[Effect of cocoa on excretion of oxalate, citrate, magnesium and calcium in the urine of children].

Cocoa is a strong carrier of oxalic acid (average: 400 mg per 100 g). In three calcium oxalate stone formers clinical observation had been suggestive of excessive intake of cocoa products contributing to calculus formation. We studied the effect on renal oxalate excretion of an oral cocoa load (30 g per m2 body surface given on 2 consecutive days) in 12 former stone formers (group 1), 14 children with isolated microscopic haematuria (group 2), 13 healthy boys (group 3), and 12 healthy girls (group 4). A new enzymatic method was used to measure oxalic acid in cocoa products as well as in urine samples by a two step reaction: 1. Oxalate decarboxylase, 2. formiate dehydrogenase with photometry of NADH. In addition, the daily excretion of the following substances was measured: Citrate, magnesium, and calcium. There was a significant increase of urinary oxalate excretion from an average of 14.5 mg/24 hours before to an average of 22.2 mg/24 hours after the load in healthy children, and a similar increase in stone formers, but not in children with microscopic haematuria. The excretion of citrate and magnesium did not change following cocoa intake. The calcium excretion was higher in stone formers than in the other groups, but the difference was significant only compared to group 2. It is concluded that the risk of calculus formation may increase following continuous and excessive intake of cocoa products in children with a tendency toward hypercalciuria. Counselling of the stone formers resulted in a marked drop of the daily oxalate excretion, and there was no recurrence of calculus formation over a period of 6 years.(ABSTRACT TRUNCATED AT 250 WORDS)