If you’ve ever had kidney stones, you know one sure thing: They’re painful! And having one attack means there’s a good chance you’ll endure more. But there are reliable ways to avoid a reoccurrence—or to keep from getting kidney stones in the first place, says Dr. Fredric Coe, medical director of the Kidney Stone Prevention Program at the University of Chicago School of Medicine. Knowing what kind of stone you have is important; there are different prevention strategies for different types. If your doctor didn’t have your stones analyzed, urine and blood tests can help determine what caused your stones, and what you’ll need to do to prevent others, Coe says. For most kinds of stones, including the most common type, calcium oxalate, here’s what he recommends to reduce your risk.
Drink enough plain, filtered water so that you urinate every two to three hours during the time you are awake. “Your bladder should be full, so that you need to urinate, not just be able to urinate,” Coe says. Note to construction workers, athletes and anyone else active in hot weather: If you drink gallons but sweat even more, you are not protecting your kidneys. It’s urine output that counts.
Limit caffeine and alcohol. Even though they may initially increase urine output, both ultimately deplete your body of water. Plus, caffeine increases the amount of calcium in your urine.
Cut way back on salt. A high-salt diet makes you excrete calcium from your body, boosting your risk for both kidney stones and weak bones, Coe says. He recommends no more than 2,300mg of sodium a day–about 1,000mg less than many people consume. While fast foods, chips and processed meats are known culprits, bread and rolls, pizza, sodium-injected poultry, soups and cheese also have lots of sodium. Read labels: Avoid foods with more than 300 mg of sodium per serving.
Axe the oxalates. Oxalates are organic molecules found in many fruits and vegetables. In your kidneys, oxalates can bind with calcium to form an insoluble salt that can be the beginning of a kidney stone. Many foods contain oxalates, but Coe has found that for men, the high-oxalate foods most likely to cause trouble are chocolate, nuts and black pepper. For women, it’s leafy greens. Not all leafy greens contain oxalates, though. Spinach is high in oxalates; kale is low. “I tell people to find a list online, and see what oxalate foods they eat the most,” he says. Check this list for the oxalate content of common foods.
Add calcium. Eating a calcium-rich food with the oxalate food actually helps to prevent kidney stones–because the calcium and oxalate bind in your intestines and never reach your kidneys. So think creamed spinach or chocolate pudding. Aim for about 800 to 1,000mg of calcium a day, Coe recommends. Calcium supplements don’t work as well as calcium-rich foods, and cutting back on calcium-rich foods doesn’t reduce your risk for kidney stones, he says.
Can the cranberries. Cranberries are loaded with oxalates, so avoid cranberries of all forms if you’re prone to calcium oxalate stones, Coe recommends. Cranberry extract, often used to prevent recurrent urinary tract infections, is especially high in oxalates.
Curb your sweet tooth. A sugary diet raises urinary calcium and reduces urine volume at the same time, so it is a double whammy when it comes to kidney stones, Coe says. “A little sugar is OK, just don’t overdo.”