The composition of urine is influenced by diet and changes in dietary factors have been proposed to modify the risk of recurrent
nephrolithiasis. Nutrients that have been implicated include
calcium, oxalate,
sodium, animal
protein,
magnesium and
potassium. There is significant evidence showing that a high
calcium diet is associated with a reduction of lithogenic risk. One of the possible mechanisms to explain this apparent paradox is that the higher intake of
calcium in the intestine binds with dietary
oxalate, reducing its absorption and urinary excretion.
Oxalate from the diet seems to provide only a small contribution to excretion and
dietary restriction is appropriate only in those with
hyperoxaluria and hyperabsorption. Observational studies have shown a positive and independent association between
sodium intake and the formation of new
kidney stones. Consumption of animal
protein creates an
acid load that increases urinary excretion of
calcium and
uric acid and reduced
citrate, all factors that could participate in the genesis of stones.
Potassium-rich foods increase urinary
citrate because of its
alkali content. In prospective observational studies, diets rich in
magnesium were associated with a lower risk of
kidney stone formation in men. In conclusion, diet is a key
element in the management of the patient with
kidney stones but always subordinated to present metabolic risk factors.