The present study aims to assess the effectiveness of theobromine, -product present in high proportion in the cacao-, to prevent the development of uric acid kidney stones.

Renal lithiasis is a pathology that affects a high percentage of the population, and although it has been known for a long time, advances carried out in the treatment are limited to the surgical aspects, while the causes responsible for the formation of kidney calculus are not corrected, which leads to a high recurrence.

The "healing" of renal lithiasis inevitably goes through the elimination of the alterations related to the genesis of kidney calculus. It the case of uric acid lithiasis the most important are having urinary pH less than 5.5 and an elevated uricosuria, which can be corrected relatively easy by undergoing changes in dietary habits, and with pharmacological treatment with citrate -which produces and increase in pH- or with inhibitors of the xantino-oxidase as allopurinol. However, among the prophylactic treatments available for ural acid lithiasis, so far it does not exist one for urinary acid crystallization inhibition.

Recently, the effects of theobromine as an inhibitor of the crystallization of uric acid have been described, but only in vitro. The present study aims to assess the effectiveness of theobromine, -product present in high proportion in the cacao-, to prevent the development of uric acid kidney stones.

The study is a unicentric, low intervention, non-randomized, prospective study to assess the effects of the consumption of different cocoa derivate products, in the risk of crystallization of uric acid in the urine. Participants in the study are healthy volunteers and will it will be carried out with 20 individuals who will be recruited in the Research Laboratory in Renal Lithiasis of the Baleares Isles University.

Patients will take a urine test previously to undergo 4 dietary interventions, with their subsequent urine measurements. Patients will choose one diet to follow for 1 day, and will be provided with the corresponding cocoa derivate for the diet (soluble cocoa, black chocolate, chocolate with milk). The day after the diet they will take a fast-picking of urine accumulated during the night of which they followed the controlled diet (12 h nocturne sample), then follow a 6 day washout period, and select another diet to follow and repeat until they have gone through the 4 diets and measurements.

Inclusion Criteria:

• Compliance in participating and collaborating in the study

Exclusion Criteria:

• Cocoa / chocolate allergy or theobromine
• Pregnancy, nursing period (women)
• pharmacological treatment
• chronic diseases (diabetes, kidney failure, heart failure, hyperuricemia, ...)