Examination of the role of dietary nutrients in kidney stone formation using a novel “relative analogy model”

In South Africa, kidney stones are rare in Black individuals (B) compared to White individuals (W). We aimed to use this anomaly to evaluate the roles of various nutrients in stone formation and to explore possible explanations for the disparity. A literature review identified 24 nutrients with statistical associations to stone formation (conventional model, CONVM). These were compared to findings from an innovative model in which nutrient intakes in healthy B (n = 51) and W (n = 51) were considered analogous to those in non-stone formers and stone formers, respectively (relative analogy model, RAM). RAM data were retrieved from our nutrient records, compiled during previous studies. These data were analysed using hypothesis testing and logistic ridge regression. Using RAM we designated a nutrient as promotive if intake in W > B, and protective if intake in B > W (p < .05). Five nutrients were deemed promotive by both models (energy, animal protein, total sugar, added sugar, Na). Four nutrients showed conflicting results (Ca, Mg, K, citric acid). Six were promotive by RAM but inconclusive by CONVM (moisture, total protein, total fat, P, vitamin A, vitamin B6). Two were protective by CONVM but inconclusive by RAM (fibre, vitamin C). Seven were inconclusive in both models (carbohydrate, Cl, vitamin D, vitamin E, phytate, oxalic acid, arachidonic acid). We propose that kidney stones result from imbalances between promotive and protective nutrient intakes and that the lower stone incidence in B is due to reduced intake of promotive nutrients, rather than increased intake of protective ones.