Aim:
To compare dietary factors between incident symptomatic stone formers and controls, and between incident stone formers, to determine whether dietary factors were predictive of symptomatic recurrence.
Patients and methods:
We prospectively recruited 411 local incident symptomatic kidney stone formers (validated by medical record) and 384 controls who were seen at Mayo Clinic in Minnesota or Florida between January 1, 2009 and August 31, 2018. Dietary factors were based on a Viocare, Inc. Food Frequency Questionnaire administered during an initial in-person study visit.
Logistic regression compared dietary risk factors between incident symptomatic stone formers and controls. Incident stone formers were followed for validated symptomatic recurrence in the medical record. Cox proportional hazards models estimated the risk of symptomatic recurrence with dietary factors. Analyzes adjusted for fluid intake, energy intake, and non-dietary risk factors.
Results:
In fully adjusted analyses, lower dietary calcium, potassium, caffeine, phytate, and fluid intakes were associated with a higher likelihood of an incident symptomatic kidney stone.
Among incident stone formers, 73 experienced symptomatic recurrence during a median of 4.1 years of follow-up. When adjusting for body mass index, fluid intake, and energy intake, lower dietary calcium and potassium intake predicted symptomatic kidney stone recurrence.
With additional adjustment for non-dietary risk factors, lower dietary calcium intake remained a predictor of recurrence, but lower potassium intake only remained a predictor of recurrence among those not taking thiazide diuretics or calcium supplements.
Conclusion: Enriching the diets of stone formers with foods rich in calcium and potassium may help prevent recurrent symptomatic kidney stones. |
Comments
Kidney stones can cause not only excruciating pain, but are also associated with chronic kidney disease, osteoporosis, and cardiovascular disease. If you have experienced a kidney stone once, you have a 30% chance of having another kidney stone within five years.
Dietary changes are often prescribed to prevent recurrent symptomatic kidney stones. However, there is little research available regarding dietary changes for those who have one incident of kidney stone formation compared to those who have recurrent incidents.
Mayo Clinic researchers designed a prospective study to investigate the impact of dietary changes. Their findings show that enriching diets with foods rich in calcium and potassium can prevent recurrent symptomatic kidney stones.
Dietary factors were based on a questionnaire administered to 411 patients who had experienced symptomatic kidney stones for the first time and a control group of 384 people, all of whom were seen at Mayo Clinic in Rochester and Mayo Clinic in Florida between 2009 and 2018.
The findings, which were published in Mayo Clinic Proceedings , show that a diet lower in calcium and potassium, as well as lower fluid, caffeine, and phytate intake, are associated with higher odds of experiencing a symptomatic kidney stone for the first time.
Of the patients who had stone formation for the first time, 73 experienced recurrent stones over a median of 4.1 years of follow-up. A subsequent analysis found that lower levels of dietary calcium and potassium predicted recurrence.
"These dietary findings may be of particular importance because recommendations for preventing kidney stones have been based primarily on dietary factors associated with first-time rather than recurrent stone formation," says Andrew Rule, MD, a nephrologist at Mayo Clinic and lead author of the study. "Patients may not adjust their diet to prevent the incidence of kidney stones, but they are more likely to do so if it can help prevent recurrence."
Fluid intake of less than 3,400 milliliters per day, or about nine 12-ounce glasses, is associated with first-time stone formation, along with caffeine and phytate intake, the study finds. Daily fluid intake includes the intake of foods such as fruits and vegetables.
Low fluid and caffeine intake can result in low urine volume and increased urine concentration, which contributes to stone formation. Phytate is an antioxidant compound found in whole grains, nuts, and other foods that can increase calcium absorption and urinary calcium excretion.
"Changing your diet to prevent kidney stones can be very difficult," says Dr. Rule. "Therefore, knowing the dietary factors that are most important in preventing kidney stone recurrence can help patients and providers know what to prioritize."
Low dietary calcium and potassium was a more important predictor than fluid intake of recurrent kidney stone formation
Says Api Chewcharat, MD, first author of the paper and a postdoctoral researcher at Mayo Clinic at the time of the study. "This is not to say that high fluid intake is not important. We simply found no benefit from increasing fluid intake among patients with a history of kidney stone formation."
The study concludes that diets with a daily intake of 1,200 milligrams of calcium can help prevent first-time and recurrent kidney stones. That daily intake is in line with the daily nutrition recommended by the Department of Agriculture.
While increased potassium intake is also recommended, the USDA does not make a recommendation for daily potassium intake. The study also does not recommend an intake level.
Dr. Chewcharat says the lesson is that patients should add more fruits and vegetables high in calcium and potassium to their diets. Fruits high in potassium include bananas, oranges, grapefruits, cantaloupes, honeydew melons, and apricots. Vegetables include potatoes, mushrooms, peas, cucumbers and zucchini.
Co-authors with Drs. Rule and Chewcharat are Charat Thongprayoon, MD; Lisa Vaughan; Ramila Mehta; Phillip Schulte, PhD; Helen O’Connor; and John Lieske, MD, all of Mayo Clinic, and Erin Taylor, MD, of VA Maine Healthcare System. Dr. Schulte reports personal fees from OxThera Inc. outside of the work on this study. Dr. Lieske reports grants and/or other fees from pharmaceutical and related companies identified in the article, all outside of this study and all paid to Mayo Clinic. The other authors report no competing interests.
