Is a Low Oxalate Diet Necessary? (2024)

So, you had a kidney stone and were given some information about a low oxalate diet. Or, you found out you have oxalate kidney stones. The obvious next step is to cut back how much oxalate you eat? Right?

NOT SO FAST! Nutrition (and your bodies) aren’t that simple. The amount of oxalate in your urine, and MORE importantly, nutrition to prevent kidney stones, is MUCH more than oxalate. In fact, a strict low oxalate diet could make kidney stones MORE likely.

Let’s dive in.

What Is Oxalate?

Firstly, what is oxalate itself? Oxalate is something called a “non-nutrient”. Basically, it is a compound found in many (healthy!) foods that doesn’t provide our bodies something they need. Compare this with a “nutrient” (such as potassium, calcium or a vitamin), which does something good for our body.

Oxalate is primarily found in plant foods. Vegetables, fruits, beans, nuts, seeds and whole grains are most known for having high oxalate levels. Of course, some plant foods have more oxalate in them than others. Oxalate tends to be in very healthy foods!

Oxalate and Kidney Stones

Oxalate is probably most known for it’s role in kidney stones. This makes sense, as about 80% of kidney stones are made of calcium and oxalate. (1)

Calcium oxalate kidney stones are more likely to form with the conditions in your urine are just right. Calcium and oxalate love to bind when:

• There is a lot of calcium in your urine
• There is a lot of oxalate in your urine
• Your urine is very concentrated (aka – you don’t drink enough water!)
• There is too much acid in your urine (pH is too low)
• There is not enough citrate in your urine

Nutrition can play an important role in preventing calcium oxalate kidney stones by modifying each of these urine risk factors.

Beyond Calcium Oxalate Kidney Stones

Although a majority of kidney stones are made from calcium and oxalate, there are many kinds of kidney stones. Most notably, calcium phosphate and uric acid kidney stones are common. (1)

If you have had kidney stones that are NOT calcium oxalate, chances are you do not need to avoid how much oxalate you eat. Avoiding oxalate will not reduce your risk of kidney stones.

If you were not able to have your kidney stone analyzed, a 24-hour urine test will help you and your doctor understand what kind of kidney stone you are prone to making. And, how high your risk is for forming another stone. A 24-hour urine test will tell you exactly what YOUR risk factors are for forming another stone. You, your doctor and dietitian can use that information to come up with an effective stone prevention plan.

Does a Low Oxalate Diet Reduce Calcium Oxalate Kidney Stones?

Surprisingly, no published studies have shown a reduced risk of kidney stones by reduced dietary oxalate. Although we do know that eating more oxalate increases the amount of oxalate in your urine, this only accounts of 30-50% of the variation in urine oxalate.(2) And, many other factors play into kidney stone risk including urine calcium, pH and citrate.

In fact, the DASH diet has been well documented to both reduce the risk of kidney stones and kidney stone risk factors. (3)(4)(5)(6) The DASH diet includes 9-10 servings of fruits and vegetables per day and encourages nuts and seeds – making it fairly high in oxalate. Despite this, people who follow dietary patterns similar to the DASH diet are less likely to have kidney stones. This is likely because the DASH diet impacts many other beneficial kidney stone risk factors such as urine pH, citrate and dairy.

In fact, a low oxalate diet could make kidney stones worse in many ways.

So, what is a person with kidney stones to do!? The answer lies in kidney stone urine risk factors. Not everyone, even everyone with the same type of kidney stone, has the same urine risk factors.

Individualized Healthy Eating for Kidney Stones: Much More Than a Low Oxalate Diet

To be as effective as possible, healthy eating for kidney stones must be individualized to urine risk factors. Here is a list of common urine kidney stone risk factors. Each of these can be identified with a 24-hour urine test:

• High urine calcium
• High or low urine pH
• Low urine citrate
• Low urine volume
• High urine oxalate

Each of these urine risk factors can be targeted with specific dietary change.

Interestingly, the most common urine risk factor for kidney stones is high urine calcium. Too much salt, protein and added sugar can contribute to high urine calcium.

If you do not have high urine oxalate, then a low oxalate diet will do NOTHING to reduce your risk of stones. Instead, you should focus on your urine risk factors for kidney stones. Even if your urine oxalate is high, chances are there are much better ways to reduce urine oxalate than a strict low oxalate diet. More below!

Inaccurate Kidney Stone Nutrition Info is Rampant

Unfortunately, generic “kidney stone diet” education materials are often given to everyone with kidney stones, no matter what kind of kidney stone they have. Or, what their specific urine risk factors are. In fact, a 2018 study found that information given to people with kidney stones in the Emergency Room may be a common source of misinformation.(7) It is important to follow-up with your doctor and do a 24-hour urine test to understand what healthy eating for kidney stones should be for you.

I help people approach make personalized changes to their diet for kidney stone prevention in Kidney Stone Nutrition School.

How to Lower Urine Oxalate

If you do have high urine oxalate, then nutrition can play a very important role in lowering it. But, how much oxalate you eat is honestly not the most important piece. Oxalate balance has much more to do with how much oxalate is absorbed from your intestines, and how much oxalate your liver makes. YEP! Your liver can MAKE oxalate. Here are 3 steps to lower how much oxalate is in your urine.

Step 1: Get Enough Calcium

For most people, eating enough calcium is the most important thing you can do to bring urine oxalate down to healthy levels.

Calcium and oxalate love to bind with each other. If you eat calcium-rich foods with your meals, calcium will bind with oxalate in your intestine, stopping the oxalate from getting absorbed.

Research has shown that eating enough calcium is more effective at lowering urine oxalate than a low oxalate diet.(8)

For most adults, a goal of 1,000 – 1,200mg of calcium per day is ideal to prevent kidney stones. This is the same amount of calcium that is recommended to the general population.(9)

Eating 3 servings of dairy per day will nearly guarantee that you meet this calcium goal.

More about the best sources of calcium for kidney stones.

Step 2: Eat the Right Amount of Protein

Our liver can make oxalate from protein. So, eating too much protein can increase how much oxalate your liver makes, causing an increase in urine oxalate.(10)

Protein needs are different for everyone. But, a goal of about 0.8 grams of protein per kilogram body weight is a good place to start. This is plenty of protein for most people and is the recommended amount for healthy adults in the United States.(11)

For most of us, meat, chicken, fish and seafood are the main source of protein in our diets. Focus on limiting portion sizes of these foods to 3-6oz. And, limiting these foods to no more than 1-2 meals per day.

More about protein and kidney stones.

Step 3: Avoid Supplements

Yep! I see people forming kidney stones from supplements ALL the time.

Supplements with a Potentially MEGA Dose of Oxalate

Some supplements are made from foods or spices incredibly high in oxalate. Although these FOODS are 100% ok to eat, consuming them in supplemental form is essentially a SUPER dose of oxalate. And, you aren’t getting the other benefits of actually EATING that food itself.

The most common supplements I see that are potentially giving a mega-dose of oxalate are:

• Turmeric/curcumin
• Cinnamon
• Green “superfood” powders

Supplements Your Liver Can Easily Make Oxalate From

The other category of supplements to avoid is those that your liver can make oxalate from. Remember, how much oxalate you eat is only a (relatively tiny) piece of the story. Your liver can (and does) make quite a bit of oxalate each day. Even if you ate a completely oxalate free diet, you would still have some oxalate in your urine.

If you are eating a lot of things that your liver can convert to oxalate, this could be the REAL reason driving your high urine oxalate.

The most common supplements I see that could increase liver production of oxalate are:

• Vitamin C (or ascorbic acid) supplements
• Protein supplements (read more here) – and collagen supplements, specifically

Learn more about supplements and oxalate.

Step 4: Avoid Large Amounts of Very High Oxalate Foods

The last step to lowering urine oxalate is evaluating your diet for possible VERY large doses of oxalate. I’m not talking about almonds a few times a week or a spinach salad once in awhile. I mean consuming a TON of incredibly high oxalate foods. Think: spinach smoothies, a ton of almond flour products or rhubarb daily – especially in a diet without enough calcium.

The good news is that many people can bring their urine oxalate levels down to a safe range by simply getting in enough calcium!

The very high oxalate foods are:

• Spinach
• Beets
• Almonds (and almond products such as almond milk, flour and butter)
• Navy Beans
• Rhubarb
• Miso

If your urine oxalate levels are still high after avoiding these foods and getting in your calcium, I recommend taking stock of your diet and identifying other higher sources of oxalate you might over eating. I do NOT advocate an “all or nothing” approach. If you focus on avoiding oxalate as much as possible, you will inevitably limit otherwise very healthy foods, making it difficult to give your body the fiber, fruit, vegetable and other nutrients it needs. Ironically, a very low oxalate diet could actually HARM your kidney stone prevention efforts. It could also increase risk of other health conditions like heart disease, cancer, diabetes and even cognitive decline.

Here is a list of many foods and their oxalate amount.

Incorrect Oxalate Food Lists

You might notice that this high oxalate food list contradicts others you’ve found online. Or, even lists that your doctor gave you. Unfortunately, there is a ton of incorrect information out there when it comes to high vs. low oxalate foods. Oxalate is notoriously difficult to measure, and many of the food studies measured it incorrectly in the past. In addition, one person’s definition of a “high” oxalate food may be different than someone else’s definition.

I recommend using the Harvard Oxalate Food List, as we know the way oxalate was measured for this list was accurate. I also find it useful to stick with one list to avoid the frustration and confusion of trying to piece together other lists with conflicting information.

Plus, I HIGHLY recommend NOT counting how much oxalate you eat in the first place. This is both impossible to do accurately, and 100% unnecessary.

Low Oxalate Diet and Chronic Kidney Disease

There is some interesting research examining the role oxalate may have in kidney disease. In some cases, high urine oxalate has been linked to increased inflammation and faster progression of kidney disease. (12) In addition, “juicing” and “cleanses” that recommend extremely high amounts of high oxalate foods have been found to cause nephropathy. (13) (14)

However, not all bodies handle oxalate the same way. Some people absorb a lot of oxalate from their food, whereas others do not. Remember that diet oxalate may not even be the biggest contributor to urine oxalate. Oxalate make in the liver can be a big contributor to total body oxalate.

Because oxalate is in so many foods that we know are good for kidney disease, I do not recommend that everyone with kidney disease avoid oxalate. We know that vegetarian diets high in very high oxalate foods such as beans, nuts, seeds, lentils and vegetables can slow the progression of kidney disease.(15)

However, if a 24-hour urine test shows high levels of oxalate in your urine, it may make sense to reduce how much oxalate you eat. Work with your doctor or dietitian to figure out what is best for you!

Oxalate and Polycystic Kidney Disease

People who have Polycystic Kidney Disease (PKD) are at high risk of kidney stones.(14) And, in animal models, calcium oxalate crystals have been shown to be harmful in PKD.(16)

However, even among people who have PKD, there are differences in how much oxalate gets absorbed. The best way to know what is best for you is to get a 24-hour urine test. This will assess how much oxalate is in your urine. If urine oxalate is high, working on getting in enough calcium, avoiding large amounts of protein and reducing how much oxalate you eat may help reduce risk of kidney stones and progression of PKD.

Other Low Oxalate Diet Conditions

There are claims that a low oxalate diet helps with many different conditions. However, there has been very little research to determine if changing how much oxalate you eat impacts any of these conditions. Therefore, I cannot recommend a low oxalate diet for any of these conditions. In fact, unnecessarily avoiding oxalate could result in a diet pattern that is less healthy and lacking in important nutrients, exacerbating some of these conditions.

• Vulvodynia (17)
• Interstitial Cystitis
• Fibromyalgia
• Inflammatory Bowel Disease
• Cystic Fibrosis
• Arthritis and joint pain
• Autism
• Fatigue
• Other Autoimmune Conditions
• Other Inflammatory Conditions

As always, work with a Registered Dietitian who knows your medical history to figure out what is best for you! Ideally, find a dietitian well versed in kidney stone nutrition. I help people prevent kidney stones with a personalized approach every day in Kidney Stone Nutrition School!

Happy Eating!

Melanie