Kidney stones are mineral deposits that crystallize within the kidneys. They occur in nearly 15% of individuals, with a 50% recurrence rate. Though generally treatable and temporary, they are often painful. The stones typically form when the urine contains excess uric acid, calcium, and oxalates, minerals that can form crystals. In some cases, even if the mineral content in urine is not too high, the fluid lacks substances that prevent crystallization. Since the composition of urine is largely dependent upon diet, abstaining from certain foods can lower the risk of kidney stones.
Since oxalates form a large percentage of kidney stone make-up, consuming oxalate-rich foods is likely to trigger stone formation in people with a history of kidney stones. Some ingredients to avoid or limit include
- Swiss chard
- Sweet potatoes
Those who have already experienced kidney stones may want to completely cut these foods from their diets, and people with a family history should also limit or remove foods high in oxalates.
Animal proteins, including fish and eggs, contain purines that release uric acid, a large component of kidney stones. The risk of calcium stones also increases with excess consumption of animal proteins, because the breakdown of these foods causes a high excretion of calcium and low excretion of citrate (which neutralizes calcium). The Dietary Approaches to Stop Hypertension (DASH) diet emphasizes fruits and vegetables while limiting dairy and animal protein. It has been shown to reduce the risk of kidney stones.
To a large extent, sodium intake determines the amount of calcium excreted in the urine. People eating high-sodium foods are more prone to developing calcareous kidney stones than compared to those on a low-sodium diet. Less than 2300 mg per day is the ideal amount of salt and sodium-rich foods, though doctors may suggest different limits based on the individual constitution. Avoiding processed or “fast” foods can significantly decrease sodium consumption, as can opting for seasonings other than salt when possible.
Foods containing fructose lead to the release of more calcium and uric acid and reduce the amount of fluid in the urine. This significantly increases the risk of developing kidney stones. While the natural fructose content in fruits is less likely to cause problems, be aware of the sugar’s inclusion in syrups, fruit juices, and other sweet substances.
Many studies point to links between artificial sweeteners and poor kidney function. High consumption may hamper the kidneys’ ability to perform optimally, preventing the filtering out of kidney stone-causing calcium, uric acid, and oxalates. Thus, zero-calorie sweeteners and diet sodas are poor fructose alternatives for those prone to kidney stones. Stevia may be the safest replacement for fructose.
Some studies link kidney stones in women to the use of calcium supplements, though not all medical professionals agree. Many doctors recommend eating calcium-rich foods to prevent the formation of stones. Those taking calcium supplements should take them after meals, as this improves absorption and reduces the risk of stones.
Soda, bottled juice, and energy drinks people at a higher risk of developing kidney disease. Soda elevates insulin levels and increases susceptibility to kidney stones, and can increase the risk of kidney stones by nearly 25%. People who turn to these beverages because they prefer alternatives to plain water should try adding citrus, berries, or other natural fruits or vegetables to their water, rather than choosing processed drinks.
Non-dairy foods that are high in calcium can lessen the chance of developing kidney stones. While dairy products such as milk and yogurt help build strong bones and have many other benefits, they can increase the risk of crystalized deposits by increasing the amount of calcium in the urine and impeding urination.
Caffeine can stress the kidneys, making them less efficient at filtering excess calcium and uric acid and contributing to the development of kidney stones. Though some studies support the benefits of moderate caffeine intake, drinking excessive amounts of coffee causes increases in blood pressure which could cause kidney issues.
Sardines are high in purines, a substance that greatly contributes to the formation of kidney stones. Manufacturers often increase a food’s aroma by adding purines during the production process. People who have had kidney stones in the past or who know they are at risk should avoid foods high in purines.