泌尿道結石以草酸鈣最多，所以預防草酵鈣結石的發生，飲食的控制也很重要。而茶葉含有極豐富的草酸，因此我們分析二種市售茶飲料品牌的草酸含量( A組），及測量五種普遍市售的茶葉經沖泡後的草酸濃度。茶葉的沖泡法分二種。一種以6克茶葉及140ml 100°C 的蒸餾水各模仿傳統沖泡法，各沖3泡，每泡各浸l分鐘後測量茶液的草酸濃度（B組），一種以6 克茶葉及140 ml 100°C的蒸餾水各浸泡5、10、15分鐘後測量（C組），結果顯示A組統一及開喜烏龍茶各含平均14.4 mg / L，及35.2 mg / L的草酸；B組各平均草酸濃度是烏龍茶第一泡為43.0 mg / L，金萱67.4 mg / L，鐵觀音55.2 mg / L，綠茶86.1 mg / L，紅茶76.9 mg / L；C組各15分鐘的平均草酸濃度是烏龍茶208.0 mg / L，金萱158 .l mg / L，鐵觀音100.4 mg / L，綠茶267.1 mg / L，紅茶38 .l mg / L。令人驚訝的是B、C組的自來水（蒸餾水的對照組）各平均草酸濃度是15.9 mg / L，及20.9 mg / L。以上的結果顯示茶葉中含有多量的草酸，而且浸泡越久草酸溶出越多，為減少草酸對結石生成的影響，應儘量減少草酸的攝食量，以避免結石的再生。

Calcium oxalate is a major component of renal stones, and oxalate is a substance found in abundance in many vegetables and teas. In this study, we undertook an investigation into the oxalate content of Taiwanese teas. Two commercial brands of tea available on the market (group A) and 5 types of tea leaves (groups B and C) were analyzed quantitatively for oxalate contents. In group B, 6 g of each type of tea leaves was soaked in 140 ml of distilled water at a temperature of 100 °C 3 times for 1 mm each, according to the traditional Taiwanese method of steeping tea. In group C, each type of tea leaf was soaked in the same manner as for group B, but for periods of 5, 10 and 15 mm. In commercial brands of tea drinks sold on the market (group A), average oxalate levels were 14.4 mg/L in the President brand and 35.2 mg/L in the Kai-She brand. In group B, the average oxalate contents of the solutions after the first soaking were 43.0 mg/L in oolong tea, 67.4 mg/L in jinghsuan tea, 55.2 mg/L in tiehguanying tea, 86.1 mg/L in green tea, and 76.9 mg/L in black tea. In group C, the average oxalate contents of the solution after 15mm of soaking were 208.0 mg/L in oolong tea, 158.1 mg/L in jinghsuan tea, 100.4 mg/L in tiehguanying tea, 267.l mg/L in green tea, and 38.l mg/L in black tea. It is also interesting to note that tap water, in contrast to much lower levels in distilled water, contained average oxalate levels of 15.9 mg/L and 20.9 mg/L respectively in groups B and C. Based on the aforementioned observations, it is apparent that the 5 types of tea leaves analyzed are all characterized by significant oxalate levels. The longer the tea leaves are soaked, the more oxalate that is released.