Kidney stones can not only cause excruciating pain but are also associated with chronic kidney disease, osteoporosis and cardiovascular disease. If you’ve had a kidney stone once, you have a 30% chance of developing another kidney stone within five years.
Dietary changes are often recommended to prevent recurrent symptomatic kidney stones. However, little research is available on dietary changes for those with one episode of kidney stone formation versus those with recurrent ones.
Mayo Clinic researchers designed a prospective study to investigate the effects of dietary changes. Their findings show that enriching the diet with foods high in calcium and potassium can prevent recurrent symptomatic kidney stones.
Dietary factors were based on a questionnaire administered to 411 patients who experienced kidney stones for the first time and a control group of 384 — all of whom were seen between 2009 and 2018 at the Mayo Clinic in Rochester and the Mayo Clinic in Florida. The results, which were published Proceedings of the Mayo Clinicshowed that low dietary calcium and potassium, as well as low fluid, caffeine, and phytate intake, were associated with a higher likelihood of experiencing a first symptomatic kidney stone.
Among patients who developed stones for the first time, 73 experienced recurrent stones during a median follow-up of 4.1 years. Further analysis showed that low levels of dietary calcium and potassium predicted recurrence.
“These dietary findings may be of particular importance because recommendations for kidney stone prevention are primarily based on dietary factors associated with first-time rather than recurrent stone formation,” said Andrew Rule, MD, a Mayo Clinic nephrologist and senior author of the study. “Patients may not be likely to adjust their diet to prevent the occurrence of kidney stones, but they are more likely to do so if it helps prevent recurrence.”
Fluid intake of less than 3,400 milliliters per day, or about nine 12-ounce glasses, was associated with first-time stone formation along with caffeine intake and phytate, the study found. Daily fluid intake includes eating foods like fruits and vegetables.
Low fluid and caffeine intake can lead to low urine output and increased urine concentration, which contributes to stone formation. Phytate is an antioxidant compound found in whole grains, nuts, and other foods that may increase calcium absorption and urinary calcium excretion.
“Changing your diet to prevent kidney stones can be very difficult,” says Dr. Rule. “Therefore, knowing the most important dietary factors for preventing kidney stone recurrence can help patients and providers know what to prioritize.”
Low dietary calcium and potassium were a more important predictor than fluid intake of recurrent kidney stone formation, said AP Cheucharat, first author of the article and a Mayo Clinic postdoctoral research fellow at the time of the study. “This is not to say that high fluid intake is not important. We did not find a benefit of increasing fluid intake in patients with a history of kidney stones.”
The study concluded that a diet with a daily calcium intake of 1,200 mg may help prevent first and recurrent kidney stones. That daily intake is in line with the Department of Agriculture’s Daily Recommended Dietary Allowance.
Although a high potassium intake is also recommended, the USDA does not recommend a daily potassium intake. The study does not recommend an intake level.
Dr. Cheuchart says the consensus is that patients should add more fruits and vegetables that are high in calcium and potassium to their diet. Fruits that are high in potassium include bananas, oranges, grapefruit, cantaloupes, honeydew melon, and apricots. Vegetables include potatoes, mushrooms, peas, cucumbers and zucchini.
Co-author Dr. Rule and Cheuchrat are Charat Thongprayun, MD; Lisa Vaughn; Ramila Mehta; Philip Schulte, PhD; Helen O’Connor; and John Lieske, MD — all of Mayo Clinic — and Erin Taylor, MD, VA Maine Health Care System. Dr. Schulte is affiliated with OxThera Inc. outside of this research work. Reported personal fees from Dr. Lieske reports grants and/or other fees from pharmaceutical and related companies identified in the article — which are outside of this study and all to the Mayo Clinic. The other authors report no competing interests.