Kidney stones form when certain chemicals become concentrated enough in the urine to form crystals. The crystals grow into larger masses (stones), which can make their way through the urinary tract. If the stone gets stuck somewhere and blocks the flow of urine, it causes pain.
Most stones occur when calcium combines with one of two substances: oxalate or phosphorous. Stones can also form from uric acid, which forms as the body metabolizes protein.
How to avoid kidney stones
Preventing kidney stones means preventing the conditions that support their formation. I asked Dr. Melanie Hoenig, an assistant professor of medicine at Harvard-affiliated Beth Israel Deaconess Medical Center, for the top ways to prevent kidney stones. Here are her recommendations:
Drink plenty of water
Get calcium you need
Limit animal protein
Avoid stone-forming foods like beets, chocolate, spinach, tea, and most nuts rich in oxalate, and colas are rich in phosphate, both of which can contribute to kidney stones.