Treating Kidney Stones with Diet

Studies suggest that excessive consumption of animal protein poses a risk of kidney stone formation, likely due to the acid load contributed by the high content of sulfur-containing amino acids in animal protein, a topic I explore in my video, Preventing Kidney Stones with Diet. What about treating kidney stones, though? I discuss that in How to Treat Kidney Stones with Diet. Most stones are calcium oxalate, formed like rock candy when the urine becomes supersaturated. Doctors just assumed that if stones are made out of calcium, we simply have to tell people to reduce their calcium intake. That was the dietary gospel for kidney stone sufferers until a 2002 study published in the New England Journal of Medicine pitted two diets against one another—a low-calcium diet versus a diet low in animal protein and salt. The restriction of animal protein and salt provided greater protection, cutting the risk of having another kidney stone within five years in half.

What about cutting down on oxalates, which are concentrated in certain vegetables? A recent study found there was no increased risk of stone formation with higher vegetable intake. In fact, greater dietary intake of whole plant foods, fruits, and vegetables were each associated with reduced risk independent of other known risk factors for kidney stones. This means we may get additional benefits bulking up on plant foods in addition to just restricting animal foods.

A reduction in animal protein not only reduces the production of acids within the body, but should also limit the excretion of urate, uric acid crystals that can act as seeds to form calcium stones or create entire stones themselves. (Uric acid stones are the second most common kidney stones after calcium.)

There are two ways to reduce uric acid levels in the urine: a reduction of animal protein ingestion, or a variety of drugs. Removing all meat—that is, switching from the standard Western diet to a vegetarian diet—can remove 93% of uric acid crystallization risk within days.

To minimize uric acid crystallization, the goal is to get our urine pH up to ideally as high as 6.8. A number of alkalinizing chemicals have been developed for just this purpose, but we can naturally alkalize our urine up to the recommended 6.8 using purely dietary means. Namely, by removing all meat, someone eating the standard Western diet can go from a pH of 5.95 to the goal target of 6.8—simply by eating plant-based. As I describe in my video, Testing Your Diet with Pee & Purple Cabbage, we can inexpensively test our own diets with a little bathroom chemistry, for not all plant foods are alkalinizing and not all animal foods are equally acidifying.

A Load of Acid to Kidney Evaluation (LAKE) score has been developed to take into account both the acid load of foods and their typical serving sizes. It can be used to help people modify their diet for the prevention of both uric acid and calcium kidney stones, as well as other diseases. What did researchers find? The single most acid-producing food is fish, like tuna. Then, in descending order, are pork, then poultry, cheese (though milk and other dairy are much less acidifying), and beef followed by eggs. (Eggs are actually more acidic than beef, but people tend to eat fewer eggs in one sitting.) Some grains, like bread and rice, can be a little acid-forming, but pasta is not. Beans are significantly alkaline-forming, but not as much as fruits or even better, vegetables, which are the most alkaline-forming of all.

Through dietary changes alone, we may be able to dissolve uric acid stones completely and cure patients without drugs or surgery.

To summarize, the most important things we can do diet-wise is to drink 10 to 12 cups of water a day, reduce animal protein, reduce salt, and eat more vegetables and more vegetarian.

Want to try to calculate their LAKE score for the day? Just multiply the number of servings you have of each of the food groups listed in the graph in the video times the score. 

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

The Best Diet to Prevent Kidney Stones

In my video How to Prevent Kidney Stones With Diet, you can see what the jagged surface of a kidney stone looks like under a microscope. Imagine one of those scraping down your urinary canal! Kidney stones affect approximately 1 in 11 people in the United States. Twenty years ago it was only 1 in 20, representing a dramatic increase in the prevalence of the disease that started rising after World War II. Our first clue as to why was a study published in the 70’s, which found a striking relationship between stone incidence and the consumption of animal protein. This was a population study, though, so it couldn’t prove cause and effect.

That study inspired researchers in Britain to do an interventional study, adding animal protein to subjects’ diets, such as an extra can of tuna fish a day, and measuring stone-forming risk factors in their urine. Participants’ overall probability of forming stones increased 250% during those days they were eating that extra fish. And, the so-called “high animal protein diet” was just enough to bring intake up to that of the average American. So, Americans’ intake of meat appears to markedly increase the risk of kidney stones.

What about consuming no meat at all? By the late 70’s, we knew that the only dietary factor consistently associated with kidney stones was animal protein. The higher the intake of animal protein, the more likely the individual was to not only get their first kidney stone, but to then suffer from subsequent multiple stones. This effect was not found for high protein intake in general, but specifically high animal protein intake. Conversely, a diet low in animal protein may dramatically reduce the overall probability of forming stones. This may explain the apparently low incidence of stones in vegetarian societies; so, researchers advocated “a more vegetarian form of diet” as a means of reducing the risk.

It wasn’t until 2014 that vegetarian kidney stone risk was studied in detail, though. Using hospital admissions data, researchers found that vegetarians were indeed at a lower risk of being hospitalized for kidney stones. It’s not all or nothing, though. Among meat-eaters, increasing meat intake is associated with a higher risk of developing kidney stones, whereas a high intake of fresh fruit, fiber, and magnesium may reduce the risk. 

Which animal protein is the worst? People who form kidney stones are commonly advised to restrict the intake of red meat to decrease stone risk, but what about chicken and fish? Despite compelling evidence that excessive animal protein consumption enhances the risk of stone formation, the effect of different sources of animal protein had not been explored until another study in 2014. Researchers compared the effects of salmon and cod, chicken breast meat, and burger and steak. In terms of uric acid production, they found that gram for gram fish may actually be worse. However, the overall effects were complex. Basically, stone formers should be counseled to limit the intake of all animal proteins, and not by just a little bit. Only those who markedly decrease their animal protein intake may expect to benefit.

Making our urine more alkaline can also help prevent the formation of kidney stones (and even dissolve and cure uric acid stones). How can you tell the pH of your urine? See my video Testing Your Diet with Pee & Purple Cabbage.

For more on kidney stones, see How to Treat Kidney Stones with Diet and Do Vitamin C Supplements Prevent Colds but Cause Kidney Stones?. And check out my overview of kidney health in How Not to Die from Kidney Disease

Uric acid can also crystallize in our joints, but the good news is that there are natural treatments. See Gout Treatment with a Cherry on Top and Treating Gout with Cherry Juice.

Kidney stones are just one more reason that Plant Protein is Preferable

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: