Kidney stones affect between 8% and 12% of the population, and the most common, accounting for up to 80% of cases, are calcium oxalate stones. *1 Oxalate is a compound found in various foods such as spinach, rhubarb, cocoa, and beets, and can bind to calcium to form insoluble crystals that, under certain conditions, accumulate in the kidneys 1.
Because 20% to 40% of kidney stone cases2 are associated with excess calcium in the urine (hypercalciuria), it was thought for years that consuming calcium supplements could increase the risk of stone formation.
However, recent scientific evidence shows that restricting dietary calcium intake can increase, not decrease, the risk of developing kidney stones. This is because dietary calcium binds to oxalate in the intestine, reducing its absorption and subsequent urinary excretion, which in turn reduces the formation of calcium oxalate stones. 3
The Nurses' Health Study, which included 91,731 women followed for 12 years, observed that those with higher dietary calcium intake had a significantly lower risk of developing kidney stones compared to those with lower intake. 4
Another study involving more than 45,000 men found that a calcium intake of less than 850 mg per day was associated with a higher incidence of symptomatic kidney stones, while those who consumed more calcium (mainly through food) had a lower risk. 5
This supports the idea that calcium, far from being an enemy, can have a protective effect in individuals susceptible to kidney stone formation.
We can conclude that despite popular beliefs, scientific evidence indicates that adequate calcium intake, even through supplements, not only does not increase the risk of kidney stones but can help prevent them, especially when taken in the context of a balanced diet and accompanied by the right nutrients.
If you have a history of kidney stones or are considering taking a calcium supplement, it is best to consult with a healthcare professional to determine the best nutritional strategy and supplementation based on your individual profile.
References:
*1 Wang, K., Ge, J., Han, W., Wang, D., Zhao, Y., Shen, Y., Chen, J., Chen, D., Wu, J., Shen, N., Zhu, S., Xue, B., & Xu, X. (2022). Risk factors for kidney stone disease recurrence: A comprehensive meta-analysis. BMC Urology, 22(1), 62. https://doi.org/10.1186/s12894-022-01017-4
*2 Coe, F., Worcester, E., & Evan, A. (2016). Idiopathic hypercalciuria and formation of calcium renal stones. Nature Reviews Nephrology, 12, 519-533. https://doi.org/10.1038/nrneph.2016.101.
*3 Curhan, G., Willett, W., Rimm, E., & Stampfer, M. (1993). A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones.. The New England journal of medicine, 328 12, 833-8 . https://doi.org/10.1056/NEJM199303253281203.
*4 Curhan, G., Willett, W., Speizer, F., Spiegelman, D., & Stampfer, M. (1997). Comparison of Dietary Calcium with Supplemental Calcium and Other Nutrients as Factors Affecting the Risk for Kidney Stones in Women. Annals of Internal Medicine, 126, 497-504. https://doi.org/10.7326/0003-4819-126-7-199704010-00001.
*5 Curhan, G., Willett, W., Rimm, E., & Stampfer, M. (1993). A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones.. The New England journal of medicine, 328 12, 833-8 . https://doi.org/10.1056/NEJM199303253281203.
