This blog is part of a series discussing our integrative approach to kidney stone prevention and management. In this blog we will discuss the dietary approach to kidney stone prevention.

Kidney stone formation (also called urolithiasis or nephrolithiasis) is a complex disease influenced by multiple factors including diet, genetics, and environment. Anyone who’s experienced them can attest that stones are often very painful. When left untreated, they may contribute to more serious conditions including urinary tract obstruction and permanent kidney damage or CKD.

Read more about the etiology and prevalence of kidney stones here. 

Conventionally, the approach to treatment is a multi-pronged approach and may include medication, dietary and lifestyle interventions, surgical removal, and using ultrasonic waves to break up stone. However, dietary guidelines tend to focus on stone composition instead of on the underlying pathology. In this series, we’ve been discussing the combination of upstream risk factors that impact risk of stone formation. 

Factors that impact the integrative approach to kidney stones include:

  • Type of stone
  • Environment
  • Diet
  • Hydration and electrolyte balance
  • Microbiome and gut health
  • Genetics 

Diet is a topic that deserves a deeper dive! We’ll focus on it here today. 

Dietary Approach to Kidney Stone Prevention

The Diet Controversy and Kidney Stones

Dietary interventions are common in addressing kidney stones. The reality is, we need a more comprehensive approach when it comes to preventing kidney stone formation and kidney damage. Dietary approach to kidney stone prevention is one aspect of this comprehensive integrative approach.

First, let’s start by outlining the impact of the standard American diet (SAD), which seems to increase risk of kidney stone formation. When we use the term SAD, we are generally referring to a diet that includes:

  • Consumption of sugary beverages and soda (and high carbohydrate consumption in general)
  • Increased intake of processed/refined foods like cereals, crackers, baked goods, etc.
  • Processed, fried, conventionally raised, high-nitrate animal protein
  • Low intake of fiber and fresh produce in general
  • A “beige” diet (low in phytonutrients and antioxidants) lacking color and low in enough variety of colorful fruits and vegetables 
  • Inadequate amounts of healthy, anti-inflammatory fats, and high amounts of refined unhealthy fats

Interestingly, studies have shown that eating more fresh produce is protective from kidney stone formation. When we consider that the SAD is low in protective foods and the key nutrients found to be helpful in preventing urolithiasis. Let’s examine these factors that impact kidney stones in more detail. 

Macronutrient Balance for Kidney Stones (Protein, Fat & Carbs)

Protein

For a long time, it was assumed that stone formation was at least in large part due to excessive protein intake. As a result, those at risk for stone formation were instructed to eat a low protein diet to prevent urolithiasis. However, there are underlying factors that cause a domino effect impacting how the products of protein breakdown lead to stone formation. This includes micronutrient and electrolyte balance, metabolic disorders, digestive abnormalities, and of course dysbiosis (we’ll discuss these in detail in another blog). 

It’s true that excessive protein intake can lead to more acidic urine and increased uric acid production (a risk factor for uric stone formation). Elevated protein metabolism alone isn’t a problem in isolation, there’re other upstream factors to consider that make certain individuals more susceptible to stone formation. Furthermore, the source of protein seems to be significant. Animal protein sources seem to play a bigger significance in risk of stone recurrence, while plant-proteins might be protective.

Carbohydrates and Fiber

Though excessive consumption of carbohydrates isn’t recommended, excessive restriction of carbs in people prone to kidney stones should be avoided. We suggest avoiding sources of simple sugars, fructose and high fructose corn syrup (that includes sugar sweetened beverages, pastries, sodas, and even the so-called healthy sweetener agave). Fructose consumption in particular seems to increase production of excess uric acid and simultaneously reduces its excretion in the urine. 

Instead, we want to opt for more nutrient-dense, high-fiber, low-glycemic carbohydrates, including root vegetables, berries, whole grains and legumes. Increased consumption of fiber helps to promote improved microbiome health and diversity, which may play a significant role in kidney stone formation risk. Furthermore, there is interesting research that indicates that individuals who aren’t getting enough dietary vitamin C to meet their needs while on a low-carb diet may increase their risk for developing certain types of kidney stones.

This begs the question, what other nutrient deficiencies might contribute to stone formation when macronutrients might not be optimized?

Fats and Essential Fatty Acids

In order to balance a moderate protein and carb intake, some individuals might benefit from increasing calories from fat. Healthy fats include omega 3 sources like fish and fish oil, nuts, seeds, olive oil, and avocado. Grass-fed ghee might be especially beneficial due to a combination of anti-inflammatory profile, vitamin A, and gut healing benefits of the butyric acid component.

Independently, increased fat intake has not been associated with kidney stone formation. However, when coupled with a SAD diet full of simple carbohydrates and fried and processed foods, and excessive protein intake that seems, at least in part, to be a contributing factor. At the same time, when eating a high-fat diet as part of a ketogenic approach, excessive restriction of carbohydrates seems to contribute to stone formation in individuals with existing risk factors. In those cases, it’s recommended to work with a nutritionist to ensure that you’re balancing your macronutrients effectively to avoid kidney stones. 

Micronutrient Balance

Fat-soluble vitamins

We can’t talk about dietary approach to kidney stone prevention without discussion fat soluble vitamins. Fat soluble vitamins include vitamins A, D, E, and K. Deficiencies in D, A and K in particular have been associated with kidney stone formation. This might at least in part be due to the fact that these vitamins play a major role in calcium metabolism and bone mineralization. When D and K are deficient, calcium from diet is deposited in arteries instead of in bones, leading to calcification and stone formation. 

In fact, vitamin K depletion might be an independent risk factor for kidney stone formation. When individuals form kidney stones, a vitamin-K dependent protein (matrix Gla protein) is secreted in inactive form. This protein when activated with vitamin K can inhibit the growth of calcium oxalate crystals. When vitamin K isn’t available, more crystals may form.

To improve dietary intake of these nutrients, foods like eggs (especially the yolks), organ meats, ghee, natto (fermented soybeans), and full-fat cheeses (assuming you’re able to tolerate dairy) can be helpful to include in your diet. Daily sun exposure (at least 20 minutes a day) can also help promote increased vitamin D levels. However, supplementation is often indicated. Issues with absorbing fats and fat-soluble vitamins due to digestive issues are common, a nutritionist or a clinician trained in Integrative and Functional Medicine can help you determine if supplementation is needed. 

Oxalates

Oxalates are front and center in the dietary approach to kidney stone. In fact, calcium oxalate stones comprise most kidney stones (75%). There’s some evidence that limiting consumption of oxalates can help reduce stone formation. Food containing high levels of oxalates tend to be generally considered healthy, including spinach, beets, nuts and seeds, to name a few examples. 

What makes these foods healthy for some people, and contribute to stone formation in others?

One reason might be inadequate calcium intake from the diet. Food sources like broccoli, sardines and canned salmon, and leafy greens like kale and collard greens can be good low-oxalate, calcium-rich food sources. When consumed in adequate amounts, calcium binds to oxalates in the intestines, preventing it from being absorbed and reducing formation of stones.

Another important consideration is the composition of the microbiome. When oxalate-degrading bacteria in the gut is inadequate, it can increase risk of developing kidney stone disease. More about that in a future article.

Vitamin C

Ascorbic acid has been associated with formation of kidney stones. Excessive intake of vitamin C might increase oxalate production. Some studies have shown higher intake of vitamin C is associated with increased risk of kidney stones, but only in people predisposed to forming oxalate-stones. Regardless, caution should be used in supplementing vitamin C within the context of the larger, integrative picture. 

Phytate

Phytate, sometimes called phytic acid, is an antioxidant compound found in certain foods like beans, lentils, nuts, and seeds. Some have claim that phytate intake might prevent the absorption of certain nutrients, but actually it might be protective for kidney stone! One study found that women who consumed more phytate had reduced risk of kidney stone formation. Other studies have come to the same conclusion. This might account to the benefit of eating these particular foods, which happen to be good plant-based protein sources, in place of animal protein. 

Salt and Other Electrolytes

Calcium is a controversial topic when it comes to risk of kidney stone formation. Surprisingly, higher intake of dietary calcium (from food sources like leafy greens, salmon, and legumes, for example) is associated with lower risk of stone formation. On the other hand, taking calcium supplements may be linked with increasing risk of kidney stone formation (this might be gender specific to men). 

Furthermore, the conversation often fails to address the nuance of calcium consumption in the form of dairy, which might not be superior over plant-based forms of calcium, or to account for the impact of vitamin D deficiency. 

Magnesium is another electrolyte that is often overlooked. Magnesium is part of hundreds of the body’s biochemical reactions, so adequate intake is essential. Furthermore, ensuring adequate intake of magnesium can help prevent the formation of calcium oxalate stones by destabilizing the bond between the two compounds causing them to split. 

Food sources of magnesium include swiss chard, spinach, almonds, and pumpkin seeds. Many of those foods might be contraindicated in a low-oxalate diet, so supplementation might be indicated before gradually adding those foods back as part of a comprehensive approach. Supplementing with chelated forms of magnesium (like magnesium citrate, malate, or bisglycinate) or making time for an epsom salt bath (magnesium sulfate in the salts absorbs through the skin).

But the most important electrolyte in the dietary approach to kidney stone is sodium. Excessive sodium (salt) consumption has been associated with stone formation, particularly when fluid intake is inadequate. High sodium excretion increases calcium deficiency by increasing excretion through the urine. Reducing excessive intake of sodium, especially from processed foods like cured meats, can be helpful, along with ensuring adequate intake of potassium-rich foods like broccoli, leafy greens, squash, potatoes, mushrooms, bananas, cantaloupe, and grapefruit to name a few. 

More about the impact of electrolyte balance on kidney stone formation in a future blog.

Water (the forgotten macronutrients)

Inadequate water intake is one of the most significant contributing factors to kidney stone formation. The process of excretion of oxalate consumes salt and water, as a result dehydration is more likely. 

Taking mineral compounds containing citrate (like magnesium citrate or potassium citrate) can prevent the formation calcium oxalate and uric acid stones while balancing mineral needs. Adding lemon juice or apple cider vinegar (4oz per day) to water might also help prevent urolithiasis through the same mechanism. Your Integrative or Functional Medicine clinician can help create a plan that best fits your needs.

The Bottom Line

Multiple factors impact kidney stone formation, including dietary factors. It seems there’s no single food or food component that causes stone formation. Rather, there are likely a combination of factors including nutrient depletion, dehydration, and poor food choices combined with environmental factors, genetics, and gut integrity and microbiome balance which combined play a role.

Therefore, the integrative approach to addressing kidney stones must account for the constellation of these factors. Practitioners working with individuals to prevent kidney stone formation should formulate a personalized approach that modifies all relevant components in their integrative approach. We’ll explore these connections in future blogs in this series.