Soy milk, soy cheese, soy burgers, tofu--you've probably heard about how good soy is for your body. It's high in protein, fiber and healthy oils; among other benefits, it reduces one's risk of cardiovascular disease. However, you may not have heard that soy can cause kidney stones.
You see, soy contains a compound called oxalate. Oxalate has no nutritional value, and our bodies cannot metabolize it; therefore, it must be excreted through the urine. This is potentially dangerous because oxalate can bind with calcium, forming kidney stones. These kidney stones, which can range from the size of a grain of rice to the width of a golf ball, can block the urinary system. The good news is that if you have a low risk for developing kidney stones in the first place, then you're unlikely to be affected by the oxalate in soy.
However, high levels of oxalate in the urine do increase your risk of kidney stones. And if you have a history of kidney stones, some researchers say you shouldn't consume a morsel of soy. The amount of oxalate in most soy products is much higher than what the American Dietetic Association recommends for patients with kidney stones. In fact, the amount of oxalate in some of these products, like textured soy protein, is as much as fifty times higher than the recommended serving. Other foods, like spinach, are also extremely high in oxalate.
Further research needs to be done to find soybeans with lower amounts of oxalate or to develop a process that will take the oxalate out before the soy hits the shelves.