If you enjoy reading health news, you may have heard that drinking a glass of citrus juice each day helps prevent kidney stones. This does, indeed, seem to be the case, but orange juice is much more effective than other citrus choices, according to new research from the University of Texas Southwestern Medical Center in Dallas.

Kidney stones develop when urine becomes too concentrated, causing minerals and other chemicals to bind together. Over time, these crystals combine and form a stone.

If you’ve ever suffered from painful kidney stones, your doctor has undoubtedly recommended dietary and lifestyle changes, including a prescription for potassium citrate, which makes urine less acidic. Some people, however, simply cannot tolerate the drug because of its gastrointestinal side effects, notes Clarita Odvina, MD, an assistant professor of internal medicine and the study’s lead author. In these cases, dietary sources of citrate, such as orange juice, may be an effective alternative to drugs.

All citrus juices contain citrate, a form of citric acid that gives citrus fruits their sour taste. But when researchers compared orange juice and lemonade, which have comparable citrate contents, they found orange juice boosted the levels of citrate in the urine and reduced the crystallization of uric acid and calcium oxalate (the “main ingredient” in kidney stones). Lemonade failed to increase levels of citrate—an important acid neutralizer and inhibitor of kidney stone formation.

If you’re a biochemistry geek, here’s how it works: The citrate in orange and grapefruit juice is accompanied by a potassium ion. The citrate in lemonade and cranberry juice is accompanied by a hydrogen ion. Hydrogen ions—but not potassium ions—counteract the beneficial effects of high citrate content.

So, the next time you head to your local natural and organic food store, grab a carton of freshly squeezed organic orange juice—or juice some organic oranges. Your kidneys will thank you!