What Causes Recurrent Stones & How Diet Contributes
Recurrent kidney stones can develop every two to four years. The reasons that stones recur can be a combination of several factors, including habits, diet, heredity, and chance. No two patients are the same, but for every patient, prevention is important.
Your doctor can help you look at your current habits and diet to see where changes could be made. For this reason, it’s important to have as much information as you can about your medical history and medications, your family history, and your eating and drinking habits. For example, increased salt consumption could result in higher calcium levels in your urine, which contributes to stone formation. You’ll also need to look beyond salt intake at fluids, calcium, protein, sugar, and oxalate intake.
About Oxalate
Oxalate is a natural substance. It binds to calcium during the digestive process. Oxalate that is not bound to calcium travels to the kidneys to be passed out via urine. However, if there is too little liquid in the kidneys, the oxalate fragments create crystals that become stones. The majority of stones are calcium oxalate stones.
Oxalate Diet Modifications
If your doctor recommends limiting oxalate as part of diet modification for recurring stones, there are some foods to be mindful of. Spinach and rhubarb, for example, are very high in oxalate. Other high oxalate foods include wheat berries, baked potatoes (with skin), soy flour, navy beans, beets, cocoa powder, raspberries, avocados, oranges, dates, and kiwi.
Keep in mind that you likely don’t need to avoid these foods completely, but you will need to be mindful of how much oxalate you are eating each day, and make sure you are getting enough calcium in your diet.
Some lower oxalate meals:
Breakfast: Eggs; yogurt with blueberries
Lunch: Sandwich with thin slices of bread or a wrap; salad made with romaine and iceberg lettuce
Dinner: Chicken, beef, or fish; rice; cauliflower
Helpful Resources
courtesy of The Harvard School of Public Health
Calcium Amounts
Taking the right amount of calcium can help to keep your oxalate levels from rising. Here’s the recommended daily allowance (RDA) of calcium based on sex and age:
Men:
19-50 years: 1,000 mg
51-70 years: 1,000 mg
71 and older: 1,200 mg
Women:
19-50 years: 1,000 mg
51 and older: 1,200 mg
The daily upper limit for calcium can range from 2,000 mg to 2,500 mg, so talk with your doctor to make sure that you are getting a safe amount.
You can find calcium in dairy products, soft-boned fish (salmon), dark leafy vegetables, and fortified foods and beverages. Your body also needs vitamin D to efficiently absorb calcium, so make sure you are getting a safe amount of SPF-protected sun exposure and eating fortified foods with vitamin D.
Low-Sodium Diet
If you are prone to kidney stones, your doctor might suggest that you follow a low-sodium diet.
You should stay under 2,300 mg of sodium intake, and under 1,500 mg if you have experienced kidney stones in the past that have been attributed to sodium. To cut back on sodium, avoid adding extra salt to meals and cut back on processed foods.
As an added benefit, reducing your sodium intake is good for your cardiovascular health and blood pressure.
Animal Protein & Citrate
A high acid concentration in the urine can be too much for the kidneys to excrete, which can contribute to the formation of uric acid stones. Although a high level of uric acid typically occurs when the kidneys are not eliminating uric acid efficiently due to other conditions, a diet that is high in purine (a natural compound found in animal protein) can also contribute. Organ meats, shellfish, red meat, poultry, and eggs can be considered part of a high-protein diet.
A high-protein diet also reduces levels of citrate, which is a chemical that helps to prevent the formation of stones. Citrate in urine can prevent calcium from binding with other materials that contribute to stones. Lemons and limes are good sources of citrate, or citric acid, followed by grapefruits and oranges.