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Sept. 19, 2008 -- A high intake of vitamin C may help reduce bone loss, at least in elderly men, according to a new study.
"Vitamin C had an effect on the [bone density of] hips in men, but it didn't have an effect on women," says Katherine L. Tucker, PhD, a senior scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University and senior author of the study. It is published in the Journal of Nutrition.
For years, researchers have known that vitamin C is needed for normal bone development and for the formation of collagen, the fibrous protein part of bone, cartilage, and other structures.
But few studies have looked at the relationship between vitamin C intake from food and supplements and bone density, Tucker says.
Vitamin C is an antioxidant vitamin and reduces oxidative stress, which has a negative effect on all cells in the body, she says. "Antioxidants are needed to protect against oxidative stress, therefore protecting against inflammation. Inflammation drives bone resorption, which is basically taking calcium away from the bones. Vitamin C, theoretically, should help slow that resorption."
Tucker and her colleagues evaluated the bone density of 213 men and 393 women, average age 75 at the start, over a four-year period to see what association their vitamin C intake had with their bones.
The participants were part of the long-running Framingham Osteoporosis study. The researchers looked at a diet questionnaire given to participants in 1988 or 1989 and again four years later. They evaluated the change in bone density in the hips, spine, and arm over the follow-up. Besides looking at their vitamin C and vitamin E intake, they took into account whether participants smoked and whether the women were on hormone replacement therapy.
Men with the highest vitamin C intake had the least bone loss in the hip. A similar finding in women was not significant, Tucker says.
The effect became most significant, she says, at the highest level, about 314 milligrams of vitamin C daily from supplements and food. The recommended intake is 75 milligrams daily for women and 90 milligrams daily for men.
"At one hip site [of two measured], for example, men in the highest intake group, who took in 314 milligrams of vitamin C a day in food and supplements but had low calcium intake, did not lose bone density on average," she says, ''whereas those in the lowest group, who took in 106 milligrams, lost 5.6% of their bone."
"The only significant effects on bone loss were found in men who were low in vitamin E or calcium," she says.
Why no effect was not seen in women is complicated, Tucker says. The effects of vitamin C may interact with estrogen use, calcium, and vitamin E, she notes.