How can I prevent kidney stones?

The following dietary guidelines may help to prevent stone formation in people who are susceptible:^[1]

Drink lots of water, frequently: According to the National Kidney Foundation, one of the best strategies to avoid kidney stones is to drink lots of water on a daily basis.^[2] The formation of kidney stones is partially a function of the concentration of stone-forming substances in the urine. Frequent water intake will make the urine more diluted, preventing the buildup of stone-forming substances.^[3] People who are prone to getting kidney stones should aim to drink more than 2 liters of water per day (more during the summer, to account for increased water loss through sweating).^[3][1]

Note, however, that aggressive hydration, or drinking large volumes of water to “make a kidney stone pass faster,” is not supported by the evidence and will only make more urine, which will in turn cause more pain as the urine attempts to pass the kidney stone. Hydration is important in the prevention of kidney stones, but once someone has renal colic, overhydration does not help.^[4]

Limit high-oxalate foods: Since so many foods contain oxalate, a ‘low-oxalate diet’ may be difficult to achieve. Instead, foods that are high in oxalate should be limited. Some examples of foods with high oxalate content include spinach, beets, peanuts, chocolate, sweet potatoes, and wheat bran. In situations where high- oxalate foods can’t be avoided, there may be a benefit to consuming food high in calcium at the same time, which could limit oxalate absorption.^[5]

Consume calcium-rich foods: This one is counterintuitive—since most kidney stones consist of calcium oxalate, it would seem that limiting calcium intake would be beneficial. However, calcium has the opposite effect. The binding of calcium ions to oxalate in the stomach and intestines rather than the kidneys makes it less likely for stones to form. When calcium binds to oxalate in the gastrointestinal tract, the low-solubility calcium oxalate salt is mostly excreted in the stool. In contrast, low-calcium intake increases the absorption of oxalate molecules through the intestines and excretion via the urine. When oxalate levels increase in the urine, it is available to interact with calcium ions, where it forms calcium-oxalate kidney stones in the urinary tract.^[6]

Reduce sodium intake: Consuming extra sodium increases calcium leakage into the urine, promoting conditions for stone formation.^[7] It’s unclear exactly what sodium intake is ideal, but reducing sodium intake reduces urinary calcium levels, in turn reducing kidney stone risk.^[8]. A common recommendation is to aim for less than 2 g of sodium per day, which is equivalent to 5 g of table salt.^[1]

Avoid soda and other sugar-sweetened beverages: Consuming one or more sugar-sweetened sodas per day was associated with a 23-33% increase in risk of kidney stone formation compared to less than one serving per week.^[9] The connection between soda intake and kidney stones has been confirmed in a randomized controlled trial, which found that habitual soda-drinkers had reduced risk of recurring kidney stones after eliminating their intake of all soft drinks.^[10]

Limit animal protein consumption: Consumption of animal proteins can increase the amount of stone-forming substances such as calcium and uric acid in the urine, which could promote stone formation in people who are prone to getting kidney stones.^[11] Current guidelines from the American Urological Association recommend that people who are prone to getting kidney stones should limit their intake of animal proteins.^[5]