Tag Archives: kidney

Diets rich in these minerals may help prevent recurrent kidney stones

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Kidney stones can cause not only excruciating pain but also are associated with chronic kidney disease, osteoporosis and cardiovascular disease. If you’ve experienced a kidney stone once, you have a 30% chance of having another kidney stone within five years.

Changes in diet are often prescribed to prevent recurrent symptomatic kidney stones. However, little research is available regarding dietary changes for those who have one incident of kidney stone formation versus 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 high in calcium and potassium may prevent recurrent symptomatic kidney stones.

Dietary factors were based on a questionnaire administered to 411 patients who had experienced first-time symptomatic kidney stones 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 lower dietary calcium and potassium, as well as lower intake of fluids, caffeine and phytate, are associated with higher odds of experiencing a first-time symptomatic kidney stone.

Of the patients who had first-time stone formation, 73 experienced recurrent stones within a median of 4.1 years of follow-up. Further analysis found that lower levels of dietary calcium and potassium predicted recurrence.

“These dietary findings may have 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, M.D., a Mayo Clinic nephrologist and senior author of the study. “Patients may not be likely to adjust their diet to prevent an 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 intake and phytate, the study finds. Daily fluid intake includes intake from foods such as fruits and vegetables.

Low fluid and caffeine intake can result in low urine volume and increased urine concentration, contributing to stone formation. Phytate is an antioxidant compound found in whole grains, nuts and other foods that can lead to increased calcium absorption and urinary calcium excretion.

“Changing your diet to prevent kidney stones can be very difficult,” says Dr. Rule. “Thus, knowing the dietary factors that are most important for 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, M.D., the article’s first author and a postdoctoral research fellow at Mayo Clinic at the time of the study. “This is not to say high fluid intake is not important. We just did not find benefits of increasing fluid intake among those patients with a history of kidney stone formation.”

The study concludes that diets with daily intake of 1,200 milligrams of calcium may help prevent first-time and recurrent kidney stones. That daily intake is in line with the Department of Agriculture’s daily recommended nutrition.

While higher potassium intake also is recommended, the USDA does not make a recommendation for daily potassium intake. The study also doesn’t recommend an intake level.

Dr. Chewcharat says the takeaway is that patients should add more fruits and vegetables that are high in calcium and potassium to their diets. Fruits that are high in potassium include bananas, oranges, grapefruits, cantaloupes, honeydew melons and apricots. Vegetables include potatoes, mushrooms, peas, cucumbers and zucchini.

Polluted air may pose great threat to your kidneys, says study

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There is good evidence that polluted air increases the risk of respiratory problems such as asthma — as well as organ inflammation, worsening of diabetes and other life-threatening conditions. But new research suggests air pollution can also fuel something else: chronic kidney disease, or CKD, which occurs when a person’s kidneys become damaged or cannot filter blood properly.

Recently published in PLOS ONE, a University of Michigan study highlights the lesser-known connection.

“Similar to smoking, air pollution contains harmful toxins that can directly affect the kidneys,” says Jennifer Bragg-Gresham, M.S., Ph.D., a Michigan Medicine epidemiologist and the study’s lead author.

“Kidneys have a large volume of blood flowing through them, and if anything harms the circulatory system, the kidneys will be the first to sense those effects.”

People with diabetes, obesity, high blood pressure or heart disease are at increased risk of developing CKD. Which is why high-risk patients who live in heavily populated or polluted areas should recognize the danger and take precautions, Bragg-Gresham says.

Why air pollution is dangerous?

Air pollution contains fine particulate matter, or PM2.5, which is a cocktail of microscopic particles.

Because these particles are virtually weightless, they can stay in the air longer, causing humans to unavoidably inhale them on a regular basis without knowing it. PM2.5 can lead to serious health effects when inhaled often.

By reviewing Medicare claims data and air-quality data from the Centers for Disease Control and Prevention, the study’s authors found a positive association between CKD rates and PM2.5 concentration.

Says study co-author Rajiv Saran, M.D., a Michigan Medicine nephrologist and director of the United States Renal Data System Coordinating Center at U-M: “If you look at areas that are heavily polluted versus areas that are less polluted, you will find more chronic kidney disease.”

According to figures cited in the new research, chronic kidney disease afflicts more than 27 million Americans. People with CKD have an eightfold increased risk of cardiovascular mortality.

Unfortunately, PM2.5 is almost impossible to avoid.

We encounter air pollution from many simple everyday activities, such as cooking and driving. Other contributors are smoking, burning wood, packaged spray products, household appliances and, perhaps the most obvious, industry and vehicle emissions.

Air pollution also contains heavy metals such as lead, mercury and cadmium — all of which are known to negatively affect the kidneys.

Problems and preventive measures

The U-M research examined several prior studies on the issue, including an effort conducted in select coal-mining areas of Appalachia that found a 19 percent higher risk of CKD among men and a 13 percent higher risk in women compared with those who lived in counties with no mining.

The good news: PM2.5 levels are much lower in the U.S. than in other industrialized countries such as China and India.

“What this means for the countries with higher PM2.5 is significantly higher odds of CKD,” says Bragg-Gresham, also an assistant research scientist at U-M. “Our research was only able to examine a small range of PM2.5 values present in America but was able to find a significant association.”

However, it’s still important to take precautions when exposed to air pollution, especially for people who have existing health conditions or who live in densely populated or polluted cities.

“In heavily polluted areas, consider wearing masks that cover your nose and mouth, limit hours outside and limit long hours commuting to work in high traffic as well,” Saran says, adding that the risk should be taken seriously.

“Many people don’t see the seriousness of air pollution because it isn’t something visible, but that doesn’t mean it’s any less important for your health.”