Some doctors are telling their patients that vitamin D causes kidney stones. It makes sense right? Vitamin D is involved with calcium absorption so that calcium may increase the risk for kidney stones. The theory has what we call “face validity,” which means it sounds right.
However, two recent studies have found just the opposite; the lower your 25(OH)D, the higher the risk for kidney stones.
In January of 2016, Dr. Ticinesi and colleagues studied 884 subjects with kidney stones and 967 controls. They found that the prevalence of vitamin D deficiency (< 20 ng/ml) was 56% in stone formers and 44% in controls (P <.001), with median vitamin D levels of 18 ng/mL versus 23 ng/mL. After a fully adjusted analysis, those with vitamin D deficiency were more than twice as likely to develop a kidney stone.
In April of 2016, Dr. Girón-Prieto and colleagues did a case control study of 366 subjects, 239 of which had a history of kidney stones. They also found that those with low 25(OH)D levels were more likely to develop kidney stones.
This goes to show that face validity (sounds right) can be wrong, sometimes with significant consequences. The cholesterol/fat theory of heart disease had face validity, so we started eating low cholesterol/fat diets. However, such diets did not reduce heart attacks; instead, they contributed to the obesity epidemic.
It just goes to show why one has to be careful of assumptions. Vitamin D may sound like it will cause kidney stones, but the opposite is actually true.