SAN FRANCISCO • Researchers have found that liver damage caused by the typical "Western diet" may be difficult to reverse even if diet is generally improved.
In a study done by Oregon State University (OSU) with laboratory animals, researchers discovered that a diet with reduced fat and cholesterol could help with weight loss and improved metabolism and health, but did not fully resolve liver damage if the diet was still high in sugar.
The Western diet, which is popular in many parts of the world, was defined by the researchers as high in fat, sugar and cholesterol.
Professor Donald Jump of the OSU College of Public Health and Human Sciences said: "Many people eating a common American diet are developing extensive hepatic fibrosis, or scarring of their liver, which can reduce its capacity to function, and sometimes lead to cancer."
Liver problems, such as non-alcoholic fatty liver disease, are surging in the US, affecting 10 to 35 per cent of adults and an increasing number of children. It can happen to more than 60 per cent in obese and Type 2 diabetic populations.
"Everyone recognises this is a serious problem," said Ms Kelli Lytle, an OSU doctoral candidate and lead author of the study published last week in PLOS ONE, an open-access scientific journal.
"We're trying to find out if some of the types of dietary manipulation that people use, such as weight loss based on a low-fat diet, will help address it," said Ms Lytle.
"However, a common concern is that many low-fat food products have higher levels of sugar to help make them taste better."
In the research, two groups of laboratory mice were fed a Western diet and then switched to different, healthier diets, low in fat and cholesterol.
Both of the improved diets caused health improvements and weight loss.
But one group that was fed a diet still fairly high in sugar - comparable to what is in the Western diet - had significantly higher levels of inflammation, oxidative stress and liver fibrosis.
Complications related to liver inflammation, scarring and damage are projected to be the leading cause of liver transplants by 2020, the researchers noted.
Such scarring was once thought to be irreversible, but more recent research has shown it can be at least partially reversed with optimal diet and when the stimulus for liver injury is removed.
"For more significant liver recovery, the intake of sugar has to come down, probably along with other improvements in diet and exercise," said Prof Jump.
The researchers acknowledged that more studies are needed to determine whether a comprehensive programme of diet, weight maintenance, exercise and targeted drug therapies can fully resolve liver fibrosis.
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