LOS ANGELES — People with a common, obesity-related liver disease that has no known treatment got a surprising benefit from vitamin E pills, researchers reported Wednesday.

It appears to be the first time that a vitamin supplement has been shown to help treat a major ailment not caused by a nutrient deficiency. However, doctors warned that this does not mean people should automatically take vitamin E since some research suggests it might raise the risk of other problems.

The latest study tested it for nonalcoholic fatty liver disease. Fat buildup can cause the liver to become scarred over time and in severe cases, to fail.

The disease usually develops in people who are middle-aged and overweight. Up to 5 percent of Americans have the most serious form.

In the study published online in the New England Journal of Medicine, 247 adults with advanced disease were assigned a high dose of vitamin E (800 IU), the diabetes drug Actos or dummy pills for nearly two years.