January 24, 2023

Kidney Stones and Oxalate Foods: What You Need to Know

Table of Contents

Kidney stones, specifically calcium oxalate stones, can be an incredibly unpleasant experience. If you’re here because you suffer from frequent kidney stones, I first want you to know that there are things you CAN do to help prevent their formation or frequency of occurrence. In this blog we will discuss oxalate foods, calcium, supplements, fluid and sodium.

 

You can help your body to avoid forming kidney stones by understanding oxalate foods. Contrary to popular belief, you do NOT need to avoid all foods that contain oxalate. Complete avoidance of oxalate foods is actually not necessary. The key is for you to avoid ultra high oxalate foods. We will get into it here in a second, but first let’s cover the basics. 

 

What is Oxalate? 

 

Oxalate is a chemical compound found in some foods. Oxalate binds with calcium, which can form tiny crystals in the kidneys. Over time, these crystals can form stones that can cause pain, nausea, and really make your life miserable until they pass or are surgically removed. 

 

If we were to outline all the foods that contain oxalate, you’ll probably feel overwhelmed by the potential long list of foods you should be aware of. But do not fret, my friend! The thing about oxalate content is that there are foods that have low, medium, high, and super high levels of oxalate. Studies have shown that often avoiding the super high oxalate foods is enough to prevent oxalate kidney stones [1]. 

 

Let me demonstrate the real jump certain oxalate foods might have so that you get my point about super high oxalate foods. For example, ½ cup of yams or turnips are considered high oxalate foods (40 mg and 30 mg, respectively), but ½ cup of cooked spinach contains 755 mg of oxalate and 1 cup raw of spinach has 656 mg of oxalate. 

 

For this reason, when starting to avoid oxalate foods, it would be a good idea to start with the super high oxalate foods as this might be enough to make a BIG difference in your oxalate intake.  

 

There is a general recommendation for your oxalate intake to be around 100 mg per day [2]. But again, if you limit those super high oxalate foods from your diet, this might make a big enough difference that you may not need to count mg of oxalate. 

 

Oxalate Foods by Very High, High, Moderate, and Low.

 

Some of the most common high oxalate foods include nuts, spinach, soy products, rhubarb, beets, and chocolate. You might be tempted to avoid all these foods but let us look a little closer at how much oxalate some of these foods contain.

Bowl of raw spinach high oxalate foods

Very High Oxalate Foods

 

  • Spinach ½ cup cooked — 755 mg
  • Spinach 1 cup raw — 656 mg
  • Rhubarb ½ cup — 541 mg
  • Buckwheat groats 1 cup cooked — 133 mg 
  • Almonds ¼ cup — 122 mg
  • Miso soup 1 cup — 111 mg

 

High – Moderate Oxalate Foods

 

  • Potato baked with skin 1 unit — 97 mg
  • Navy beans ½ cup — 76 mg
  • Beets ½ cup — 76 mg
  • Cashews ¼ cup — 49 mg
  • Raspberries 1 cup — 48 mg
  • Peanuts ¼ cup — 27 mg
  • Dried Figs 5 units — 24 mg
  • Kidney beans ½ cup — 15 mg

 

Low Oxalate Foods

 

  • Carrots ½ cup cooked — 7 mg
  • Corn chips 1 cup — 7 mg
  • Popcorn 1 cup — 5 mg
  • Pumpkin seeds ¼ cup — 5 mg
  • Mustard greens 1 cup raw — 4 mg
  • Bananas 1 unit — 3 mg
  • Milk 1 cup — 1 mg

 

If you’re at risk for kidney stones, it’s best to take into consideration the high oxalate foods in your diet and replace them with a lower oxalate food. Substitutions are available and easy to implement!

 

Oxalate Foods and Calcium

 

It’s also important to eat a balanced diet (which I can help with, btw) and get enough calcium. It is a very common misconception that forming calcium oxalate stones means that you should avoid calcium. 

 

This is actually quite the opposite of what is recommended. Calcium in the diet helps bind with oxalate in the gut and prevents it from being absorbed into the bloodstream [3, 4]. This can be a HUGE help to prevent oxalate stones from forming. 

 

Can you just take calcium supplements and see the same benefit? Actually, no [5]. The process of calcium binding to oxalate happens during digestion, therefore eating these calcium-rich foods is what makes this process work. 

A glass jar of milk and a vase of flowers, oxalate foods

Calcium-Rich Foods

 

  • Cow’s Milk 2% 1 cup — 309 mg calcium
  • Mozzarella Cheese ¼ cup — 149 mg calcium
  • Greek Yogurt non-fat 1 container (156 grams) — 111 mg calcium
  • Cottage Cheese ½ cup — 88 mg calcium

 

It is also massively important to understand that there is a connection between stone forming predisposition and bone mineral loss [6]. So in a sense, the recommendation to increase calcium intake is two-fold. Firstly, it binds to oxalate and leads it away from the bloodstream. And second, it aids in the protection of bone mineral loss overtime. 

 

How much Calcium do I need to consume? 

 

It is generally recommended for adults to consume between 1000 mg to 1200 mg of calcium per day [7]. This may vary a little depending on your age, past medical history, and if you are still menstruating or not.  

 

Supplements

As mentioned above, supplementation of calcium does not seem to work as well as eating calcium-rich foods. We recommend sticking to foods on this one. 

 

High doses of Vitamin C supplementation has been linked to an increase of kidney stone formation. We do not recommend consuming more than 1000 mg per day of vitamin C as it may increase your risk of kidney stones [8].

 

Fluid

 

Hydration is a really important aspect of kidney stone prevention. The kidney foundation recommends that individuals drink 2.5 L per day in order to produce good urine volume [8].

 

Over the course of my career, I have heard urologists recommend anywhere from 2 to 3 L per day in order to prevent kidney stone formation.

 

If we think about it, it makes sense! We need to be properly hydrated in order to excrete and remove particles from our bodies. Removing these particles will prevent them from hanging out in our bodies, getting fused to other elements, and forming kidney stones. 

 

Fluid intake is massively important and another reason why drinking water is part of nutrition self-care. If you’re curious, we have a quiz to see if you’re dehydrated!

 

Sodium

 

I think this part of oxalate kidney stone prevention surprises a lot of people. So why is a low sodium diet important here? 

 

A high sodium diet is associated with increased calcium in the urine. This is not good news. Unfortunately, people that are prone to forming kidney stones are also fairly sensitive to the amount of sodium consumed and how their calcium responds to it [9]. 

 

Calcium will follow sodium and in turn, an increased calcium amount will be excreted through the urine. This is bad news. We absorb sodium very well from the diet. We do not absorb calcium from the diet very well, which means that the calcium being excreted is coming from our bones [9]. 

 

A low sodium diet is also important to maintain good blood pressure which is controlled by the kidneys. Essentially, too much salt is just not good for your kidneys in general. 

 

Who is at risk of developing Kidney Stones?

 

Honest answer here, anyone can be at risk of forming kidney stones. I will say, however, certain people are more prone to developing them compared to others. This includes those who have a family history of kidney stones, those with conditions such as gout or Irritable Bowel Disease (Crohn’s disease or Ulcerative Colitis), and those who don’t drink enough fluids. 

 

People who take certain medications, such as diuretics, can also be at an increased risk. It’s important to speak to your doctor if you think you may be at risk for developing kidney stones. 

 

How are kidney stones treated? 

 

The interventions for these very unpleasant small stones can vary widely on their size and type of stone. In some cases, a doctor may recommend drinking plenty of fluids and taking certain medications to help pass the stone. 

 

In other cases, a procedure such as shock wave lithotripsy or a ureteroscopy may be necessary. This involves using a device to break up the stone into smaller pieces so they can be more easily passed. In severe cases, surgery may be necessary to remove the stone. 

 

It’s important to speak to your doctor to determine the best treatment plan for your specific situation. 

 

Benefits of Meeting with a Dietitian

 

Want some more tailored advice to help you navigate the best diet for YOU? Enter our wonderful profession! Making an appointment with a dietitian can be a great way to reduce your risk of developing kidney stones. 

A dietitian can help you develop a personalized diet plan that is tailored to YOUR individual needs. We can provide guidance on which foods to avoid, such as high oxalate foods, and which foods to include, such as calcium-rich foods. 

 

We can also provide advice on how to stay hydrated, which can be a little tricky if you’re not used to drinking 3 liters per day. 

Cat and Kelly Registered Dietitians

Frequently Asked Questions

 

  • Do energy drinks cause kidney stones?

Energy drinks have not been proven to cause kidney stones. However, the sugar in energy drinks can be pretty high, which is not recommended for kidney health. Energy drinks also have a high caffeine content and caffeine in general is a diuretic. If you are prone to forming kidney stones, it is recommended that you drink water as it is more hydrating and it does not contain sugar. 

 

  • Can stress cause kidney stones?

Stress can indirectly affect factors that may aid in kidney stone formation. An individual experiencing high levels of stress is more likely to be dehydrated, have a poor diet, consume too much caffeine, and be less physically active. All of these factors may contribute to an environment within the body that is more susceptible to kidney stone formation.

 

  • What is Oxalate Dumping? 

Oxalate dumping is a theory that a high oxalate diet may cause rapid oxalate excretion through the kidneys, which may lead to kidney stone formation. This theory, however, is not scientifically proven nor has it been demonstrated in individuals who consume a high oxalate diet. 

 

  • Chocolate and Oxalate Kidney Stones

I am a huge chocolate fan, and I stand by the fact that it can be a wonderful source of antioxidants! Chocolate oxalate content varies widely. Hot chocolate that is homemade may contain up to 65 mg of oxalate per 1 cup, while one chocolate chip cookie may contain 10 mg oxalate. 

I think it is better to think about portions when it comes to chocolate. If we think about it, the sugar in some of the chocolate treats might be just as a big concern as the oxalate content [2]. 

So instead of avoiding all things chocolate, I’d recommend having a reasonable portion with dairy in order to aid in the excretion of oxalate. Milk and chocolate make a wonderful pair! 

 

Conclusion 

So let’s sum all of this up real nice for you. If you are someone who frequently forms oxalate kidney stones, here is what you need to do:

  • Avoid High Oxalate Foods

  • Get enough calcium via your diet

  • Skip the calcium supplement

  • Skip the vitamin C supplement

  • Get plenty of fluids on a daily basis

  • Avoid high sodium foods

 

If this feels massively overwhelming, consider working with a dietitian. We can help you find your way to a healthy diet armed with all the tools to prevent you from forming oxalate kidney stones!

 

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I am a Registered Dietitian (RD) based in Chicago, IL. I have worked in various clinical settings including dialysis, ICU, and NICU. I am bilingual and love my Spanglish speaking peeps!