We revealed that, in stone former men, a diet with a high DII is significantly related to the increased odds of having hypercreatininuria, hypercalciuria, hyperuricosuria, and hypocitraturia, but not to hyperoxaluria.
It has been confirmed that kidney stone formers could be susceptible to recurrence in stones formation because of unhealthy dietary patterns [32]. We previously [30] found that adherence to an unhealthy dietary pattern, which was high in high fat diaries, red meats, sweets-desserts, junk foods, coke-fizzy drinks, and fast foods, is significantly associated with hypercalciuria and hypocitraturia, but not with hyperoxaluria. Nevertheless, inconsistent with our finding, a study did not report any significant difference in creatinine across tertiles of DII in subjects with chronic kidney disease [33]. A randomized controlled trial study by Noori et al. [34] on recurrent stone formers showed that a DASH diet, which in contrast to a diet with a high DII, is featured by a high intake of whole grains, fruits, low-fat dairy products and vegetables, and a low intake of total fat, cholesterol, saturated fat, meat, and refined grains, is significantly associated with a decrease in calcium oxalate supersaturation and an increase in citrate excretion. Moreover, another study reported that greater adherence to the Mediterranean dietary pattern (characterized by high consumption of fruits and vegetables, fish, olive oil, nuts, and legumes; low consumption of saturated fats, meat, and sugars; and moderate consumption of wine, is related to the reduced risk for incident kidney stones [35]. The relationship between systemic inflammation and nephrolithiasis has been identified previously [13]. Since both DASH and Mediterranean diets attenuate inflammation [16 36], the protective effects of these dietary patterns on kidney stones formation may be mediated, at least partly, by reducing systemic inflammation. A cross-sectional conducted on diabetic patients also reported that higher intake of “vegetable and fish” dietary pattern is related to a lower creatinine rates [37]. Vegetables and fish, as components of DII, are identified to have anti-inflammatory effects [38 39]. The DII is a tool to assess the overall impact of a diet on inflammatory potential [29], and is associated with markers of systemic inflammation including such as IL-6 [24], and CRP [26] [..]; IL-6 and CRP are two of the inflammatory biomarkers considered in the calculation of DII [29]. It has been revealed that the DII score is inversely related to the Dietary Approaches to Stop Hypertension Score (DASH) (r = − 0.52, p < 0.01), Mediterranean Diet Score (r = − 0.45, p < 0.01), and Healthy Eating Index-2010 (r = − 0.65, p < 0.01) [40 41]. Taken together, these findings support that a likely mechanism for the relation of DII scores to hypercreatininuria, hypercalciuria, hyperuricosuria, and hypocitraturia could be explained by the higher systemic inflammation level among people following a pro-inflammatory diet.