Higher dietary calcium intake from either dairy or non-dairy sources is independently associated with a decreased risk of symptomatic kidney stones, according to a new study.
This inverse association is independent of age, dietary factors, body size, and other kidney stone risk factors.
The study, by Eric N. Taylor, MD, MSc, and Gary C. Curhan, MD, ScD, both of Harvard Medical School in Boston, documented 5,270 incident kidney stones among men in the prospective Health Professionals Follow-up Study (HPFS) and women in the prospective Nurses’ Health Study (NHS) I and II. For the latest analysis, the researchers excluded men aged 60 years and older because they previously documented inverse associations between calcium intake and kidney stone risk in men younger than 60.
Compared with highest quintile with the lowest quintile of non-dairy calcium intake, the study showed that men in the HFPS and women in the NHS I and NHS II had a 29%, 19%, and 26% decreased risk of kidney stones, respectively, after adjusting for multiple variables, Drs. Taylor and Curhan reported online ahead of print in The Journal of Urology.
Comparing the highest with the lowest quintiles of dairy calcium intake, the risk of kidney stones was decreased significantly by 23%, 17%, and 24%, respectively.
“Restriction of dietary calcium should not be recommended as a means of calcium kidney stone prevention,” the researchers concluded.
The investigators explained that as a result of the high correlation between total dietary calcium and dairy intake in Western populations, previous large-scale observational studies of dietary calcium and kidney stone risk represent de facto studies of milk products and stone risk. “The data from our current study allows us to dismiss the important possibility that dairy products were solely responsible for previously observed associations between higher dietary calcium and lower risk of incident kidney stones,” they wrote.
They noted that their findings do not provide insight into why dietary calcium may have different effects on kidney stone risk than supplemental calcium, which in previous studies has been shown to be associated with a nominal increased in kidney stone risk.