What is the role of hydration and dietary advice in kidney stone prevention?

• A. Adequate fluid intake to keep urine dilute; reduce salt and high-oxalate foods; maintain normal calcium intake; limit animal protein
• B. Decrease fluids to concentrate urine
• C. Increase salt and oxalate intake
• D. Avoid fluids entirely

Answer: (A)

Hydration and diet shape urine composition and stone risk. Keeping urine dilute by drinking plenty of fluids lowers the concentration of stone-forming minerals, making crystallization less likely and helping prevent stones from forming. Aim for enough fluid intake to produce a pale, clear urine volume that supports roughly 2 to 2.5 liters of urine a day, adjusting for climate and activity.

Dietary adjustments support this effect. Reducing sodium intake lowers urinary calcium excretion, which helps prevent calcium-containing stones. Limiting foods very high in oxalate can also reduce urinary oxalate, a common stone contributor, especially in people who form calcium oxalate stones. Maintaining normal calcium intake is important because dietary calcium binds oxalate in the gut, reducing its absorption; very low calcium can paradoxically raise stone risk. Limiting animal protein lowers acid load in the body, decreases urinary calcium and uric acid excretion, and preserves citrate, a natural stone inhibitor.

Other choices would concentrate urine or introduce more stone-promoting substances, increasing risk. The goal is to maximize urine volume while choosing foods that reduce the constituents that crystallize into stones and support natural inhibitors in the urine.