A systematic review published in Annals of Internal Medicine in 2026 pooled 31 studies and found that, for adults with calcium stones, a diet with normal to high calcium, low protein and low sodium was among the approaches that may reduce recurrence. A 2024 umbrella review reached a similar conclusion: dietary calcium and calcium supplements made no difference to stone risk, or reduced it. Neither review supports cutting calcium back.
Why almost everyone assumes the opposite
The logic feels airtight. The stone was made of calcium oxalate. Calcium is in the stone. Eat less calcium.
Nearly everyone reaches this on their own, and some are told it outright.
What the reviews actually found
The 2026 systematic review searched trial registries and databases through December 2025 and included 31 studies — 26 of them randomised controlled trials. For adults with calcium oxalate or calcium phosphate stones, the interventions that may reduce recurrence were:
- increased water intake
- a diet with normal to high calcium, low protein and low sodium
- thiazide diuretics
- alkali treatment
- allopurinol
Note where calcium sits in that list. It is not something to minimise; it appears as part of a dietary pattern associated with fewer recurrences.
The 2024 umbrella review, which assessed 17 meta-analyses covering 46 candidate risk factors, put it more bluntly. Its authors singled out calcium as a case where the common belief runs against the data: calcium supplementation, dietary calcium, and vitamin D — described as widely believed responsible for stone formation — made no difference or even reduced the risk.
The mechanism, briefly
Calcium and oxalate bind to each other. When they meet in the gut, they form a compound the body does not absorb, and it leaves in stool rather than reaching the kidneys.
Eat less calcium and less oxalate gets intercepted on the way through. More is absorbed, more reaches the urine, and urinary oxalate rises — and urinary oxalate is directly linked to calcium oxalate stone risk.
This is also why timing is discussed in the literature: calcium has to be present at the same time as the oxalate for the two to meet.
The honest caveat, which the reviews state themselves
Every one of those conclusions in the 2026 review was rated low strength of evidence.
That is the review's own assessment, not a criticism of it. It means the direction of the finding is supported but the confidence is limited — the trials are small, few, and heterogeneous. It is a considerable step up from the general run of stone-prevention advice, and it is still not certainty.
You should be suspicious of any page on this topic, including this one, that sounds more confident than that.
What this does not mean
It does not mean eating more calcium prevents stones. It does not mean calcium supplements are equivalent to calcium in food — the reviews assessed them separately, and the literature treats them differently, partly because of timing with meals.
And it does not override your own situation. High urinary calcium has medical causes that are managed on their own terms.
The one thing worth doing
If you have cut back on dairy or calcium since your stone, say so at your next appointment. It is an extremely common, well-intentioned change, the evidence does not support it, and your clinician cannot correct it if they do not know you have made it.
If you have had a 24-hour urine collection, your urinary calcium and oxalate values are what turn this from a general argument into your specific situation.