VITAMIN E supplements may cause thinning of the bones, new research suggests.
The early findings, from animal studies, indicate that the most common form of vitamin E stimulates the generation of bone-degrading cells.
Scientists who carried out the research in Japan are now calling for their results to be followed up in humans.
Thousands of people here take supplements of vitamin E, a powerful antioxidant. In the US, more than 10pc of adults take the vitamin every day.
The most common form of the vitamin, both in supplements and natural sources such as olive and sunflower oil, is alpha-tocopherol.
Its health benefits are said to include reducing the risk of heart disease, cancers, cataracts and age-related mental decline, but the evidence is patchy.
The new research focused on bone "remodelling" -- the maintenance of bone by balancing its formation and breakdown.
When bone is broken down, specialist osteoclast cells cause its minerals to be released and recycled into the body in a process called "resorption". The study suggests that while vitamin D promotes bone generation, alpha-tocopherol vitamin E performs the opposite role.
Researchers led by Dr Shu Takeda, from Keio University in Tokyo, found that genetically modified mice with low blood levels of the vitamin developed excessively high bone mass.
This was found to be due to lower levels of bone resorption, rather than greater bone formation.
When vitamin E was added to the animals' diet, their bone density returned to normal.
Normal mice given alpha-tocopherol vitamin E supplements at doses equivalent to those taken by humans showed a 20pc reduction in bone mass after eight weeks. The same result was seen in rats.
However, the effect did not occur when animals were given the less common delta-tocopherol form of vitamin E, which showed it had nothing to do with antioxidant properties common to all versions of the vitamin.
The findings are published in the journal Nature Medicine.