A glass or two of orange, grapefruit or other citrus juice each day may help prevent osteoporosis-linked bone fracture, a new U.S. study in rats concludes.

Regular doses of grapefruit and orange juice helped prevent osteoporosis and strengthened bones in a study conducted on male rats with low levels of circulating testosterone.

"This is a problem with aging men, because the level of testosterone decreases as men age," lead researcher Dr. Farzad Deyhim, a professor of human and animal nutrition at Texas A & M-Kingsville, said in a prepared statement.

His team at the Vegetable and Fruit Improvement Center divided the rats into three groups: those with no change in diet; those who received orange juice; and those who received grapefruit juice. The rodents were fed fresh juice supplemented with sodium bicarbonate, to reduce acidity, every morning.

The juice-fed rats showed enhanced bone density, the researchers report in the current issue of Nutrition.

The next step for the researchers is to study the cellular makeup of the rats' bones to determine how the juice actually improved bone strength. "There are about 400 compounds in citrus, so we need to find out which compound in citrus caused this," said Dr. Bhimu Patil, director of the university's center.

"A reduction in bone density is caused when there is an increase in oxidants. In these studies, both grapefruit juice and orange juice increased antioxidants in the rats' systems," Patil said. "So that is the benefit since oxidants damage bone cells."

There are about 1.5 million fractures in the United States every year caused by osteoporosis, says Patil. "It's a silent disease of aging. But if we can maintain our bone strength, maybe we'll be able to prevent it."