Preventing oxalate kidney stones
Wednesday, June 20, 2018
Q: Do you have suggestions for a diet to prevent calcium oxalate kidney stones? I have been getting conflicting information. — E.L., Greenville
A: I am pleased that Kara Massotti will answer your question. Kara returns to Greenville from her dietetic internship and master’s in nutrition from the University at Buffalo in New York. Joining Kay Craven, she will be seeing patients for nutrition counseling at the ECU Family Medicine Center. Kara is a 2016 graduate of ECU who volunteered with us as a student. In her free time, she enjoys going to the gym, taking part in boxing classes and taking walks. Here is what she wants you to know about oxalate kidney stones and nutrition.
Despite what you would think, dietary calcium does not affect the amount of calcium in the urine, and a low-calcium diet has no benefit in preventing kidney stones. In people with calcium oxalate kidney stones, we recommend a low-oxalate diet and high-citrate diet because these have both been shown to reduce the risk of calcium oxalate kidney stones.
One in 10 people in the general population has kidney stones. Kidney stones are made up of calculi, salts and minerals that form crystals within the urinary tract. Men are more likely to suffer from kidney stones than women, and they most often occur between the ages of 40 and 60. When untreated, kidney stones can cause blood in the urine, severe pain, urinary tract and kidney infections and eventually loss of kidney function.
Calcium oxalate stones are the most common type of stones in the U.S. Normally, extra calcium that isn’t used by the bones or the muscles goes to the kidneys and is flushed out of the body in the urine. However, when urine calcium is too high — usually because of another underlying disease — it stays in the kidneys and joins with other waste products to form a stone.
A low-oxalate diet, which is a diet low in salt and acid, can help prevent the formation of calcium oxalate stones. Some low-oxalate foods you can consider including in your diet are beans, dried peas and lentils. However, oxalate is naturally found in so many foods it is almost impossible to avoid. If want to try to limit high-oxalate foods, avoid dark colas, black tea, nuts and nut butters, spinach, chocolate and potatoes, chips and fries.
Next, incorporate more citrate into your diet. Citrate, an alkali, inhibits the formation of calcium oxalate stones by binding to calcium in the urine and preventing the formation of crystals. The best sources of citrate are lemons and limes, and other citrus fruits and fruit juices such as oranges, grapefruits and berries. However, for overall health, we recommend eating the whole fruit instead of drinking juice.
If you reduce your intake of animal protein, such as beef, chicken, pork, organ meats, eggs, fish, shellfish, milk and cheese, it might help too. Vegetarians form kidney stones at one-third the rate of those who eat animal protein (a good reason to avoid a ketogenic diet). If you eat meat two meals a day, try eating only one serving. Or try having one or two meatless days a week.
Making sure you get no more than 2,300 mg of salt per day can also help prevent stones. That may mean limiting processed foods, restaurant foods and fast foods. Other high-salt foods are hot dogs, sausage, chips, frozen meals, canned soups and vegetables, pickles, olives, canned or bottled pasta sauces, some condiments, baked goods and pizza. Read the Nutrition Facts label.
Perhaps the most important recommendation is drinking at least 2 liters of fluid per day. Try lemonade made with real lemon juice and use a sugar substitute if you must sweeten it. Increasing fruits and vegetables helps increase potassium and decrease sodium — just like in the DASH diet — known to prevent stone formation and give you other great health benefits.
If someone gave you information recommending a low-calcium diet, it’s likely that the information is out of date. Although it may seem unusual, a higher dietary calcium intake has been associated with lower incidence of kidney stone disease. We recommend a calcium intake of 1,200-1,500 mg per day.Some calcium-rich sources to include at each meal are milk, yogurt, calcium-fortified orange juice, low-fat natural cheeses (such as cheddar, mozzarella and Swiss), calcium-fortified cereals, broccoli and oranges.
In this case, food is much better than supplements since they have been associated with a small increase in risk for kidney stones. As mentioned earlier, it is almost impossible to avoid oxalate in food. If you eat a food rich in calcium at the same time as one high in oxalate, the calcium and oxalate bind together in the stomach rather than in the kidney, reducing the risk for oxalate kidney stones.
Other diseases, such as eating disorders, food intolerances and malabsorptive conditions, can also put you at risk for kidney stones. Talk to your doctor if you have concern about these diseases or a family history of kidney stones. If you change the foods and beverages in your diet, you would benefit from a consultation with a registered dietitian nutritionist to ensure you are getting the nutrients you need within your calorie allotment.
Professor emeritus Kathy Kolasa, a registered dietitian nutritionist and Ph.D., is an Affiliate Professor in the Brody School of Medicine at ECU. Contact her at firstname.lastname@example.org.