That trendy, high-protein diet could be increasing your risk of kidney stones (2024)

You might remember the scene in the ’90s sitcom Friends where Joey is lying in a hospital bed struggling to pass a kidney stone while Phoebe, in a separate room at the very same time, is giving birth to triplets. As the story switches between the two rooms, the two friends’ cries and yowls of pain are matched.

Although it’s a funny scene, the excruciating pain that accompanies kidney stones is not a laughing matter. Kidney stone pain lands more than half a million people in emergency rooms each year, the National Kidney Foundation reports, and incidences of kidney stones have been continually increasing, even in kids.

While there may be many factors to blame for this, there’s one that researchers agree on: diet. A diet high in animal protein can increase your risk of developing kidney stones, the American Urologic Association states, and several studies back this up.

The Recommended Dietary Allowance for protein is a 0.36 grams per pound of body weight. In a balanced diet, protein should account for between 10% and 35% of all calories consumed. For an adult who weighs 150 pounds, that's about 54 grams of protein a day. High-protein diets commonly include around 75 grams of protein a day, or even as much as more than 100 grams.

Wondering what else might increase your risk of the dreaded stones, and what the heck kidney stones are made of to begin with? Here to answer your questions is Dr. Phillip Marks, a urologist at Novant Health Urology - Wilmington.

What exactly are kidney stones?

Kidney stones are hard deposits that can form in your kidneys, two bean-shaped organs in your upper abdomen, each about the size of your fist, that make up part of the upper urinary tract. Your kidneys are responsible for filtering waste products and excess water from the bloodstream to form urine. Kidney stones are made from different minerals and salts.

The four types of kidney stones are:

1. Calcium stones, 80% of stones. Calcium stones may be made of calcium oxalate or calcium phosphate, with calcium accounting for a large majority.
2. Uric acid stones, 5% to 10% of stones. Uric acid is a waste product that comes from chemical changes in the body. Uric acid crystals do not dissolve well in acidic urine and instead will form a uric acid stone.
3. Struvite stones, 10% of stones. These are related to chronic urinary tract infections (UTIs). Some bacteria make the urine less acidic, which allows these stones to grow.
4. Cystine stones, less than 1% of stones. Cystinuria (too much cystine in the urine) is a rare, inherited metabolic disorder. The kidneys do not reabsorb cystine from the urine in people who have this. When high amounts of cystine are in the urine, it causes stones to form.

Is it important to know what type of stone I have?

Marks explained that knowing the composition of the stone is important for managing treatment and prevention. “However,” he continued, “this does not necessarily tell you how you made it.”

So successful kidney stone treatment and prevention isn’t just about determining a stone’s composition; it also involves diving into a person’s medical and lifestyle history to examine what is causing the formation of the stone.

“There's usually some sort of metabolic inborn error, along with other medical problems, and lifestyles that will contribute to the formation of stone disease,” Marks said. “So getting to the root cause is important.”

And that’s where Marks and other Novant Health urologists come in. They can run tests to help determine the root cause of the stone formation, which is important to ensure one kidney stone doesn’t become many over time.

“We’ll come up with a treatment plan that will manage that and help prevent future stone episodes. That's the goal,” Marks said.

What are the risk factors for kidney stones?

Just as there are several types of kidney stones, there are also several different risk factors. The primary risk factor, Marks said, is in your genes.

“It is generally considered a genetic disease,” Marks said. “Just like high blood pressure or like diabetes, it's mostly familial in origin.”

In fact, this is why the Southeastern U.S. has higher numbers of kidney stone sufferers and is referred to as the “Stone Belt,” Marks continued. It’s primarily due to genetics. Added aggravating factors are the high temperatures that can lead to dehydration and high mineral content in the soil, which leaches into the water.

And yes, that high-protein diet we talked about is a risk factor, too. Trendy diets that rely heavily on protein while limiting carbohydrates – like Atkins, paleo and ketogenic – can raise your risk of kidney stones in several ways. First, animal protein raises acid levels in urine, which makes it easier for calcium oxalate and uric acid stones to form. Second, the breakdown of meat into uric acid raises the chance that both calcium and uric acid stones will form, according to the American Urological Association. Third, high-protein diets can reduce citrate levels in the body, and citrate helps prevent kidney stones from forming. Last, high-protein diets can cause a buildup of protein in the blood.

Certain chemotherapy drugs can also increase your risk of kidney stones, as can gastric bypass surgery, or inflammatory bowel disease.

Why do kidney stones hurt so much?

A kidney stone may be as small as a grain of sand or as large as a golf ball. For some lucky people, they can pass a kidney stone while urinating without even knowing it. For other people, the kidney stone becomes trapped inside the ureter, the tube that carries urine from the kidney to the bladder. When this system is trying to push urine out and there is something blocking it, this can cause intense pain, often in “waves” across the sides, back and groin. This painful backup of urine flow from the kidney is called hydronephrosis.

What are the signs I might have a kidney stone?

Often the first sign that people respond to is the pain, Marks said, which can start off moderate at first before it grows.

“You might have some pain or discomfort in your flank, bladder area or back,” he said. “But sometimes it's recurrent urinary tract infections or sometimes it's blood that is either visible or not visible in urine on a routine check.”

If a urinalysis reveals blood in the urine, Marks recommends further evaluation, which may include an X-ray and/or a physical exam.

Marks emphasized that keeping up with routine health screenings with your primary care physician can help prevent problems with kidney stones because they can be detected and managed well before they reach problematic pain levels, which often lands people in the emergency room.

“Ideally, it would be best to take a preemptive strike and evaluate whether you’ve got stone disease, and then we can do appropriate follow-up or management,” Marks said.