top of page

Kidney Stones: What to Eat and Avoid

Updated: Jan 21


Dealing with kidney stones can be an excruciating experience. If you have ever had a kidney stone, you know just how painful it can be. Unfortunately, if you have had one kidney stone, there is a 30-50% chance that you may experience another one within the next five years and it's not just the pain that you have to worry about either. Researchers have found that people who suffer from kidney stones are also at a higher risk for kidney failure, osteoporosis, and cardiovascular disease. One common question that arises is whether changing the diet can effectively reduce the risk of kidney stone formation.


In this article, we will provide valuable information on why diet can play an essential role in preventing kidney stones. We will discuss a few scientifically proven dietary recommendations that can benefit individuals dealing with all types of kidney stones. While personalized recommendations based on diagnostic tests, such as stone analysis and the 24-hour urine collection test are important, following these general guidelines can serve as a helpful starting point for all stone formers.


Key Principle for kidney stones diet # 1: Stay hydrated

Drink on average 3-3.5L fluids daily to avoid kidney stones.

Drinking plenty of water can be protective. According to a study conducted by Dr. Borghi et al, there is a strong correlation between the concentration of urine and the risk of forming stones.


The kidneys filter water and salts out of blood daily and reabsorb some of it, forming urine. On average, urine output is about 1-2 liters per day. Insufficient fluid intake leads to concentrated urine with a high salt content. This can cause salts to crystallize and form stones. In chemistry, this concept is referred to as "supersaturation."


For this reason, patients are advised to increase their fluid intake. New technology, such as smart water bottles, or setting a reminder on your smart phone, can make it easier for individuals to drink more fluids, by offering reminders during the day to drink water.


According to the most recent American Urological Association Guidelines, stone formers are advised to aim for"fluid intake that will achieve a urine volume of at least 2.5 liters daily". Fluid intake of around 3000-3500 ccs (12-15 cups) per day is recommended, but it can vary depending on different factors.


It is important to note that certain medical conditions, such as congestive heart failure (CHF), may require limitations on fluid intake. It is always recommended to consult with your health care provider to determine if this recommendation is safe for you.


Key Principle for kidney stones diet # 2: Don't avoid calcium

Foods high in calcium.

The concept of increasing calcium intake to reduce the formation of renal calculi can be confusing. This is because most kinds of kidney stones actually contain calcium, the most common being calcium oxalate stones or calcium phosphate stones. However, the mechanism behind this is related to the absorption of oxalate, also known as oxalic acid, which is a naturally occurring compound in plants. We find oxalate in food and our bodies make them as well. When our diet lacks sufficient calcium, our bodies absorb a higher percentage of oxalate from the gut, which leads to increased excretion of calcium oxalate and ultimately to the formation of more kidney stones.


So, the general recommendation to prevent kidney stones is to maintain a normal calcium intake of approximately 1000 - 1200 mg calcium per day. It is best to get calcium from food sources, such as dairy products which are a good source of calcium. You may want to check the Nutrition Facts label to find out the calcium content of different beverages and foods. If you do not consume milk or yogurt, discuss calcium supplements or pills with your healthcare provider.


The International Osteoporosis Foundation offers an online calculator to help you determine your daily calcium intake if you're unsure whether you meet the recommended amount of 1000-1200 mg per day.


Key Principle for kidney stones diet # 3: Limit salt intake

salt

Avoiding a high sodium diet is important to keep your blood pressure under control, and can also lower the risk of stone formation. Too much salt intake surprisingly leads to an increase in calcium levels in your urine. This is because your kidneys will try to eliminate the surplus of salt, and calcium is excreted along with it.


Higher calcium levels in the urine may lead to formation of stones and to bone mineral loss. This explains why many individuals who are prone to forming stones are also at risk of developing bone disease. Therefore, reducing salt intake is crucial in preventing the formation of kidney stones but also in preventing bone loss.


Achieving a low salt diet is challenging in the real world, but is definitely possible as proven by researchers from the University of Parma in Italy. In their study, reducing sodium intake over a prolonged period of time significantly improved the excess calcium in the urine of patients with calcium stone disease, which is the most common type of stone. A low-salt diet, achieved by not adding salt to food and by reducing high-salt content foods, normalized urine calcium levels in a substantial proportion of the cases they studied (about 30%).


Key Principle for kidney stones diet # 4: Eat your fruits and veggies

Fruits and vegetables.

Plant based foods are known to lower the risk for kidney stones. They typically contain an abundance of potassium alkali which helps to lower urine levels of calcium. Fruits and vegetables also contain citrate, or citric acid, which is recognized for its antioxidant properties and its ability to prevent stone formation. When citrate is excreted in the urine, it binds to calcium, preventing it from binding with oxalates, thus preventing the formation of renal calculi.


Research studies have demonstrated that a diet high in potassium can help protect against the formation of new kidney stones. While green vegetables do contain higher levels of oxalate, overall, plants have a net protective effect and are an important component of a kidney stone diet. On the other hand, foods of animal origin also contain potassium, but the acid production from these proteins often contribute to an acid load in the body, and may increase the risk of developing renal calculi.


Another possible explanation why a plant based diet may be beneficial, comes from a study published in CJASN in 2016, which found that individuals with a higher potassium intake, besides having a more alkaline urine, tend to also have larger urine volumes. This is because fruits and vegetables have a high water content. This results in a more dilute urine thus lower risk for precipitating crystals to form calculi.


Key Principle for kidney stones diet # 5: Healthy microbiota may help prevent kidney stones

Microbiota consists of all the microbes living in the human gut.

The role of gut microbiota in renal calculi formation, is an area of growing interest. The human gut microbiota consists of all the microbes, like bacteria, living in the human gut. While most microbes in the body are helpful, they can become harmful when out of balance.


There is strong evidence that the gut microbiota plays a major role in human health. According to research, individuals affected by kidney stones have distinct differences in their gut microbiota compared to those without stones. Specifically, they have fewer strains of bacteria that degrade oxalate and produce short-chain fatty acids and this may result in predisposition to forming renal calculi.


This new understanding of the role of microbiota opens up new possibilities for preventing recurrent kidney stones such as dietary interventions to stimulate the growth of healthy bacteria in our gut and potential therapeutic approaches which may include the use of probiotics and even microbiota transplantation. More research is needed to support this recommendation.


Conclusion

Making a few dietary changes can effectively support your kidney health and reduce your risk of forming renal calculi. Here are the main takeaway points:

  1. Extra water helps with any type of kidney stone. Drinking on average 3-3.5 liters (12-15 cups) of fluids per day is recommended, if not otherwise contraindicated. Avoid sugary drinks and soft drinks!

  2. Boost your health with calcium-rich foods! Calcium is important for maintaining strong bones and can also help with kidney stone prevention. To prevent stones, 1000-1200 mg of calcium per day is recommended.

  3. A low-sodium diet requires significant effort and lifestyle adjustments but is a good plan for stone prevention. Keep in mind that even small changes matter in the long run to prevent renal calculi.

  4. Eating fruits and vegetables (high in potassium and citrate) lowers the risk of kidney stones and supports kidney health. Please be advised that some patients with advanced kidney disease may not tolerate high potassium in their diets. Talk to your doctor if you have questions about this recommendation and how it applies to your case.

  5. Adding more fiber to your diet and consuming fermented foods like kefir, yogurt, and kombucha tea can potentially support a healthy gut microbiota and may prevent the formation of renal calculi. Please note that some fermented foods, such as sauerkraut, may have high salt content and this is not advised.

Additional resources:

The University of Chicago website offers comprehensive information on kidney stones dedicated to patients, doctors, and scientists, provided by Dr Fredric Coe and his colleagues. Their blog is an invaluable resource for all those interested in learning more on this topic.


The International Osteoporosis Foundation offers an online calculator to help you determine your daily calcium intake if you're unsure whether you meet the recommended amount of 1000-1200 mg per day. Their website also provides the calcium recommendations per age groups and a list of calcium content of common foods which can be a very helpful information.


266 views0 comments
bottom of page