In my line of work, summertime has an unfortunate characteristic: We see a lot more patients troubled by kidney stones.
A short primer on their cause: The kidneys are responsible for filtering body waste from the blood, and they turn waste into urine. Urine may look clear, but it actually contains small particles that can clump together, forming stones. If you have a little blood in your urine or a mild ache in your back below your ribs that comes and goes, it could be a kidney stone. (When a stone blocks the ureter—the duct that takes urine from the kidney to the bladder—that’s what causes severe pain, often resulting in an emergency room visit.)
Dehydration is the primary culprit, which is why we see an uptick of kidney stones in the summer. So the first line of defense is drinking water throughout the day—a half-gallon, plus more if you’re exercising, especially in the heat. Your urine should be almost clear, with just a touch of yellow. If it looks like a sports drink (yellow or orange), that’s a problem. And remember that caffeine, soda, and alcohol can ultimately make you dehydrated, so take that into account.
Kidney stones strike men more often in middle age, not because our kidneys slow down but because we pay less attention to what we’re drinking. If you have coffee in the morning, a diet soda at lunch, and wine with dinner, you’re setting yourself up for problems.
The secondary cause is diet. High protein intake, such as red meat, can increase the risk of kidney stones. So can excessive consumption of oxalate—an acid found in plants and fruits like spinach, blueberries, strawberries, kale, almonds, and black tea.
Obviously these are all healthy foods, and I’m not suggesting that you should avoid them. Rather than omitting them from your diet, offset oxalate by—you guessed it—drinking more water.
Benjamin Choi, M.D., is a urologist in New York City and a clinical assistant professor of urology at Weill Cornell Medicine.