top of page

Everything You Need To Know About Oxalates In Plant Foods

Oxalates (collectively dubbed oxalic acid) are naturally occurring compounds in certain plant foods that can bind to the calcium in the body as the digestive system processes them. When oxalate binds to calcium in the stomach and intestines and it will leave the body in the stool as solid waste.

The purpose of oxalates in plants is to get rid of the excess calcium in their systems by binding to it. And that’s great if you’re a plant. But when it comes to human health, calcium oxalate monohydrates seem to be harmful.

When a person consumes certain plant foods with excessively high levels of oxalate, some of the oxalates don’t bind to the calcium in the body, and can travel to the kidneys. They will then leave the body by way of your urinary tract.

Your body uses food for energy. After your body uses what it needs, waste products travel through the bloodstream to the kidneys and are removed through urine. Urine has various wastes in it. If there is too much waste in too little liquid, crystals can begin to form. These crystals may stick together and form a solid mass (a kidney stone). Calcium oxalate stones are the most common type of kidney stone. Calcium oxalate stones can happen if there is too much oxalate, too little liquid, and the oxalate “sticks” to calcium while urine is being made by the kidneys.

There are different types of kidney stones. 8 out of 10 kidney stones are calcium oxalate stones. Your healthcare provider can test your stones to find what type you have.

Some Of The Plant-Based Foods That Are Relatively Rich In Oxalates:

Oxalate crystals

The mean daily intake of oxalate in English diets has been calculated to be 70-150 mg, with black tea appearing to contribute the greatest proportion of oxalate in these diets; spinach, rhubarb and beet are other common high oxalate-content foods.

Vegetarians who consume greater amounts of vegetables will have a higher intake of oxalates, which may reduce calcium availability. This may be an increased risk factor for women, who require greater amounts of calcium in the diet. Diets low in calcium and high in oxalates are not recommended but the occasional consumption of high oxalate foods as part of a nutritious diet does not pose any particular problem.

How Can You Lower Your Chances Of Forming Calcium Oxalate Stones?

  • Drink enough fluids. The number one thing you can do is to drink enough fluids, like water. Drinking enough fluids will thin out your urine and make it harder for chemicals to build up and form crystals. Your healthcare provider will look at your overall health, diet, and lifestyle and recommend the right amount of fluid you should have each day.

  • Avoid eating too much protein. Eating too many foods high in protein can cause stones to form.

  • Eat less salt (sodium). A diet high in salt (sodium) causes calcium to build in your urine. Too much calcium in your urine can lead to new stones. It can also cause your bones to weaken.

  • Include the right amount of calcium in your diet. Many people think they can keep stones from forming by avoiding calcium, but the opposite is true. Calcium is a nutrient that is found in dairy products, such as yogurt, milk and cheese. You need to eat calcium so that it can bind with oxalate in the stomach and intestines before it moves to the kidneys.

Eating foods with calcium is a good way for oxalates to leave the body and not form stones. The best way to get calcium into your body is through the foods you eat. It may seem easier to increase your calcium by taking a supplement. However, calcium in the form of a supplement may raise your chances of forming new calcium oxalate stones. Speaking with your healthcare provider will help you find the best way to include calcium in your diet. This will help avoid having too little or too much calcium in your body.

  • Broccoli — Broccoli is not only rich in calcium, but the absorption rate of calcium from broccoli is nearly 41%. That’s even higher than the absorption rate of calcium from traditional milk. Broccoli is a wonderful food when it comes to enriching your nutritional calcium intake.

  • Kale — Kale is also quite rich in calcium. And its calcium absorption rate is similar to that of broccoli at about 41%. Kale is another excellent choice if you are looking to up the calcium content in your diet.

  • Avoid vitamin C supplements. Talk to your healthcare provider before taking vitamin C supplements. Too much vitamin C can cause high amounts of oxalate in the urine.

  • Eat less oxalate-rich foods. Limiting how many oxalate-rich foods you eat each day may help lower your chance of forming new stones. There are some foods you should avoid because of their high oxalate levels. Some foods very high in oxalate are ...

    • Spinach

    • Rhubarb

    • Beets

    • Swiss chard

    • Chocolate soy milk

    • All Bran®

    • Buckwheat flour

    • Miso

    • Tahini

    • Sesame seeds

    • Nuts

  • Soaking and cooking of plant based foodstuffs high in oxalate will reduce the oxalate content by leaching.

Some more reading material on this topic:


bottom of page