Kidney stones are a common and painful condition, with over three million people seeking treatment for related symptoms every year. These hard masses of minerals form in the kidneys from crystals in the urine. While genetic predisposition can play a role, dietary and lifestyle choices are often significant contributing factors. This article outlines dietary choices to reduce the risk of developing kidney stones, including foods to eat and avoid.
Understanding Kidney Stones
Kidney stones form when urine output decreases, and the kidney contains large numbers of certain minerals that stick together. These minerals crystallize and combine into larger structures, forming hard deposits of insoluble salt crystals. Common types of kidney stones include calcium oxalate, calcium phosphate, struvite, uric acid, and cystine stones.
Several factors can cause kidney stones, including:
- High oxalate intake from certain foods
- A high protein diet
- Too much sodium
- Dehydration or low fluid intake
General Dietary Recommendations for Kidney Stone Prevention
People who wish to prevent kidney stones from developing for the first time or reduce the risk of recurrence should follow these main steps:
- Drink plenty of water
- Limit their intake of salt and animal protein
- Restrict foods that contain high levels of oxalates
- Get enough calcium
Most diet recommendations are based on stone types and individualized for each person. The most important aspect of managing diet when looking to prevent recurrent kidney stones is speaking to a doctor or dietitian. They will be able to identify the type of kidney stone that is developing and ways to slow or stop its development.
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The DASH Diet and Kidney Stone Prevention
Many dietitians and nephrologists recommend the Dietary Approaches to Stop Hypertension (DASH) diet for people with kidney stones. This diet has demonstrated the ability to reduce the risk of kidney stone formation and improve overall health, such as lower blood pressure and a reduced risk of heart disease, stroke, and cancer.
The DASH diet encourages people to consume vegetables, fruits, whole grains, and low-fat dairy. The plan also suggests limiting the intake of salt, sugar, and red meat.
Dietary Recommendations Based on Kidney Stone Type
Dietary changes mainly affect people at risk of calcium oxalate stones, calcium phosphate stones, uric acid stones, and cystine stones.
Calcium Oxalate Stones
Calcium oxalate stones are the most common type of kidney stone. Oxalate is naturally found in many foods, including fruits and vegetables, nuts and seeds, grains, legumes, and even chocolate and tea. High oxalate foods include peanuts, rhubarb, spinach, beets, Swiss chard, chocolate, and sweet potatoes.
Recommendations:
- Limit high-oxalate foods: If a person has had calcium oxalate stones, they may wish to restrict their intake of high oxalate foods, which may increase the risk of recurrence.
- Pair calcium-rich foods with oxalate-rich foods: Eat and drink calcium foods such as milk, yogurt, and some cheese and oxalate-rich foods together during a meal. The oxalate and calcium from the foods are more likely to bind to one another in the stomach and intestines before entering the kidneys, making it less likely that kidney stones will form.
- Maintain adequate calcium intake: A diet low in calcium actually increases your chances of developing kidney stones. The recommended calcium intake to prevent calcium stones is 1000-1200 mg per day. Calcium is not the enemy, but it tends to get a bad rap!
- Reduce sodium intake: Extra sodium causes you to lose more calcium in your urine. A high sodium diet can increase your chances of developing another stone. You can lower your sodium intake by choosing fresh low sodium foods which can help to lower calcium leakage in the urine and will also help with blood pressure control if you have high blood pressure.
Calcium Phosphate Stones
A high protein diet can contribute to the formation of calcium phosphate stones. They form when calcium combines with phosphorus in the urine.
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Recommendations:
- Limit animal proteins: organ meats (liver), dairy products, eggs, and seafood.
- Reduce processed foods: Phosphorus additives are often found in frozen meals, sodas, and deli meats.
- Reduce sodium intake.
Uric Acid Stones
Uric acid stones are another common type of kidney stone. Red meat, organ meats, and shellfish have high amounts of a natural chemical compound known as purines. High purine intake leads to a higher production of uric acid and a larger acid load for the kidneys to excrete.
Recommendations:
- Limit high-purine foods: Cut down on high-purine foods such as red meat, organ meats, beer/alcoholic beverages, meat-based gravies, sardines, anchovies, and shellfish.
- Follow a healthy diet plan: Emphasize vegetables and fruits, whole grains, and low-fat dairy products.
- Limit sugar-sweetened foods and drinks: Especially those that have high fructose corn syrup.
- Limit alcohol: Because it can increase uric acid levels in the blood.
- Avoid short-term diets: For the same reason.
Cystine Stones
Cystine stones are rare and result from excess cystine in the urine due to a hereditary condition.
Recommendations:
- Drink plenty of water to lower cystine levels.
- Reduce acidic foods.
- Try to eat less meat and increase fruit/vegetables to balance urine pH.
Foods to Include in a Kidney Stone Prevention Diet
Water
Including extra water in the diet can help prevent kidney stones, as they often occur due to dehydration. The National Institute for Diabetes and Digestive and Kidney Diseases (NIDDK) recommend drinking 6-8 glasses every day. Unless you have kidney failure, many health care professionals recommend that you drink six to eight, 8-ounce glasses a day. Extra water dilutes the substances in urine that lead to stones.
Calcium and Oxalate-Rich Foods
A person should include foods rich in calcium, especially if they consume many foods that are higher in oxalate, such as spinach. Calcium and oxalate bind together in the intestines, interrupting the formation of stones. Good sources of calcium include low-fat or fat-free milk products, calcium-fortified foods, beans, and calcium-rich vegetables, such as broccoli and seaweed.
Fruits and Vegetables
Increasing the number of vegetables in their diet can help a person prevent stone formation. Fruits can be dried, frozen, or fresh. Fruits with high levels of citric acid, such as oranges and lemons, have also demonstrated a positive effect in preventing kidney stones according to a 2014 review of studies.
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Fruits and vegetables high in citrate help stop calcium from building up in your child's urine. Some examples of citrate rich foods include bell pepper, carrots, grapefruit, grapes, kiwi, leafy greens, lemons (including lemon juice, when added to water), melons, oranges, pomegranates, and tomatoes.
Plant-Based Protein
Small amounts of animal-based proteins are safe to consume. However, too much animal protein can increase a person’s risk of kidney stones. Dietitians encourage the inclusion of plant-based protein sources in a kidney stone diet. Examples include beans, peas, and lentils.
Including plant-based proteins in place of some animal-based proteins can help reduce the risk of kidney stones. Some examples of plant-based proteins include beans, plant-based yogurt, lentils, quinoa, and tofu.
Omega-3 Fatty Acids
Foods rich in omega-3 fatty acids can help lower calcium levels in the urine and may reduce the risk of stone formation. Foods rich in omega-3 fatty acids include certain types of fish (mackerel, salmon), fish oil, and flaxseeds.
Whole Grains
Having your child eat more whole grains provides roughage, fiber, and micronutrients needed to absorb calcium from the blood and limit calcium excretion in the urine. Whole grains that are good for kidney health include barley, farro, and oats.
Foods to Limit or Avoid
High-Sodium Foods
Eating too much sodium can make your child’s body lose more calcium in their urine, which raises the risk of kidney stones. Excess salt increases the level of calcium in your urine. Sodium is in many canned, packaged, and fast foods. To help lower sodium intake, encourage your child to avoid foods with lots of added salt, including dressings, hamburgers, many items from fast food restaurants, processed foods, chicken nuggets, cheese crackers, hard cheeses, and lunch meats.
Sugary and Caffeinated Drinks
Energy drinks, some protein shakes and beverages with high fructose corn syrup, added sugars or caffeine can contribute to kidney stone formation. Cola should be avoided as it contains high levels of phosphate, another chemical that can promote kidney stone formation.
Calcium Supplements
Calcium supplements are restricted for your child living with kidney stones. It's important they get enough calcium from natural sources like dairy, leafy greens and fortified foods to support kidney and bone health.
High-Oxalate Foods
Foods naturally high in oxalates can increase the risk of oxalate stones. Eating too many of these foods may contribute to stone formation: chocolate, rhubarb, sweet potatoes, tea, and wheat bran.
Animal-Based Proteins/Processed Meat
Eating too much animal meat, like beef, pork, ham, sausages or sardines, can make urine more acidic.
Refined Sugar
Very reduced refined sugar intake is emphasized in the new government diet recommendations because of American obesity and diabetes. The recommendation is that less than 10% of all diet carbohydrates come in the form of added sugar which means very little sweets. This means sugars that are added to foods, not the natural sugars in fruits and some vegetables. The latter are absorbed more slowly and are safe.
Additional Tips for Kidney Stone Prevention
- Stay hydrated: Drink at least 12 glasses of water daily to stay hydrated.
- Consume citrus drinks: Such as orange juice, to increase citrate levels. Add lemon or lime to your water.
- Include calcium-rich foods: In every meal, at least three times a day.
- Limit animal protein intake: To reduce uric acid levels.
- Avoid excessive salt, sugar, and high-fructose corn syrup products.
- Steer clear of foods and drinks high in oxalates and phosphates.
- Avoid beverages that can cause dehydration, such as alcohol.
- Choose fresh alternatives that are low in sodium.
- Give preference to fish, poultry, or plant proteins.
- Get calcium from food (dairy products, leafy greens), not from supplements.
- Even healthy food (nuts, berries) can be dangerous in excess.
- Include whole grains in your diet, such as oats and quinoa (low oxalate content).
- Leafy greens are also very useful.
- Products with a high-water content are a must-have.
The Importance of Individualized Dietary Plans
Every person is different, and individual needs and dietary requirements will vary. There is no single diet plan for all types of kidney stones. Because kidney stones vary according to the minerals they contain, dietary recommendations will also vary. A person should talk to their doctor about which foods cause stones to help them determine what they should and should not eat to help avoid the formation of stones in the future.
Post-Surgery Dietary Guidelines
For individuals recovering from kidney stone surgery, following the treatment plan and dietary recommendations from specialists can significantly enhance recovery and help prevent recurrence.
Adequate fluid intake, especially water, dilutes the chemicals that form kidney stones. Patients are advised to drink at least 12 glasses of water daily to reduce the risk of recurrence.