DASH-Style Diet Associates with Reduced Risk for Kidney Stones

The impact of the Dietary Approaches to Stop Hypertension (DASH) diet on kidney stone formation is unknown. We prospectively examined the relation between a DASH-style diet and incident kidney stones in the Health Professionals Follow-up Study (n = 45,821 men; 18 yr of follow-up), Nurses'' Health Study I (n = 94,108 older women; 18 yr of follow-up), and Nurses'' Health Study II (n = 101,837 younger women; 14 yr of follow-up). We constructed a DASH score based on eight components: high intake of fruits, vegetables, nuts and legumes, low-fat dairy products, and whole grains and low intake of sodium, sweetened beverages, and red and processed meats. We used Cox hazards regression to adjust for factors that included age, BMI, and fluid intake. Over a combined 50 yr of follow-up, we documented 5645 incident kidney stones. Participants with higher DASH scores had higher intakes of calcium, potassium, magnesium, oxalate, and vitamin C and had lower intakes of sodium. For participants in the highest compared with the lowest quintile of DASH score, the multivariate relative risks for kidney stones were 0.55 (95% CI, 0.46 to 0.65) for men, 0.58 (95% CI, 0.49 to 0.68) for older women, and 0.60 (95% CI, 0.52 to 0.70) for younger women. Higher DASH scores were associated with reduced risk even in participants with lower calcium intake. Exclusion of participants with hypertension did not change the results. In conclusion, consumption of a DASH-style diet is associated with a marked decrease in kidney stone risk.Diet plays a major role in the development of kidney stones, and dietary changes likely have contributed to the substantial increase in nephrolithiasis over the past several decades.^1,2 A wide variety of dietary factors either promote or inhibit the formation of calcium oxalate kidney stones,^1,2 the most common type of stone.³Despite previously observed associations between individual dietary factors and kidney stone risk,² relatively few studies have examined the impact of overall diet or dietary patterns on risk. The identification of an effective stone prevention diet is difficult partly because most diets are isocaloric: if an individual reduces the intake of certain foods, he or she will increase the intake of other foods to maintain constant energy intake.⁴ As a result, consuming less of one dietary factor (such as animal protein⁵) to decrease stone risk may lead to the consumption of other factors (such as sucrose or fructose⁶) that increase risk.The Dietary Approaches to Stop Hypertension (DASH) diet, which is high in fruits and vegetables, moderate in low-fat dairy products, and low in animal protein represents a novel potential means of kidney stone prevention. The consumption of fruits and vegetables increases urinary citrate,⁷ an important inhibitor of calcium stone formation, and a diet with normal to high calcium content but low in animal protein and sodium decreases the risk of calcium oxalate stone recurrence by 51%.⁸ The DASH diet also lowers BP,⁹ which is particularly appealing given the high rates of prevalent and incident hypertension in stone formers.^10–14 Because the DASH diet would be expected to contain higher amounts of oxalate and vitamin C, both of which may increase calcium kidney stone risk,^15,16 the impact of the DASH diet on stone risk is currently unknown.To examine the relation between a DASH-style diet and the risk of incident kidney stones, we conducted prospective studies in three large cohorts: the Health Professionals Follow-up Study (HPFS), the Nurses'' Health Study I (NHS I), and the Nurses'' Health Study II (NHS II). Previously, we identified associations between individual dietary factors and stone risk in each of these study populations.^5,6,15–18 For the first time, we now report the impact of a specific dietary pattern on risk.