Logo_spinachThere I was, enjoying a delicious green smoothie when an article about oxalates in spinach and other leafy greens caught my attention. Is there a hidden danger lurking in my delicious, beloved green smoothie?

Oxalic acid (also referred to as oxalates) are found in many foods and are a controversial subject among nutritionists and health experts. Finding a definitive answer online regarding the potential safety or dangers of this substance can make your head spin (as most cutting-edge nutrition research will).

What Is Oxalic Acid?

Oxalic acid is a naturally occurring chemical in plants and animals and is also consumed in a variety of different foods such as leafy greens, nuts, seeds, most berries, certain fruits, soy and soy products, meat and dairy products. In large amounts, oxalic acid is poisonous, but toxic levels are not found in foods that we normally eat.

The main controversy surrounding oxalic acid in food is whether or not they contribute to the formation of kidney stones. About 80% of the kidney stones formed by adults in the U.S.A. are composed of calcium oxalate. Oxalic acid binds with other minerals such as calcium which form a salt known as an oxalate. Oxalic acid interferes with the absorption of calcium in foods because they bind with it, making it unusable by your body.

Without oxalic acid, foods such as spinach and kale would have a much higher, bio-available calcium content than they do because it is bound up with oxalic acid. These oxalates are usually passed though the urine but in vulnerable individuals, they may crystallize, forming larger stones that cause excruciating pain and require medical attention.

What Foods Contain Oxalates?

Many foods contain oxalic acid, especially leafy greens such as spinach, kale, chard, parsley, collards and beet greens. Spinach has the highest levels of oxalic acid – 750 milligrams per 100 gram serving. So, should you be concerned about the oxalate content of your spinach green smoothies?

Should You Be Concerned?

The short answer is “generally, no”. There are a few rare medical conditions such as Primary Hyperoxaluria and Enteric Hyperoxaluria where one would need to restrict their dietary intake of oxalic acid. Also, those who are susceptible and have been treated for calcium-oxalate kidney stones, and therefore at risk of forming them again, should watch their intake of oxalate-containing foods.

Otherwise, oxalic acid is not believed to be a health concern for most people. Keep in mind that your body regularly produces oxalic acid, often synthesizing other substances such as vitamin C into oxalic acid. Whether you eat foods that contain it or not, your body maintains a naturally-occurring level of oxalic acid and regularly produces it whether you consume it in your diet or not.

Health Experts Weigh In

Most mainstream diet and nutrition experts do agree that oxalic content of foods should not be a concern to healthy individuals. The nutritional benefits of eating oxalate-containing foods such as spinach outweigh the minute risk of forming kidney stones. Dietitians and nutritionists generally do not steer people away from dark, leafy greens because they contain oxalic acid.

Some raw food diet experts take the oxalate debate one step further by suggesting that oxalic acid is actually beneficial when consumed from raw, organic greens. They claim that it is the cooking of foods that contain oxalic acid which lead to problems in humans.

And then there is this article that praises the cancer-curing affects of oxalic acid.

If You Are Concerned About Oxalates

If you have a history of kidney stones or a medical condition that is complicated by the consumption of oxalate-rich foods, you should contact your doctor or health practitioner for advice. There is some helpful information on the web which lists oxalate levels of many foods which can help you plan your diet should you feel the need to reduce your intake of oxalic acid-containing foods. In general, replacing oxalate-rich greens such as spinach and kale with Romaine lettuce or other lettuces will lower exposure, but also lower overall nutrient density of your smoothies.

My Approach To Oxalates In Green Smoothies

Since I do not have Hyperoxaluria or any history of kidney stones, I am not going to worry about oxalic acid in my green smoothies. The amount I consume on a daily basis is not toxic. The research that exists does not conclusively point to oxalates as the absolute cause or even a leading contributing factor in the possible formation of kidney stones.

What I will do, however, is rotate my greens so that I am not always eating spinach, which contains the highest levels of oxalates. Simply rotating or mixing spinach with lower-level oxalate-containing foods will help even things out and lower my overall exposure. Besides, rotating greens and other foods regularly helps to limit over-consumption of any one nutrient and provides health-promoting variety in the diet.

Do not become obsessed with lowering oxalate exposure though. It’s silly to choose one green over another based on oxalic content if you do not have a preexisting medical condition that should warrant such a choice.

Also, isolating one substance in food that may or may not cause a health problem when consumed in excess is a narrow way of looking at health and nutrition. Eating a whole foods diet provides a wide spectrum of nutrients, phytochemicals, vitamins, minerals and trace elements that work together to make a perfect, whole food that nourishes the body. Your body, when given whole food and proper nutrition, works effectively to process the foods you eat, eliminate the substances it doesn’t need and protect itself against disease and other health problems.

Enjoy Your Green Smoothies!

Green smoothies have a wide range of health benefits, many of these from the potent antioxidants found in spinach, kale, chard, blueberries, strawberries, carrots, oranges, tomatoes and other foods – all of which have oxalic acid.

So go ahead and enjoy your green smoothies and the health benefits they provide!

More Information From These Sources: GrowingTaste.com / BeautifulOnRaw.com / The World’s Healthiest Foods / Wikipedia / Info on Hyperoxaluria.

Return to the Green Smoothie FAQ.


About Tracy
Tracy Russell is the creator of the Green Smoothie Health & Weight Loss Program and founder of Incredible Smoothies. She is passionate about helping people improve their health with green smoothies and a whole foods lifestyle.




Green Smoothie Health & Weight Loss Program


Sign up for our newsletter and get a free e-mail course, "7 Steps To Better Health".  Each lesson focuses on a different aspect of your overall health and includes a green smoothie recipe.

Tags: , , , ,

One Comment to “Oxalates In Spinach – Is Oxalic Acid A Green Smoothie Health Concern?”

  1. Jeffery Rollins says:

    A Registered Dietitian has approved your article. Excellent presentation of the facts as well as opinions from both pro and anti-oxalate camps.