The Role of Fluid Intake in the Prevention of Kidney Stone Disease

A systematic review of studies found that producing less than 900 mL of urine per day increases the risk of kidney stones, with a minimum safe urine output of 1.6 liters per day for those who've had stones before. The most effective beverages for prevention include low-calcium water, citrus juices, and blackcurrant juice, while cranberry and plum juices have less favorable effects. Drinking an additional 1.3 liters of fluid daily can help achieve protective urine levels and reduce kidney stone risk.

Kidney stones are becoming more common worldwide, and they often come back - about half of people who get kidney stones will have another episode within 5 years. But could something as simple as drinking more fluids help prevent them? A recent systematic review of scientific studies provides some clear answers.

Researchers analyzed 9 carefully controlled studies with 541 total participants, published over the last two decades. They specifically looked at studies where participants followed standardized diets while testing different beverages, allowing researchers to isolate the effects of various drinks on kidney stone risk.

Key Findings About Urine Output and Stone Risk

The research confirms that how much you pee really matters when it comes to kidney stone prevention. Here are the key numbers:

• If you produce less than 900 mL (about 3.8 cups) of urine per day, you're at higher risk for developing kidney stones even if you're otherwise healthy
• For people who've had kidney stones before, the minimum safe urine output is higher - at least 1.6 liters (about 6.8 cups) per day
• To achieve these protective urine levels, researchers recommend drinking an extra 1.3 liters (about 5.5 cups) of fluid daily on top of your normal intake

What Types of Drinks Help Most?

The studies tested many different beverages. Here's what worked best for preventing kidney stones:

• Water low in calcium was more protective than calcium-rich mineral water
• Citrus juices like orange, grapefruit, and apple juice helped reduce stone formation
• Blackcurrant juice showed benefits by making urine less acidic

Some beverages had mixed or potentially negative effects:

• Cranberry juice increased some risk factors for stones by making urine more acidic
• Plum juice had no significant effect either way

The evidence clearly shows that drinking more fluids - especially water low in calcium and citrus juices - can help prevent kidney stones. The key is drinking enough to produce at least 2-2.5 liters of urine per day. For most people, this means adding about 1.3 liters of extra fluid to their normal daily intake.