of liver scarring is the first step towards a reduced liver function and can even lead to cancer.
There has been a lot of research done aiming to identify a causative link between unhealthy foods and liver damage. And while the causality is there, abstaining from a fatty, cholesterol-rich diet, unfortunately, is not enough to slow down the damage. For that to happen, the intake of sugar has to come down, too, but even then it is still questionable whether the damage can be reversed.
For the study, the scientists analyzed two groups of laboratory mice that had been fed a Western diet and then switched to different, healthier diets.
Both of the healthier diets were low in fat and cholesterol, but one of the groups continued with a high sugar intake.
Both of the improved diets brought on health improvements and weight loss. However, the group that was fed a high sugar diet had significantly higher levels of inflammation, oxidative stress, and liver fibrosis.
Based on these results, it is obvious that the presence of sugar in the diet plays a key role in the liver damage and is inversely correlated with the speed of liver recovery: the greater the sugar intake, the slower the recovery.
The team believes more complex studies are required to determine whether a comprehensive program of diet, weight maintenance, and exercise in combination with specific drugs can fully resolve scarring of the liver.
Because a fatty liver can contribute to diabetes and lead to cirrhosis and liver failure, it’s important to take the necessary steps to prevent fatty liver. Here’s what you can do: