What are oxalates and what do we need to know about them?
Oxalates, (also referred to as oxalic acids*), are naturally occurring compounds found in several plant-based foods. They are sometimes called “anti-nutrients”- substances that impede the absorption of certain nutrients from food. Oxalates specifically impact the absorption of minerals like calcium, magnesium, and iron. This reduces the bioavailability of these minerals in the foods we eat and can have implications for our bone health.
Are oxalates harmful?
We all know that calcium, (along with many other nutrients), is vital for maintaining strong, healthy bones. When calcium-rich foods are consumed alongside foods rich in oxalates, the calcium binds to the oxalates in the digestive tract. This process can decrease (but not completely eliminate) the bioavailability of calcium, potentially leading to calcium deficiency over time.
Oxalates are generally harmless in moderate amounts and are typically excreted in the urine. But if oxalate-rich foods dominate the diet without adequate mineral intake or proper preparation techniques, as we’ll discuss, there is a possible risk of mineral deficiencies impacting bone health.
What foods are high in oxalates?
Some common foods with the highest levels of oxalate content are listed below in alphabetical order**.
- almonds
- avocados
- beets and beet greens
- cashews
- chard
- cocoa products
- dark chocolate
- dates
- grains such as wheat flour or whole grain products
- grapefruit
- legumes such as navy, red kidney, and fava beans
- okra
- parsley
- peanuts
- raspberries
- rhubarb
- sesame seeds
- spinach
- tofu
- yams
This list, which is just a sampling of oxalate-rich foods, may be disturbingly longer than you expected. But do we need to completely eliminate these foods from our diet? The answer is a resounding “No!”
Dietary strategies: reducing the impact of oxalates
Each of these foods can contribute to a balanced, healthy diet, so instead of avoiding them, a much better strategy is to understand how to mitigate their impact on our bone health and increase the bioavailability of the minerals they contain.
- Food preparation:
- Boiling high-oxalate vegetables can significantly reduce their oxalate content because oxalates are water-soluble and leach into the cooking water.
- Steaming or baking also reduces oxalate content but to a lesser extent than boiling.
- Discard the cooking water to maximize oxalate reduction.
- Separate calcium-rich and high-oxalate foods:
- Try to eat calcium-rich foods like cheese, yogurt, or fortified plant milks at different times than high-oxalate foods to reduce oxalate binding.
- Drink plenty of water: Staying well-hydrated not only dilutes oxalates, but it also promotes healthy kidney function.
- Moderate your consumption of high-oxalate foods: This includes lower portion sizes as well as eating them less frequently.
- Substitute low-oxalate greens. Some examples include:
Be aware that some people are at greater risk
Individuals with certain medical conditions, listed below, may be more susceptible to the adverse effects of high-oxalate diets.
- People prone to kidney stones (particularly calcium oxalate stones): High oxalate intake can increase the risk of forming calcium oxalate kidney stones, the most common type. The salts produced by oxalates can crystallize in the urine and act as a trigger for kidney stones. Managing oxalate consumption may be recommended as a possible prevention strategy.
- Malabsorption disorders (such as Crohn’s or Celiac disease): These conditions may exacerbate oxalate-related mineral absorption problems.
- Existing kidney disease: Reduced kidney function hampers oxalate excretion, so limiting oxalate-rich foods can help prevent accumulation and complications.
- Hyperoxaluria: A rare condition characterized by excessive oxalate in the urine. It can be hereditary or secondary to other health issues and reducing dietary oxalates can help prevent kidney damage.
If you have any of these conditions, consult your healthcare provider for personalized dietary guidance.
The takeaway
While many foods containing oxalates are part of a healthy diet for most people, excessive consumption without consideration can potentially impact mineral absorption and bone health. Balancing oxalate-rich foods with calcium intake and maintaining overall nutritional health are key strategies in supporting strong bones.
*While they are the same substance, oxalate technically refers to the acid after it has bound to minerals like calcium, while oxalic acid is the free, organic acid form.
** For a comprehensive list of the oxalic acid content in food, go to:
https://ucikidneystonecenter.com/wp-content/uploads/2020/06/Oxalate-Content-of-Foods.pdf (University of California at Irvine)
For further reading:
Gaur A, et al. Food Oxalates: Occurrence in the Food System and Advances in Technologies for Reduction, Detection, and Quantification. Comprehensive Reviews in Food Science and Food Safety. 2025;24(4):e70212.
