Oxalates: What Are They, Risks, and Foods to Eat and Avoid

Key Takeaways

• Oxalates (or oxalic acid), natural anti-nutrients in plant foods, can reduce calcium absorption. 
• Healthy adults do not need to monitor oxalate intake.
• Individuals with certain health conditions may need to monitor their oxalate intake to prevent high levels and side effects. 

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As you delve into more complex nutrition topics, you may hear about ‘anti-nutrients’ or compounds in plant-based foods like fruits, vegetables, nuts, and beans.¹

Anti-nutrients are compounds found within foods that are generally very healthy and beneficial to the body. Anti-nutrients can restrict the availability of specific nutrients (like iron, zinc, or calcium) in food. This simply means that you would absorb less of some vitamins and minerals.¹

Anti-nutrients include oxalates, lectins, phytates, goitrogens, phytoestrogens, and tannins. Oxalates may inhibit calcium absorption and could increase some people's risk of kidney stone formation.¹

This article will explore oxalates, the difference between oxalic acid and oxalic acid, the possible health risks of oxalates and high-oxalate foods for specific individuals, and tips for maintaining a healthy oxalate level. 

What Are Oxalates and How Do They Differ From Oxalic Acid?

Oxalate, or oxalic acid, is a naturally occurring compound that can form insoluble salts with minerals like sodium, potassium, calcium, iron, and magnesium. Oxalates are found in plant foods. Oxalates are oxalic acid that joins to a mineral like calcium. In nutrition, oxalate and oxalic acid are used interchangeably as they act similarly upon the body.¹ 

Diet contributes to total oxalate levels within the body. However, the body makes its own oxalate at higher levels than what is typically eaten. 

Plant foods with the highest oxalates include spinach, swiss chard, amaranth, taro, sweet potatoes, beets, rhubarb, and sorrel. Raw legumes, whole grains, nuts, cocoa powder, and tea contain oxalates in small amounts. Not all oxalates found in foods are absorbable.¹ 

Are Oxalates Bad for You? 5 Health Risks

As you review the list of foods that contain oxalates, notice that most are beneficial foods for most people. You may wonder how oxalate-rich foods could have any health risks.

For most people, consuming oxalate-rich foods is of no concern and should be disregarded as it is not necessary to limit them.¹

Too much oxalate can exacerbate certain health conditions. Some individuals hyper-absorb oxalate or have altered gut health, increasing their oxalate absorption.^{1, 2} 

The body also produces more oxalate in response to high doses of some supplements (vitamin C), too much protein or protein supplement intake, and too little calcium intake.^{1, 3, 4}

Working with a healthcare provider and a registered dietitian can help you identify your risk and make specific dietary changes to manage your conditions. 

Oxalate-rich foods can impact the following health conditions:

• It May Contribute to Kidney Stones (But Not All Types of Kidney Stones!).

It’s essential to work with a dietitian and healthcare provider to determine the types of stones you produce and conduct 24-hour urine tests to determine if you have high oxalate levels and other factors such as dehydration or low calcium intake.^{1, 2} 

• Oxalates May Further Impair Existing Kidney Disease.

The kidneys primarily metabolize oxalates. People with altered kidney function can struggle to maintain appropriate levels of oxalates, leading to kidney damage, kidney stones, and heart complications.⁴ 

• It Can Cause Oxalosis (A Rare Genetic Metabolic Disorder).

Oxalasis is when the kidneys stop removing calcium oxalate crystals in the urine. The crystals build up in the eyes, bones, blood vessels, heart, and organs. If not treated with medications or dialysis, levels will continue to rise, causing damage and eventually death.⁴ 

• It Can Lead To Elevated Oxalate Levels in Individuals With Gastrointestinal Conditions or Conditions That Impact Digestion.

High oxalate levels can occur in people who have had Roux-en-Y gastric bypass, pancreatic insufficiency, short bowel syndrome, celiac disease, Crohn’s disease, cystic fibrosis, or use medications that treat these conditions.⁴ 

• It Can Prevent Nutrient Absorption in Diets Lacking Variety.

Research has found that diets containing primarily plant foods do not increase oxalate levels. 

Individuals following a DASH diet (high in plant foods containing oxalate) have a 40 to 50% decreased risk of kidney stones due to the beneficial nature of the plant foods (like calcium that binds oxalate and is excreted or antioxidants levels.)¹

However, people over-consuming oxalate-rich foods like almonds, almond milk, and spinach daily while under-consuming calcium-rich foods, too little variety from plant foods, and inadequate fluid intake could be at risk for calcium deficiency.²

For most healthy adults, oxalates are of no risk or concern. 

If you have kidney stones (specifically calcium oxalate kidney stones), kidney disease, genetic metabolic conditions impacting the kidneys, conditions impacting gastrointestinal absorption, or follow a limited diet, you may need to pay attention to your oxalate intake in light of your overall diet. 

Your body is unique; each individual absorbs and excretes oxalate at different levels. Working with a healthcare professional and dietitian can help you customize your diet and lifestyle to achieve a healthy balance of oxalates without eliminating all foods containing them.

What Foods Are High in Oxalates?

Plant foods contain the highest levels of oxalates. Food containing high levels include the following:

• Spinach
• Swiss chard
• Amaranth
• Almond products (almond milk and almond flour)
• Taro
• Kiwi
• Beets
• Rhubarb
• Star fruit
• Sorrel^{1, 2}

The following contain smaller amounts of oxalates:

• Raw legumes (soybeans are the highest, followed by lentils, peas, and chickpeas)
• Wheat bran cereal
• Sweet potatoes
• Potatoes
• Nuts (peanuts, cashews, and almonds)
• Cocoa powder
• Chocolate
• Tea^{1, 2}

While these foods contain oxalates in higher amounts than other plant foods, eliminating them is not recommended unless your healthcare provider has told you. 

You may need to balance high-oxalate foods with low-oxalate foods and ensure you consume adequate calcium at each meal (300-400mg) and water to balance oxalate levels. Be sure to watch your vitamin C supplementation as well.^{1, 2, 3}

Over 30 Foods for a Low Oxalate Diet

For individuals whose 24-hour urine test shows high levels of oxalates, reducing your intake of high oxalate foods and swapping for lower oxalate foods can help reduce your levels and any complications like kidney stones.⁵ 

You should drink enough fluid to make 2.5 liters of urine daily, consume 1,000 to 1,200 mg of dietary calcium, increase fruits and vegetables, and ensure no excessive animal protein intake.⁵

Here are some low oxalate foods to swap for the high oxalate foods:^{6, 7}

• Apples
• Avocado
• Bananas
• Tomatoes
• Parsley
• Cabbage
• Lettuce (Iceberg, Romaine)
• Kale
• Mustard greens
• Bok choy
• Okra
• Cauliflower
• Mushrooms
• Onions or scallions
• Peas
• Pickles
• Zucchini, yellow squash
• Blackberries
• Blueberries
• Cherries
• Limes
• Pears
• Pineapples
• Raisins
• Strawberries
• Apricots
• Cantaloupe, honeydew melon, watermelon
• Grapes
• Lemons
• Nectarines
• Papaya
• Peaches
• Plums
• Flaxseed

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6 Tips to Keep Your Oxalate Levels Low

Maintaining optimal oxalate levels is not solely dependent on foods containing oxalate. Multiple factors influence how the body handles oxalate. 

Here are some tips to keep oxalate levels in optimal ranges:

1. Balance High and Low Oxalate Foods for a Balanced Diet. Overconsuming specific high-oxalate foods daily could increase your oxalate levels, especially if you limit other plant foods simultaneously. 
2. Drink Plenty of Water. Research shows that consuming enough water to make 2.5 liters (or 83 ounces) of urine is ideal for optimal oxalate levels.⁵‍
3. Watch Your Vitamin C Supplementation. High levels can add to your daily oxalate formation.³‍
4. Ensure Your Calcium Intake Is at Least 1,000 to 1,200 MG Daily, With About 300 to 400 MG at Each Meal (Especially at Oxalate-Rich Meals). Calcium binds to oxalate, allowing your body to excrete it rather than absorb it.^{1, 2, 5} 
5. Cooking high oxalate vegetables and legumes to lower their oxalate content. 

For example, boiling spinach or Swiss chard for 12 minutes reduced oxalates by 85% to 87%. Steaming the spinach or Swiss chard reduced oxalate levels by 42% to 46%. Any wet cooking method reduces the oxalate levels.¹ 

Legumes and lentils should always be cooked to make them ideal for human consumption. Cooking lentils for 15 minutes reduced oxalate content by 43%. Canned legumes and beans had 86 to 93% lower oxalate levels than raw.¹ 

6. Work with your healthcare provider and registered dietitian to help you customize your diet and lifestyle to achieve a healthy balance of oxalates without eliminating all foods containing them.

The Bottom Line

Throughout this article, we explored oxalates, the difference between oxalic acid and oxalic acid, the possible health risks of oxalates and high-oxalate foods for specific individuals, and tips for maintaining a healthy oxalate level. 

Most healthy adults do not need to count or monitor their oxalate intake.

If you have kidney stones (specifically calcium-oxalate stones), kidney disease, genetic metabolic conditions impacting the kidneys, conditions impacting gastrointestinal absorption, or follow a limited diet, you may need to pay attention to your oxalate intake in light of your overall diet.

If you need to lower your oxalate intake, work with a registered dietitian to customize your calcium intake, low- and high-oxalate foods, fluid intake, and other health conditions to bring your oxalate levels within the optimal range.

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