Dietary and Lifestyle Considerations
Increase Fluid Intake
Fluid intake is ordinarily the most influential factor in determining urine volume and thus kidney stone risk (Curhan 2012), and drinking adequate volumes of fluids may be the most effective intervention for people with any type of kidney stone (UMMC 2013). Most individuals who have had a kidney stone should drink at least 2 L of water per day (Arrabal-Polo, Arrabal-Martin 2013; Aliotta 2015). In a study in 199 people monitored for five years following a kidney stone episode, subjects who increased their fluid intake enough to maintain a urine volume of 2 L or more per day had less than half the risk of recurrence compared with those who did not (Borghi 1996).
Citrus juices. Lemon and orange juice are good sources of citrate, help alkalinize the urine, and appear to protect against kidney stones (UMMC 2013; Kang 2007; Haleblian 2008; Trinchieri 2002; Ferraro 2013).
Drinking lemon juice increases the amount of citrate in urine and may prevent kidney stones (UMMC 2013). A preliminary study found that daily consumption of a mixture of 2 L of water, 4 ounces of reconstituted lemon juice, and an artificial sweetener increased urine citrate concentrations and reduced stone formation in people with hypocitraturia-related kidney stones (Kang 2007).
Orange juice appears to be protective as well: in an analysis of three large studies, people who drank the most orange juice were found to be 12% less likely to develop kidney stones than those who drank the least (Ferraro 2013).
Mineral water. Mineral water combines several properties with known efficacy for preventing kidney stone disease and stone recurrence. Water dilutes urine, the minerals calcium and magnesium help bind dietary oxalate and reduce calcium oxalate crystallization, and the carbonate in mineral water alkalinizes urine and provides substrate for citrate formation (Siener 2004; Rodgers 1997; Rodgers 1998; Trinchieri 1999; Karagulle 2007).
Although several studies have demonstrated a benefit of mineral water for stone formers, further controlled studies that more clearly establish this benefit, especially compared to tap water or other beverages, are needed.
Eat More Fruits and Vegetables
Fruits and vegetables exert protective effects against most types of kidney stones. They generally have a high water content, which increases urine volume, have an alkalizing effect on urine, increase urinary citrate, and are naturally low in sodium and rich in potassium and magnesium. Fruits and vegetables are also high in compounds called phytates, which inhibit calcium crystal formation in the urine and are associated with a lower stone risk (Sorensen 2014; Curhan 2004; Borghi 2006).
In a study in almost 84 000 postmenopausal women, intake of fiber, fruits, and vegetables were each associated with lower risk of first-time kidney stone episodes. Comparing women with the highest to those with the lowest intakes, fiber was associated with up to a 26% risk reduction, fruits up to a 25% reduction, and vegetables up to a 22% reduction (Sorensen 2014).
Reduce Sodium Intake
Sodium increases the amount of calcium in the urine (Friedlander 2015), and high sodium intake has been correlated with increased kidney stone risk (Sorensen, Kahn 2012). In one trial, individuals with calcium kidney stone disease and high urine calcium concentrations were instructed to increase their fluid intake to 2–3 L per day. They were then randomly assigned to either a low-sodium diet group or a normal diet. After three months, those on the restricted sodium diet had lower urine calcium and oxalate concentrations than people in the normal diet group (Nouvenne 2010). Sodium restriction may also be useful for preventing recurrence of cystine stones, since lower amounts of sodium in the urine are associated with lower urine cystine concentrations (Heilberg 2013).
Reduce Sugar Intake
Several studies suggest higher consumption of refined sugar, particularly fructose and sugar-sweetened sodas, increases urine and serum uric acid levels and kidney stone risk (Ferraro 2013; Bantle 2009; Curhan 2004; Friedlander 2015; Taylor 2008).
The effects of soda and other beverages on kidney stone risk were evaluated in an analysis of three large studies that together included over 194 000 people. The authors found that drinking sugar-sweetened beverages increased stone risk: drinking one or more sugary colas per day was associated with a 23% higher risk of kidney stones compared to drinking less than one per week, while daily consumption of non-cola sugar-sweetened drinks was associated with a 33% higher risk (Ferraro 2013).
Consume Adequate Dietary Calcium
It used to be believed that calcium from diet and supplements increased kidney stone risk, and conventional physicians even advised kidney stone patients to reduce calcium consumption. However, a rigorous review of 10 studies found calcium supplementation does not increase stone risk (Candelas 2012), and low calcium intake has now been linked to increased kidney stone risk (Martini 2002). For a more detailed discussion of calcium and kidney stones, see the “Integrative Interventions” section.
Reduce Dietary Purine Intake
Purines (nitrogenous organic compounds that form part of the chemical structure of DNA) can be metabolized into uric acid, which can increase the risk of uric acid and calcium oxalate stones. Uric acid comes from the breakdown of purines which are made in the body by normal metabolic processes, or may be present in the diet (Boza 2000; Yamaoka 1996; Ishikawa 2013). Foods highest in purines are organ meats and seafood, legumes, and brewers and baker’s yeast (UMMC 2013; PAMF 2010; Mayo Clinic 2015a). Eating a high-purine diet can increase both urine and blood uric acid levels (Kenny 2010). People with kidney stones related to high uric acid levels are typically advised to avoid purine-rich foods (UMMC 2013), but a low-animal protein or vegetarian diet that alkalinizes the urine is more important for preventing uric acid stone formation (Kenny 2010; Heilberg 2013; Kanbara 2010).
Reduce Dietary Oxalate Intake
While high urine oxalate concentrations increase risk of calcium oxalate stones, and a low-oxalate diet has traditionally been recommended for preventing recurrence of calcium oxalate kidney stones. Oxalate is present in many foods, and combines with calcium to for calcium oxalate stones (Xu 2013; Friedlander 2015; Assimos 2004).
Digestive diseases, including inflammatory bowel diseases, and bariatric weight loss surgery can result in increased absorption of oxalate from food, so stone formers with these histories may benefit from avoiding high-oxalate foods (Xu 2013; Nazzal 2015). Beets, okra, spinach, Swiss chard, French fries, sweet potatoes, nuts, tea, chocolate, and soy products are examples of oxalate-rich foods that may be eliminated or restricted on a low-oxalate diet (Mayo Clinic 2015b; Cleveland Clinic 2015). Adequate calcium intake may ameliorates risk of calcium oxalate stone formation by binding oxalate in the gut and preventing its absorption (Trinchieri 2013; Sorensen, Kahn 2012; Nazzal 2015).
The DASH Diet and Kidney Stones
The Dietary Approaches to Stop Hypertension (DASH) diet emphasizes fruits and vegetables, nuts, legumes, whole grains, and low-fat dairy products, and limits saturated fat, sodium, total fat, cholesterol, refined grains, sweets, and red and processed meats (Taylor 2009; Noori 2014).
In an analysis of the nutrition data of more than 241 000 participants from three large population studies, each individual’s diet was graded for adherence to a low-sodium DASH-style diet. People with the highest scores, reflecting the closest adherence to DASH guidelines, were 40–45% less likely to develop kidney stones than people with the lowest scores (Taylor 2009).
In another study, 57 subjects with recurrent kidney stones and high urinary oxalate were randomly assigned to a low-sodium DASH diet or a low-oxalate diet group. Both diets were associated with improvements in urine chemistry with respect to kidney stone risk, but people on the DASH diet had higher urine pH (more alkaline urine) and greater urine citrate concentrations than those on the low-oxalate diet (Noori 2014). The DASH diet’s high citrate and calcium content may account for lower kidney stone risk among those adhering to this dietary approach (Taylor 2009).