To minimize the risk of kidney stones:
Limit or manage the intake of foods high in oxalate. Oxalate is more readily absorbed after gastric bypass surgery and later has to be excreted in the urine. Many foods contain small amounts of oxalate and it is impossible to avoid oxalate altogether. It does make sense to limit your intake of foods that contain a high concentration of oxalate. Another option is to manage the absorption of high oxalate foods by pairing them with calcium-rich foods. This will cause the oxalate to bind with the calcium in the intestine, preventing absorption. Food high in oxalate include black tea, nuts, dark leafy greens, rhubarb, beets, chocolate, sweet potatoes, cranberries, soy products, potato chips, French fries, bran, fiber-containing cereals and chocolate.