The purpose of this study was to determine the effects of consumption of different cocoa-derived products on uric acid crystallization in urine of 20 healthy volunteers. Participants were requested to select the specific diet that they wished to follow during the 12 h prior to collection of urine. The only restriction was that the diet could not include any product with cocoa, coffee, or caffeine. On the first day, each volunteer followed their selected diet, and an overnight 12 h urine sample was collected as the baseline urine. After seven days on an unrestricted diet, each volunteer repeated the same diet with 20 g of milk chocolate, chocolate powder, or dark chocolate during breakfast and another 20 g during dinner. Overnight 12 h urine samples were then collected. Urine volume, pH, oxalate, creatinine, uric acid, theobromine, and a uric acid crystallization test were determined for each sample. The results for all 20 patients show that uric acid crystallization was significantly lower following the consumption of chocolate powder or dark chocolate relative to baseline or following the consumption of milk chocolate. The results indicated that increased concentrations of urinary theobromine reduced the risk of uric acid crystallization.

Myo-inositol hexaphosphate (phytate; IP6) is a natural compound that is abundant in cereals, legumes, and nuts, and it can bind to crystal surfaces and disturb crystal development, acting as crystallization inhibitor. The adsorption of such inhibitors to crystal faces can also inhibit crystal dissolution. The binding of phytate to metal cofactors suggests that it could be used for treatment of osteoporosis. Our in-vitro study showed that phytate inhibits dissolution of hydroxyapatite (HAP). The effect of phytate was similar to that of alendronate and greater than that of etidronate. This led us to perform a cross-sectional study to investigate the impact of consumption of IP6 on bone mineral density (BMD) in post-menopausal women. Our data indicate that BMD and t-score of lumbar spine increased with increasing phytate consumption, and a phytate consumption higher than 307 mg/day was associated with a normal BMD (t-score > −1). These data suggest that phytate may have a protective effect in bone decalcification by adsorbing on the surfaces of HAP, and a daily consumption of phytate-rich foods (at least one serving/day of legumes or nuts) may help to prevent or minimize bone-loss disorders, such as osteoporosis. However, further studies are needed to gain a better understanding about the mechanism of inhibition of phytate in bone-related diseases (see graphical abstract).

Background. Uric acid (UA) renal lithiasis has a high rate of recurrence and a prevalence ranging from 10% and 15%, depending on the population. The most important etiological factor is persistence of urinary pH below 5.5 and one of the most common treatments is alkalization with citrate. Recent studies demonstrated that theobromine, which is abundant in chocolate and cocoa, is a potent inhibitor of UA crystallization. Aim. The aim was to compare the efficacy of citrate versus citrate + theobromine as treatment for UA lithiasis. Methods. This randomized cross-over trial investigated the efficacy of two treatments in 47 patients with UA renal lithiasis. Urine volume, pH, UA excretion, theobromine excretion, and risk of UA crystallization (RUAC) at baseline and at the end of each intervention period were measured. Results. Each treatment significantly reduced the risk of UA crystallization compared to basal values. The RUAC after citrate + theobromine was lower than the RUAC after citrate, although this difference was not statistically significant. Conclusion. The combined consumption of citrate and theobromine may be a promising strategy for the prevention of UA kidney stones.