CHICAGO - Including more calcium in the diet may help to reduce the risk of kidney stone formation in younger women, according to an article in the April 26 issue of The Archives of Internal Medicine, one of the JAMA/Archives journals. According to information in the article, diet plays an important role in the development of kidney stones. In older men and women, higher levels of calcium, sodium, animal protein, and sucrose (sugar) may be associated with a higher risk of developing kidney stones, the article states. A compound called phytate (found in plants and cereal grains) may also play a role and might inhibit the formation of kidney stones by preventing tiny crystals of calcium oxalate (which is a component of kidney stones) from forming. Gary C. Curhan, M.D., Sc.D., of Brigham and Women's Hospital, Boston, and colleagues examined the association between diet and risk of developing kidney stones among 96,245 female participants aged 27 to 44 years in the Nurses' Health Study II. Participants had no history of kidney stones and completed questionnaires on types and quantities of foods they ate in 1991 and 1995.
The researchers documented 1,223 new kidney stones over the eight years of the study. They found that higher dietary calcium was associated with a reduced risk of kidney stones. Women who consumed the most calcium (top 20 percent of calcium intake) had a 27 percent lower risk of developing kidney stones compared to women who reported consuming the least amount of calcium (lowest 20 percent of calcium intake). Calcium supplement use was not associated with risk of kidney stone formation. The researchers found that phytate consumption was also associated with a reduced risk of stone formation. Women who consumed the most phytate (top 20 percent of phytate intake) in the study group had a 37 percent lower risk of developing kidney stones compared to women who consumed the least amount of phytate (lowest 20 percent of phytate intake).
"In summary, our findings indicate that a higher intake of dietary calcium decreases the risk of kidney stone formation in younger women," the authors write. "The lack of an increased risk with greater intake of calcium and the potential to increase the risk with calcium restriction reinforce that the routine restriction of dietary calcium in patients who have had a kidney stone is no longer justified."
"This study also suggests that some dietary risk factors may differ by age and sex. Finally, dietary phytate may be a new, important, and safe addition to our options for stone prevention."
Arch Intern Med. 2004;164:885-891. archinternmed.com. This study was supported by grants from the National Institutes of Health, Bethesda, Md.
