Oxalates are natural compounds that plants produce. While generally harmless for most people, they can cause problems for certain individuals. You might be prone to kidney stones, for example. Around 9.9% of US adults experience kidney stones, and approximately 64% of these are calcium oxalate stones. This article helps you understand oxalate and guides you to avoid these high-oxalate foods. We will show you how to manage your oxalate intake.
Key Takeaways
Oxalates are natural compounds in plants. They can cause kidney stones for some people.
Many healthy foods contain high oxalate levels. These include spinach, almonds, and dark chocolate.
You can reduce oxalate intake. Boil vegetables, drink plenty of water, and eat calcium-rich foods with oxalate foods.
High oxalate levels can lead to kidney stones. They can also stop your body from absorbing important nutrients.
Choose low-oxalate foods. These include most meats, white rice, apples, and broccoli.
Understanding Oxalates
What Are Oxalates
Oxalates are natural compounds. Plants make them to protect themselves. You find them in many healthy foods. Oxalate is a compound with a specific chemical makeup, often written as C2O4^2-. It comes from oxalic acid. Your body also makes some oxalate on its own. This happens when your body breaks down certain substances. For most people, these compounds pass through the body without causing problems.
Why Oxalates Matter
Oxalates matter because they can cause issues for some people. When you eat foods with oxalate, it travels through your digestive system. Your body tries to get rid of it. It does this through your gut and kidneys. This process is called oxalate homeostasis. If your body has too much oxalate, or if it cannot get rid of it properly, problems can start.
For example, high oxalate levels can lead to kidney stones. This happens when oxalate combines with calcium in your kidneys. They form crystals. These crystals can grow into painful stones. High oxalate levels can also affect other parts of your body. Oxalate can deposit in tissues like your bones or thyroid. This can cause problems over time. Foods are considered high-oxalate foods if they contain more than 7 mg of oxalate per serving.
Your body balances oxalate from food and what it makes.
Too much oxalate can lead to kidney stones.
High oxalate levels can also deposit in other body tissues.
Your gut and kidneys work to manage oxalate.
High-Oxalate Foods to Avoid
You need to know which foods contain high levels of oxalate if you are managing your intake. Many healthy foods naturally contain oxalate. However, some have much more than others. Knowing these specific items helps you make informed choices. Here, you will learn about common high-oxalate foods across different categories. This helps you understand what to limit or avoid.
High-Oxalate Greens
Leafy greens are often very healthy. Yet, some greens are foods high in oxalate. You should be mindful of these if you need to reduce your oxalate intake.
Spinach: This popular green is very high in oxalate.
Beet Greens: These are the leafy tops of beets. They also contain a lot of oxalate.
Swiss Chard: This leafy green is another common source of oxalate.
Look at the table below to see just how much oxalate some of these greens contain:
Green | Oxalate Content (per 1 cup, raw) |
|---|---|
Spinach | 656mg |
Chard | 350mg |
High-Oxalate Fruits
Fruits are good for you. Still, some fruits carry a higher oxalate load. You might want to eat these in smaller amounts.
Raspberries: These berries are delicious but contain significant oxalate.
Dates: These sweet fruits are also high in oxalate.
Here are some specific oxalate amounts for certain fruits:
Raspberries: 48mg oxalate per cup
Dates: 24mg oxalate per date
Canned Pineapple: 24mg oxalate per 1/2 cup
Dried Pineapple: 30mg oxalate per 1/2 cup
High-Oxalate Nuts and Legumes
Nuts and legumes offer protein and fiber. However, many of them are high in oxalate. You should consider this when planning your meals.
Almonds: These popular nuts have a high oxalate content.
Navy Beans: These beans are a common source of oxalate.
Fava Beans: You will find a notable amount of oxalate in fava beans.
Okra: This vegetable, often used like a legume, also contains oxalate.
Many nuts contain high levels of oxalate. Published values exist for almonds, cashews, hazelnuts, peanuts, pecans, pistachios, and walnuts. You can see the oxalate content in various legumes in the table below:
Legume Type | Total Oxalate (mg/100g) | Soluble Oxalate (mg/100g) |
|---|---|---|
Raw Soybean | 370.5 | 200.7 |
Peas | 244.7–294.0 | Approximately 24–72% of total |
Lentils | 168.6–289.1 | Approximately 24–72% of total |
Fava Beans | 241.5–291.4 | Approximately 24–72% of total |
Chickpeas | 92.2–214.0 | Approximately 24–72% of total |
Common Beans | 98.86–117.0 | Approximately 24–72% of total |
This chart also shows the total oxalate content in different legumes:
High-Oxalate Grains
Some grains and grain products can contribute to your oxalate intake. You might want to choose alternatives if you are trying to avoid these high-oxalate foods.
Brown Rice Flour: This flour contains more oxalate than white rice flour.
Bulgur: This cracked wheat product is another source.
Buckwheat: You will find oxalate in buckwheat and its products.
Cornmeal: This common ingredient also has oxalate.
Soy Flour: Made from soybeans, soy flour is high in oxalate.
Wheatberries: These whole wheat kernels contain oxalate.
High-Oxalate Drinks
What you drink can also add to your oxalate levels. Some popular beverages are surprisingly high in oxalate.
Dark Beer: This type of beer can contain significant oxalate.
Black Tea: Many people drink black tea daily. It is a major source of oxalate.
Chocolate Milk: The cocoa in chocolate milk makes it high in oxalate.
Cocoa: Pure cocoa powder is very high in oxalate.
Instant Coffee: Some instant coffees can contribute to your oxalate intake.
Here is a look at the oxalate content in some beverages:
Beverage Type | Oxalate Content (mg kg⁻¹) |
|---|---|
Rhubarb Nectar (60% juice) | 198.3 (total), 197.1 (soluble) |
Beetroot Juices | Highest among fruit/vegetable juices, nectars, and drinks |
You can also see the high oxalate levels in different types of tea:
Beverage Type | Oxalate Content (mg kg⁻¹) |
|---|---|
Black Tea | 1500 – 6900 |
Green Tea | 680 |
Oolong Tea | 230 |
Herbal Teas (general) | 3.21 – 6.34 (mL) |
Other High-Oxalate Items
Beyond the categories above, several other common foods are high in oxalate. You should be aware of these as well.
Potatoes: Especially baked potatoes, they contain oxalate.
Beets: These root vegetables are known for their high oxalate content.
Chocolate: Dark chocolate and cocoa products are significant sources.
Soy Products: Tofu, soy milk, and other soy-based items are high in oxalate.
Olives: These small fruits also contain oxalate.
This table shows the oxalate content for various high-oxalate foods:
Food Item | Serving Size | Oxalate Content (mg) |
|---|---|---|
Spinach | 0.5 cup (cooked) | 755 |
Firm Tofu | 3 ounces | 235 |
Soy Milk/Yogurt | 1 cup | Up to 336 |
Almonds | 1 ounce (approx. 22 nuts) | 122 |
Baked Potato | 1 medium | 97 |
Beets | 1 cup | 152 |
Navy Beans | 0.5 cup | 76 |
Raspberries | 1 cup | 48 |
Dates | 1 date | 24 |
You can also visualize these amounts in the chart below:
Knowing these high-oxalate foods helps you manage your diet. You can make informed choices to avoid these high-oxalate foods if you are at risk for kidney stones or other oxalate-related issues.
Health Risks of Oxalate
Understanding the potential health risks of oxalate is important. While oxalates are natural, they can cause problems for some people. You should know these risks to manage your diet effectively.
Kidney Stone Formation
The most well-known risk of oxalate is kidney stone formation. When you have high oxalate levels, oxalate can combine with calcium in your kidneys. This forms crystals. These crystals initially form within your renal tubules.
Most crystals pass out in your urine. However, some crystals attach to the surface of renal tubular cells. In healthy people, your body usually breaks down these attached crystals. If you have hyperoxaluria or crystal urine, your renal tubular cells can get damaged. This increases their susceptibility to crystal attachment. These attached crystals are then absorbed into the cells. Inside the cells, these crystals grow. They eventually form a kidney stone.
Even though your urine almost always has a lot of calcium oxalate, only a few people get kidney stones. This means other factors play a role. These factors include crystal structure and your body’s own molecules.
If you develop kidney stones, you might experience sharp pains in your back, side, lower belly, or groin. You might also feel nausea and vomit. Blood in your urine is another symptom. You could also have pain during urination or a frequent urge to urinate. Knowing these signs helps you act quickly to prevent kidney stones.
Nutrient Absorption Interference
Oxalates can also interfere with your body’s ability to absorb important nutrients. Oxalates bind to essential minerals in your digestive tract. These minerals include calcium and magnesium. This binding makes the minerals unavailable for your body to absorb. This reduces their usefulness. Oxalates specifically bind with calcium. They form insoluble salts. Your body finds these salts hard to absorb. This leads to less calcium being available. This is especially important for bone health. It can worsen bone density loss. Beyond calcium, oxalates can also affect the absorption and usage of other nutrients. These include glutathione, biotin, and sulfate.
Other Potential Concerns
Beyond kidney stones and nutrient issues, high oxalate levels can lead to other health problems. Oxalate crystals can form in different parts of your body. These include your bones, joints, blood vessels, lungs, thyroid, and brain.
This can harm how these organs work. Their sharp structure can cause pain and damage. They may also increase inflammation. In your bones, oxalate crystals can replace bone marrow cells. This can lead to anemia and a weaker immune system. Iron oxalate crystals can cause damage and reduce iron stores.
This affects red blood cell production. Oxalates can also bind to toxic metals like mercury and lead. However, they can trap these metals in your tissues. This contributes to metal toxicity. Oxalates can also interfere with glucose metabolism. They can inhibit the absorption of essential minerals.
High oxalate intake can also irritate your gut. This is especially true if you have conditions like leaky gut or IBS. It can trigger inflammation and an imbalance of gut bacteria. Oxalate crystals can build up in tissues. This causes joint pain, stiffness, and inflammation. This is relevant for people with fibromyalgia or chronic fatigue syndrome.
Managing Oxalate Intake
You can manage your oxalate intake. This helps you reduce the risk of health problems. You can use practical strategies. These strategies help you lower the amount of oxalate you consume. They also help your body deal with oxalate more effectively.
Cooking Methods to Reduce Oxalates
Cooking can significantly reduce the oxalate content in many foods. You can use different methods. Boiling is very effective. It helps leach soluble oxalate from vegetables. Air frying and microwaving also work.
Cooking Method | Vegetable | Initial Oxalate (mg/g) | Reduced Oxalate (mg/g) | Reduction (%) |
|---|---|---|---|---|
Boiling (2-8 min) | Kale | 0.88 | 0.22 | 75% |
Spinach | 3.10 | 1.44 | 53.5% | |
Beans | 4.10 | 2.42 | 41% | |
Carrot | 4.10 | 2.42 | 41% | |
Tomatoes | 5.50 | 4.40 | 20% | |
Air Frying (15 min) | Kale | N/A | 0.20 | N/A |
Spinach | N/A | 1.32 | N/A | |
Beans | N/A | 0.44 | N/A | |
Carrot | N/A | 0.46 | N/A | |
Tomatoes | N/A | 1.54 | N/A | |
Microwave (1-5 min) | Kale | 0.77 | 0.44 | 42.9% |
Spinach | 2.42 | 0.88 | 63.6% | |
Beans | 4.62 | 2.86 | 38.1% | |
Carrot | 0.98 | 0.32 | 67.3% | |
Tomatoes | 6.38 | 4.35 | 31.8% |
Boiling and air frying show higher reductions than microwaving. This happens because soluble oxalate leaches out. The cooking process disrupts plant tissues. This allows the oxalate to escape. Boiling can reduce total oxalate by 17-48% in most samples. It reduces soluble oxalate by 31-48%.
Dietary Adjustments
You can make specific changes to your diet. These changes help manage high oxalate levels. Consider creating an oxalate diet plan.
Meal Planning: Plan your meals weekly. This ensures a balanced diet. It also keeps oxalate levels low.
Food Combinations: Combine calcium-rich foods with oxalate-containing foods. This binds oxalate in your intestine. It prevents absorption. Magnesium-rich foods also help bind oxalate.
Preparation Techniques: Soak pulses and cereals overnight. Drain the water. Cook leafy greens like spinach. Pour away the cooking water. These steps reduce oxalate content.
Fermentation: Eat fermented foods. Sauerkraut is an example. Natural microorganisms break down oxalate during fermentation. This can reduce oxalate levels significantly.
Nutritional Supplements: Talk to your doctor about probiotics. They can metabolize oxalate. Enzymes like oxalase also convert oxalate.
Hydration and Excretion
Drinking enough water is crucial. It helps your body excrete oxalate. This helps prevent kidney stones. You should drink at least two liters of water daily. This flushes oxalate from your kidneys. Increase your intake in hot weather. Drink more during physical activity. Water, herbal teas, and diluted fruit juices are good choices. Avoid sugary drinks and alcohol.
Association | Recommended Daily Fluid Intake | Recommended Daily Urine Output |
|---|---|---|
European Association of Urology | 2.5–3.0 L/day | 2.0–2.5 L/day |
Canadian Urological Association | Not specified | 2.5 L/day |
American College of Physicians | Not specified | At least 2.0 L/day |
American Urological Association | Not specified | At least 2.5 L/day |
If you have a high risk for kidney stones, you might need more fluid. Some recommendations suggest 3.5–4 L/day.
Calcium’s Role in Oxalate Binding
Calcium plays a key role in managing oxalate. Oxalate binds with calcium in your intestines. This forms calcium-oxalate crystals. This happens when oxalate and calcium come from the same food. This can reduce calcium absorption. However, if oxalate and calcium come from different foods, oxalate does not decrease calcium absorption. For example, eat almonds with milk.
The calcium from the milk will not be hindered. Eating oxalate-containing foods with calcium-rich foods can protect against kidney stone formation. Ensure you consume the recommended amount of calcium. This is important for a low-oxalate diet.
Low-Oxalate Food Choices
You can still enjoy a wide variety of delicious and nutritious foods even if you follow a low-oxalate diet. This section helps you identify excellent alternatives to high-oxalate foods. You can make informed choices to manage your oxalate intake effectively.
Low-Oxalate Proteins
You have many protein options that are naturally low in oxalate. These foods provide essential nutrients without adding to your oxalate load.
Meat: All types of meat, including beef, pork, and lamb, are good choices.
Fish and Shellfish: You can enjoy most fish and shellfish.
Poultry: Chicken, turkey, and duck are excellent protein sources.
Eggs: Eggs are a versatile and low-oxalate protein.
Dairy Products: Milk, cheese, and yogurt are generally low in oxalate. They also provide calcium, which helps bind oxalate in your gut.
Low-Oxalate Grains and Starches
You can choose specific grains and starches that are low in oxalate. These options help you maintain a balanced diet.
White Rice: This is a good alternative to brown rice.
White Bread: You can include white bread in your low-oxalate diet.
Pasta: Most types of pasta are also low in oxalate.
Low-Oxalate Fruits and Vegetables
Many fruits and vegetables are foods low in oxalate. You can include these in your meals to ensure you get enough vitamins and minerals.
Here are some commonly accepted low-oxalate fruits:
Apples
Bananas
Cherries
Grapes
Melons (cantaloupe, honeydew, watermelon)
Peaches
Pears
You also have a wide selection of low-oxalate vegetables. These vegetables are great for your health.
Vegetable | Average total oxalate per 100 g (mg) |
|---|---|
Artichoke, boiled | 13 |
Arugula, raw | 7 |
Asparagus, boiled or steamed | 6 |
Beans, Green, Variety, boiled or steamed | 24 |
Beans, Lima or Butter, boiled 30 min | 10 |
Beans, Mung | 3 |
Bok Choy, leaves | 8 |
Bok Choy, stalks, diced | 2 |
Broccoli, boiled or steamed | 7 |
Broccoli, raw | 12 |
Turnip, boiled, steamed or raw | 3 |
Water Chestnuts, canned, sliced, Dynasty | 2 |
Watercress, raw | 8 |
You can see how low the oxalate content is in many common vegetables:
Other excellent low-oxalate vegetable choices include:
Mustard greens
Cabbage
Cauliflower
Mushrooms
Onions
Peas
Zucchini
Choosing these foods helps you maintain a healthy and balanced low-oxalate diet.
You now understand that many healthy foods contain oxalate. However, you must be mindful of your oxalate intake if you are at risk for kidney stones. You should limit high-oxalate foods like spinach and nuts. Always combine high-oxalate foods with calcium-rich options. This helps prevent stone formation. Remember to consult a healthcare professional or registered dietitian for personalized advice. For most people, these foods are beneficial. Yet, awareness is key to avoid these high-oxalate foods if you are at risk.