Tschöpe W, Ritz E
Miner Electrolyte Metab. 1985;11(3):137-9.
Epidemiological evidence suggests a relation between dietary protein intake and nephrolithiasis. In addition, generation of acid equivalents from dietary protein increases urinary calcium excretion. To further evaluate the usefulness of epidemiological or clinical tools to study the relation between dietary protein and urinary calcium, the correlation between urinary urea and sulfate excretion on the one hand and calcium excretion on the other hand was examined in 42 healthy individuals. Only a modest correlation was found between urea and calcium excretion (r = 0.33); in contrast, the correlation between sulfate and calcium excretion was marked (r = 0.73) and highly significant (p less than 0.01). It remained significant when the influences of urea, sodium, hydroxyproline, and oxalate excretion were taken into account using partial regression analysis. In 9 healthy male probands, addition of 6 g L-methionine (40 mmol) to their usual diet caused an increase of urinary sulfate (+ 3,795 mg/24 h) and urinary calcium (+ 86.4 mg/24 h). The variable methionine/cysteine-cystine content of dietary proteins may explain why urinary calcium is correlated better with urinary sulfate than urinary urea.
流行病学证据表明膳食蛋白质摄入量与肾结石之间存在关联。此外，膳食蛋白质产生的酸当量会增加尿钙排泄。为了进一步评估流行病学或临床工具在研究膳食蛋白质与尿钙关系方面的实用性，对42名健康个体的尿尿素和硫酸盐排泄量与钙排泄量之间的相关性进行了研究。结果发现尿素与钙排泄之间仅有适度的相关性（r = 0.33）；相比之下，硫酸盐与钙排泄之间的相关性显著（r = 0.73）且高度显著（p小于0.01）。使用偏回归分析考虑尿素、钠、羟脯氨酸和草酸盐排泄的影响后，该相关性仍然显著。在9名健康男性受试者中，在其日常饮食中添加6 g L-蛋氨酸（40 mmol）会导致尿硫酸盐（+ 3,795 mg/24 h）和尿钙（+ 86.4 mg/24 h）增加。膳食蛋白质中可变的蛋氨酸/半胱氨酸-胱氨酸含量可能解释了为什么尿钙与尿硫酸盐的相关性比与尿尿素的相关性更好。
