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TUESDAY, July 20 (HealthDayNews) -- Researchers trying to prevent bone loss in women with cirrhosis of the liver have made an unexpected yet welcome discovery -- that vitamin K may help prevent liver cancer in those most at risk of the disease.

The study, which appears in the July 21 issue of the Journal of the American Medical Association, was originally designed to assess the effects of vitamin K supplementation on bone loss in women with viral cirrhosis of the liver. However, at the end of the study, the researchers realized the women who took the vitamin K had significantly lower rates of liver cancer.

"The results suggest a possible role for vitamin K2 in the prevention of liver cancer in women with viral cirrhosis," said study co-author Dr. Susumu Shiomi, a professor of nuclear medicine at the Graduate School of Medicine at Osaka City University in Japan. Shiomi added that "vitamin K2 is cheap and safe to use."

Dr. Jay Brooks, chief of hematology/oncology at Ochsner Clinic Foundation Hospital in New Orleans, explained that people with viral cirrhosis from diseases such as hepatitis C are at an increased risk of developing liver cancer. While researchers still don't know why, Brooks said, "we do know that they run an incredibly increased risk." And, he said, the problem will likely only increase because hepatitis C is being diagnosed in more people.

Between 1996 and 1998, 40 women with viral cirrhosis were recruited for a study in preventing bone loss. The women were randomly assigned to either the treatment group or the placebo group. The treatment group took a pill containing 45 milligrams of vitamin K2 daily.

Vitamin K is a fat-soluble vitamin that is produced in the intestines. It can also be found in leafy green vegetables such as broccoli and spinach, vegetable oils, cereals and some meats and cheeses. Excess amounts of this vitamin are stored in the liver. The recommended daily allowance of vitamin K in the United States is 75 micrograms to 90 micrograms (a thousandth of a milligram) per day for women and 75 micrograms to 120 micrograms for men.

Most of the women enrolled in the study had hepatitis C. The average age of the study participants was around 60.

Two of 21 women in the treatment group developed liver cancer, while nine out of 19 women in the placebo group did. After adjusting for age, severity of disease and treatment, the researchers found the women receiving vitamin K supplementation were nearly 90 percent less likely to develop liver cancer.

The researchers said it wasn't clear how vitamin K could prevent liver cancer, but theorized that it may dampen cancer cell growth.

"A number of findings indicate that vitamin K2 may play a role in controlling cell growth. But the mechanisms responsible for the vitamin K-mediated inhibition of cell growth remains unexplained," Shiomi said.

"It's an interesting early observation, but it's a very small study," Brooks said. Both the authors of the study and Brooks said these results need to be confirmed with a much larger group of people.

And, Brooks added, "it would be extremely premature for anyone with hepatitis C to start taking vitamin K." He said that in the past there have been studies on vitamins that initially looked promising in the prevention of cancer, but then with further study, were found to be ineffective or, worse, harmful.

More information

To learn more about vitamin K, visit the U.S. Department of Agriculture's Agricultural Research Service.

(SOURCES: Susumu Shiomi, M.D., professor, nuclear medicine, Graduate School of Medicine, Osaka City University, Osaka, Japan; Jay Brooks, M.D., chief, hematology/oncology, Ochsner Clinic Foundation Hospital, New Orleans; July 21, 2004, Journal of the American Medical Association)

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