Low oxalate diet handouts often fail to help people maintain the sustaining change they need to make to avoid future kidney stones.  Why? 

Skillet with vegetables being cooked

Because the handouts lead to the feeling of unreasonable constraint.  They make it difficult to eat while traveling, hard to eat at family meals, and contradict the nutrition advice people are receiving elsewhere (for example, eat whole grains!).

Sometimes, these handouts can make it seem impossible to eat well.   Keep reading to learn how different information can make it easier to manage a low oxalate diet in the real world.

What is a low oxalate diet?

A low oxalate diet reduces the amount of a chemical—oxalate– commonly found in foods by limiting certain foods.  Oxalate is an organic compound made up of two carbon atoms and four oxygen atoms.

Most people eat around 200 mg of oxalate per day without any problems.  However, some people need to limit oxalate intake to 50 mg, or 100 mg, per day to help manage a medical condition. Knowing that target level is helpful for patients.

What foods do you avoid on a low oxalate diet?

Part of the reason it is so hard to follow a low oxalate diet is that oxalate is found in many foods. For example, whole grains like buckwheat, grits, and brown rice contain oxalates; vegetables like sweet potatoes, spinach, and beets are quite high in oxalates; fruits like figs and gooseberries are also rich in oxalates; and even peanuts and lentils provide high levels of oxalates.

Whole grain cereal and strawberries

Whole Grains + Strawberries = Oxalates

Who follows a low oxalate diet?

Most often, these are people who have had calcium oxalate kidney stones several times.  Low oxalate diets are widely recommended; however, some research suggests that using other strategies should be the first line approach.  Some of these will be reviewed in the next post—stay tuned!

People who are at high risk of kidney stones because they have malabsorption—such as someone who is losing weight quickly after bariatric surgery or who has gastrointestinal diseases like Crohn’s disease—may wish to consider a low oxalate diet.  In these patients, low oxalate diets are effective at preventing kidney stones. 

More recently, there’s some research suggesting that some people with cystic fibrosis and autism have higher levels of oxalate in their blood that people without those conditions.  

They may have a form of primary hyperoxaluria—a condition where they are unable to process the molecule normally.  In general, anyone with primary hyperoxaluria should follow a low to moderate oxalate diet to stay healthy.

Occasionally, I will recommend that someone who has anemia try temporarily limiting some of the high oxalate foods at meals when they take an iron supplement.  Oxalate impairs iron absorption, so avoiding high oxalate foods like tea, coffee, and spinach when they take their iron supplement can help.

What do low oxalate diet handouts say?

Low oxalate diet handouts tend to plop commonly eaten foods into a few categories.  For example:

  • “No oxalates”
  • “Low oxalate”
  • “Moderate oxalate”
  • “High oxalate”

These four categories are broad and may or may not include the foods a client commonly eats.

In other words, they don’t list specific levels of oxalate.  For example, many handouts will include foods with 50 mg and 11 mg in the same category. 

If you are trying to eat less than 50 mg per day, it is helpful to have a sense of whether a food might have 15 mg or 45 mg.  Because you’d probably avoid the 45 mg food but maybe you’d eat the 15 mg food once or twice a week, right? 

Designing the handout with these vague categories way means food is simplified to “I can’t eat leafy greens except for lettuce.”  The handout does suggest that– because leaf lettuce is the only low oxalate green.  But when you look at specific levels of oxalates in other leafy greens, you can find kale at 2 mg per cup, mustard greens at 4 mg per cup, and collards at 10 mg per cup.  Now, bok choy and broccoli are down there at 1-2 mg per cup.

Why aren’t specific oxalate levels of foods commonly given to patients on low oxalate diets?

There’s likely two reasons.

First, there’s the assumption that people will be overwhelmed.  I don’t believe this– we nutritionists (dietitians) walk people through rather complicated schemes for managing diabetes. 

Mostly, people do just fine with numbers and some basic math.  Sometimes someone doesn’t want to, or has a limitation making it too hard to manage those approaches.  Then, they use a simpler option.

Second, the data for precise oxalate levels is a little wishy-washy.  Specific varieties of some foods can have different oxalate levels.  So, there is variation in the scientific data.  And—as happens with science—this data has changed over times.  For example, the level for strawberries has decreased.

Is there a way to empower patients to make their own decisions more easily?

Precise people many find this mentally challenging to accept these values for oxalates as reasonable approximations.  Nonetheless, I argue we need to give people the option of using this information.  We use imperfect information often (that food label data? Could be off by 5%, easily, and may actually be off by 10-15%).  

If the consequence is people avoiding healthful “Moderate” or “High” oxalate foods that have 3 mg or 11 mg per serving, we should ask ourselves:

  • Is it necessary to limit the diet this extensively?
  • Is there a way to empower patients to make their own decisions more easily?

First, for most patients, it is not necessary to limit the diet that much. In fact, there may be negative consequences to limiting the diet extensively.   Second, we can provide patients with more information easily.

This is possible because we do have reasonable, if imperfect, data. The consequences of using slightly imperfect data here are low; likely less than limiting a diet to avoid important foods like dark green vegetables, berries, and nuts for a lifetime.

Omelet over cooked collard greens
Collard greens have about 10 mg of oxalates per cup.

Caveat: Limiting one’s diet for a shorter period is occasionally important, even necessary. Always talk to your health care provider about starting and stopping special diets.

A Better Handout for Low Oxalate Diets

A low oxalate diet handout that truly empowers patients is customized.  It enables them (you) to make decisions based on the amount of oxalates in the foods they (you) eat, or provides alternatives.  It also focuses on frequency of consumption rather than categories of oxalate levels. 

I use one that has some commonly eaten foods in each category.  It also space for writing in the foods the patient normally eats. Key information:

  • food names with serving sizes
  • recommended frequency of intake (these are maximums—“up to daily” or “up to once a week”)
  • actual oxalate levels of the foods
  • patient’s individual recommended oxalate cap per day or week
  • space to note fluid intake or other secondary target.

Research suggests that clients do best if they have a few strategies to focus on rather than a long list.  If a low oxalate diet is one of them, I prefer to also offer the reminder of a second target in the same place.

Alternatives to a Low Oxalate Diet

Consistently following a low oxalate diet is challenging for some people.  If you are eating food that is prepared for you, such as meals at work, delivered hot lunches or family meals where you aren’t involved in meal planning, you may find following a low oxalate diet does not work for you.

However, particularly if you are following a low oxalate diet due to kidney stones, there are other options!  Avoiding a few simple items (coffee, tea, chocolate, and nuts) may work for you.  Read the next post to find out what questions to ask about kidney stones and nutrition.

Walnut halves in a pan

Nuts are mostly high in oxalates.

If you are following a low oxalate diet due to hyperoxaluria, it’s vital to figure out what will work for you.  This is where talking to your health care team and a registered dietitian can help get you on track with the support you need to succeed.

What You Can Do About Low Oxalate Diet Handouts

If you are on a low oxalate diet:

  • Discuss how limited you feel in your diet with your health care provider.
  • Ask for a referral to a dietitian with experience with low oxalate diets (often, these are general practice dietitian who receive referrals from urology clinics or those who work with patients with autism).
  • Watch for the next post with key questions to see if there are other nutrition concerns related to kidney stones that your health care provider can answer. 

If you provide patient care:

  • Review your handout.  Consider revising it or emailing me (stephanie.bostic@gmail.com) for permission to use mine.
  • Work specific oxalate levels of foods that patients eat regularly into your counseling.  
  • Write in specific values that are relevant to that patient.
  • Print or save the Harvard Excel Spreadsheet with oxalate levels and serving sizes for your reference. Try using the oxalate database, too.

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In Summary

  • Oxalates are found in many foods. The amounts of oxalates may vary notably between similar foods.
  • A low oxalate diet may not be best nutrition strategy for someone with kidney stones. Other people may benefit from it.
  • Information can empower people who must follow a low oxalate diet, so they can eat a wider variety of foods.

Still have questions? Get in touch!

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