New medical research suggests that high doses of vitamin E can cause "bone-stripping", or the loss of bone mass, and that people taking supplements are potentially exposing themselves to increased risk of fracture.
Scientists at the Keio University in Tokyo , Japan, tested the effects of vitamin E supplements on mice, and found that high doses of the nutrient stimulated the production of bone-eroding cells, the BBC News reported this week.
The study, which was published in the journal Nature Medicine, showed that the mice who were deficient in vitamin E at the start of the trial, actually had better bone health before they were given supplements, after which they lost bone mass.
Vitamin E is a broad name for a group of fat-soluble compounds with high anti-oxidant properties. It occurs naturally in foods like spinach, almonds and sunflower seeds, is also added to other foods, and produced in supplement form.
The health benefits of vitamin E are thought to include the reduced risk of heart disease, cancers, and cognitive decline, the alleviation of inflammation, and promotion of immune function and eye health.
Based on prior studies, vitamin E was also previously believed to be beneficial to bone health, principally due to its strong antioxidant properties, but the new research suggests otherwise.
The maintenance of good bone health during adulthood is determined by the balance between bone-forming cells (osteoblasts) and bone-degrading cells (osteoclasts).
Lead researcher on the project, Shu Takeda, said that the nutrient threw off this balance by spiking production of the bone-degenerating osteoclasts, and called for further studies on humans to be carried out.
"We show that vitamin E stimulates bone resorption and decreases bone mass by inducing osteoclast fusion," wrote the researchers. "Moreover, we provide evidence that serum vitamin E is a determinant of bone mass.
"Given the widespread use of vitamin E, and especially alpha-tocopherol, as a supplement in humans, a larger, controlled study that addresses its effects on human bone is warranted."
Dr Helen Macdonald of Aberdeen University in the UK said that her own research on the influence of nutrition on bone health confirms the negative effects of vitamin E supplements.
"Vitamin E supplements involve doses far higher than those in a normal diet," she said. "There is increasing evidence that taking supplements doesn't do any good, and if anything, may be doing harm."
But other medical experts are less certain about the results of the new research and maintain that further studies need to be conducted.
The study has revealed "the opposite of what was traditionally believed," according to Dr Robert Graham, an internist at Lenox Hill Hospital in New York City.
"This is intriguing, because previous in vitro [laboratory] studies and mice studies have yielded contradictory results."
Graham added that: "Before we start telling people to throw away their vitamin E, let me state that these results are in mice and more studies are needed to see the risks and benefits in humans."