From the Guidelines
Dietary calcium restriction is not recommended for reducing urine calcium levels in patients with kidney stones, as it may actually increase the risk of stone formation by allowing more oxalate absorption in the intestines. Instead, a moderate calcium intake of about 1000-1200 mg per day is typically recommended, preferably from dietary sources rather than supplements, as evidenced by a 5-year randomized controlled clinical trial that showed a 51% lower risk of developing a recurrent stone on a normal calcium diet compared to a low-calcium diet 1. This approach helps bind oxalate in the intestines, preventing its absorption and subsequent excretion in urine, thereby reducing the risk of kidney stone formation. For patients with calcium-based kidney stones, other dietary modifications are more beneficial, including:
- Increased fluid intake (2-3 liters per day) to achieve a urine volume of at least 2.5 liters daily, as recommended by the AUA guideline 1
- Reduced sodium intake (less than 2300 mg daily) to limit urinary calcium excretion, as supported by prospective observational studies 1
- Limited animal protein consumption to reduce urinary calcium and uric acid excretion, as suggested by the study on diet and fluid prescription in stone disease 1
- Normal calcium intake with meals to help bind oxalate in the intestines and prevent its absorption. These approaches, rather than calcium restriction, are more effective at reducing stone risk while maintaining bone health, as severe calcium restriction can lead to negative calcium balance and bone demineralization over time.
From the Research
Dietary Calcium Restriction and Urine Calcium Excretion
- Dietary calcium restriction can reduce urinary excretion of calcium, but it may also increase urinary oxalate excretion, which can contribute to the formation of calcium oxalate kidney stones 2, 3.
- Severe dietary restriction of calcium can cause hyperoxaluria and a progressive loss of bone mineral component 3.
- A diet with adequate calcium intake (1000-1200 mg/day) and moderate restriction of animal protein and salt can decrease urinary supersaturation for calcium oxalate and reduce the relative risk of stone recurrence in hypercalciuric renal stone formers 3.
- The relationship between urinary calcium and bone mineral density in patients with calcium nephrolithiasis is complex, and dietary calcium restriction is not recommended for stone formers with nephrolithiasis 4, 5.
Recommendations for Dietary Calcium Intake
- A calcium intake of 800-1200 mg/day is recommended for adults to reduce the risk of kidney stone formation 2, 3, 5.
- Dietary calcium restriction is not recommended for children with nephrolithiasis, and a balanced consumption of fruit and vegetables is advised 5.
- In older patients, a diet rich in calcium (1200 mg/day) is useful to maintain skeletal wellness and prevent kidney stones, but an higher supplementation could involve an increase of risk for both the formation of kidney stones and cardiovascular diseases 5.