Development of a rapid food screener to assess the potential renal acid load of diet in renal stone formers (LAKE score).

AIM OF THE STUDY: The potential renal acid load of foods (PRAL) has been proposed as a causative factor of renal stone format ion in patients with calcium stones. Evaluation of the dietary PRAL seems to be advisable to evaluate the lithogenic potential of the diet of the individual patient.
MATERIALS AND METHODS: On the basis of a dietary questionnaire administered to a sample of 75 renal stone formers living in the urban area of Milan (Northern Italy), we selected the most frequently reported foods for each of 11 categories: grains, meats, cured meats, eggs, cheeses, legumes, potatoes, vegetables, fruit and juices, milk and dairies and bread. The PRAL per 100 g of each food was calculated considering its mineral and protein composition, the mean intestinal absorption rate for each nutrient and the metabolism of sulfur-containing amino acids. The PRAL/100 g of each main food category was then calculated considering the frequency of the most represented (up to six) foods in the respective food group and the PRAL/100 g of each food. Subsequently the PRAL/100 g value for each main food category was adjusted for the standard serving size. Finally, according to the value of the adjusted PRAL value a score was assigned to each group of foods and named as LAKE (Load of Acid to Kidney Evaluation) score.
RESULTS: The scores computed for grains, meats, cured meats, eggs, cheeses, legumes,potatoes, vegetables, fruit & juices, milk & dairies and bread were +2, +10, +6, +4, +10, -2, -10, -10, -10, +1 and +1, respectively. Two report forms were designed to allow a rapid collection of data about the intake of each food group. Time requested for filling the forms and to compute scores ranges from 2 to 4 minutes (report forms can be requested to a.trinchieri@ospedale.lecco.it).
CONCLUSION: LAKE score can be an useful and simple tool in order to evaluate the dietary PRAL and to suggest modifications to achieve its reduction for the prevention of calcium nephrolithiasis and other diseases.