Influence of various beverages on urine acid output.

High dose methotrexate therapy requires a high alkaline urine output. In order to evaluate the effect of various beverages on the urine acid output, healthy volunteers (n = 6) took 1.5-2 liters of a test drink during a 2-h period. On the test day urine pH and urine acid excretion (titratable acid plus ammonia minus bicarbonate) were measured. Controls received water and tea as test drink. Orange juice (pH 3.64) and tube feeding (pH 6.78) both led to alkaline urine pH and significantly decreased urine acid output compared to the control group (n = 4, P less than 0.01 and n = 3, P less than 0.001, respectively). Yoghurt (pH 4.1), buttermilk (pH 4.58), and Coca-Cola (pH 2.54), on the other hand, all induced a higher acid output than the control group (n = 6) and a urine pH less than 7.0 during the whole test day (n = 6, NS; n = 6, P less than 0.02; n = 4, P less than 0.05, respectively). If high urine output with an alkaline pH is required, fruit juices or well balanced tube feeding, both with low cation and low sulfur-bound amino acid content, can accomplish this. Drinks with high inorganic acid content (such as Coca-Cola) or high sulfur-bound amino acid content such as yoghurt and buttermilk will result in acidification of the urine.