How High Oxalate Foods Cause Kidney Stones – Experts Explain

We have often been told that green leafy vegetables are good for our health. While this is true, an excess of certain vegetables may lead to the formation of kidney stones. However, not just vegetables but other foods rich in oxalates can also cause kidney stone formation. If you want to know how high oxalate levels in foods are linked to kidney stones, this article will help you understand all about it.

To get a better understanding of this, we reached out to our experts Edwina Raj, Head of Services – Clinical Nutrition and Dietetics, Aster CMI Hospital, Bangalore, Dr Shashank MS, Consultant – Urology and Renal Transplant, Aster CMI Hospital, Bangalore and Dr Kapil Jain, Sr Consultant- Urology, RG Hospitals, New Delhi. Read ahead.

How Oxalate-rich Foods Lead To Kidney Stones

Before we start telling you how oxalate-rich foods are linked to kidney stones, let us explain what oxalates are. As per a 2023 PubMed study, published at MDPI’s Foods Journal, oxalates (or oxalic acid) are natural compounds present in many plant-based foods such as leafy greens, nuts, seeds, and cocoa. They are generally considered harmless, but they can bind to calcium in the kidneys and form calcium oxalate crystals. This is a major cause of kidney stones for sensitive individuals. 

Shedding more light on this, Edwina shares, “High-oxalate foods can contribute to kidney stones because oxalate is a natural substance that can combine with calcium in the urine and form crystals in the kidneys. When a person regularly eats large amounts of foods that are high in oxalate, the level in the urine may increase, which raises the chance of these crystals forming.” 

“Over time, these small crystals can join and grow into kidney stones. Dieticians explain that this risk becomes higher when people do not drink enough water, because concentrated urine makes it easier for crystals to form. Eating a balanced diet, drinking enough fluids, and not consuming excessive amounts of high-oxalate foods can help reduce the risk of kidney stone formation and support better kidney health,” adds the expert.

Signs Of High Oxalates In The Body 

Kidney stones are generally the first symptom that the oxalate level in your body is high. However, not everyone with hyperoxaluria (it is a condition that occurs when oxalate levels in your urine are high) has kidney stones. As per the Cleveland Clinic, some other signs of hyperoxaluria consist of:

• Blood in urine.
• Recurrent Urinary Tract Infections (UTIs).
• Failure to Thrive as an infant (FTT) or growth-altering.

Explaining this further, Edwina says, “The first signs of high oxalates in the body are often related to the urinary system. This is because excess oxalate can combine with calcium and start forming small crystals in the kidneys.” On this note, Dr Jain lists some symptoms:

• Flank or lower back pain.
• Painful or burning urination.
• Blood in the urine.
• Frequent urge to urinate.
• Nausea and vomiting during a kidney stone episode.
• In some cases, recurrent urinary tract infections may also be associated with kidney stones.

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Tips To Flush Out Oxalates From The Body 

According to Harvard Health, foods which can help flush out oxalates include yoghurt, soy products, beans, lentils and seeds. Citrate, which is a salt of citric acid, binds to calcium and aids in blocking stone formation. The report stated that studies have shown that consuming 1/2 cup of lemon juice concentrate, diluted in water each day (or the juice of two lemons), can increase urine citrate and likely reduce kidney stone risk.

To help flush out oxalates from the body and lower oxalate levels in the urine, Dr Jain suggests a few simple lifestyle and diet changes: 

• Increase fluid intake: Drinking adequate water helps dilute urine and reduces the concentration of oxalates, lowering the risk of crystal formation.
• Maintain adequate dietary calcium: Consuming calcium-rich foods in moderation with meals can help bind oxalates in the gut, preventing their absorption into the bloodstream.
• Limit high-oxalate foods: Reducing intake of foods such as spinach, beetroot, nuts, chocolate, and tea can help control oxalate levels.
• Moderate salt and animal protein intake: High sodium and excessive animal protein can increase calcium excretion in urine, which may contribute to stone formation.
• Add probioticsto diet: Another dietary hack is combining ragi with curd; this is because some studies claim that probiotics in curd slash gut oxalate absorption by 20%.

Which Foods Flush Out Oxalate Kidney Stones Fast?

Can certain foods help dissolve kidney stones? Our expert explains. Dr Shashank MS shares, “Calcium oxalate kidney stones usually do not dissolve quickly with foods or drinks, and there is no simple home remedy that can break them down fast. Urologists explain that drinking plenty of water is important because it increases urine flow and may help small stones pass naturally through the urinary tract.” The expert lists down some foods that can help flush out kidney stones (to a certain extent):

• Citrus fruits such as lemons and oranges contain citrate, a natural substance that can help prevent certain kidney stones from forming or getting bigger. Drinking lemon water regularly may also increase citrate levels in urine, which can reduce stone formation.
• Fruits and vegetables that contain high water content, such as cucumber and watermelon, can help keep the body hydrated and support urine flow.
• Whole grains and balanced meals with moderate calcium intake may also help maintain a healthy mineral balance. 

He adds, “In some cases, doctors may suggest medications that help relax the urinary tract, so the stone can move out more easily. However, if the stone is large or causing severe pain, medical procedures may be needed to break or remove it. These treatments can include methods that use sound waves or small instruments to break the stone into smaller pieces. Early medical advice and proper hydration are important to manage calcium oxalate kidney stones safely.”

What Are The Worst Foods To Eat For Kidney Stones?

According to a report by Harvard Health, a high-sodium diet can trigger kidney stones. This is because it raises the amount of calcium in your urine. They note that it is advisable to limit total daily sodium intake to 2,300 milligrams (mg). The report further mentioned that consuming too much animal protein, such as meat, eggs, and seafood, may increase the risk of forming stones. If you're prone to kidney stones, then it is better to limit your daily meat intake, it says.

As per the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), those who have calcium oxalate stones, they should limit the following foods:

• Nuts and nut products.
• Peanuts (legumes, not nuts, which are high in oxalate).
• Rhubarb.
• Spinach.
• Wheat bran.
• Beef, chicken, and pork, especially organ meats.
• Eggs.
• Fish and shellfish.
• Milk, cheese, and other dairy products.

Now, let us understand this from an expert point of view. Dr Shashank says, “People with kidney stones should be careful about foods that can increase the buildup of minerals in the urine. Limit foods that are very high in oxalates, such as spinach, beetroot, nuts, chocolate, and certain seeds, because oxalates can combine with calcium and form kidney stones. Foods that contain too much salt, such as packaged snacks, fast food, and processed meals, should also be avoided because high sodium can increase calcium levels in the urine. Eating large amounts of red meat and other high-protein animal foods may raise uric acid levels, which can also lead to stone formation. Sugary drinks and highly processed foods may further increase the risk. A balanced diet with moderate portions and plenty of water can help reduce kidney stone risk.”

When To Visit A Dietician For Kidney Stones?

If you have kidney stones, you may need to follow a special diet plan. A professional should be consulted for this. As per the National Kidney Foundation, a healthcare professional will run blood and urine tests to understand what kind of risk factors you may have. Then the expert will suggest diet changes and medical treatment you need to prevent kidney stones from coming back. A registered kidney dietitian can guide you to make the right and necessary changes in your diet plan and lifestyle.

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The Final Word

Foods which are high in oxalate (such as spinach, beetroot and nuts, among others) can increase one’s risk of getting kidney stones. This is because oxalate is a natural substance that can combine with calcium in the urine and form crystals in the kidneys. Thus, it is advised to follow a balanced diet and drink plenty of water to keep oxalate levels in check.