"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.
Vitamin C and Bones: Background
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."
Vitamin C and Bones: Study Detail
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.
Vitamin C and Bones: Study Results
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.
Vitamin C and Bones: Second Opinion
The new finding is "interesting and plausible," says Robert P. Heaney, MD, professor at John A. Creighton University in Omaha and a longtime researcher in osteoporosis.
"There is good biology behind it," he says. "If you don't have enough vitamin C, you don't make bones right. Collagen is the principal protein of bones, accounting for nearly half the volume. What the collagen does is prevent bones from coming apart."
In recent years, says Heaney, researchers have found that maintaining bone density requires not just getting enough calcium, but also vitamin D and protein. Now, more evidence is emerging about the important role of vitamin C and bones as well, he says.
Vitamin C and Bones: Advice
The new research isn't a call to dose up with supplements, Tucker says. She believes in getting as much vitamin C as possible from fruits and vegetables, supplementing with a vitamin tablet if necessary.
Getting enough vitamin D and calcium is also still important for bone maintenance, she says.
Heaney agrees and adds this advice: "Eat a good diet. Exercise, walk, skip rope, jog.''