Oxalate (Oxalic Acid): Are These Foods Bad for You?

It’s no secret that foods like spinach, broccoli and sweet potatoes have health benefits. But did you know that they also have a lot of oxalates?

Oxalates are organic compounds that can accumulate in the kidneys, increasing the risk of painful kidney stones. But while a low-oxalate diet was once a treatment for kidney stones, emerging research now shows that you may not need to eliminate oxalates from your diet altogether.

So what are oxalates, how can they affect your health, and do you really need to reduce your intake? Here’s what you need to know.

What are Oxalates?

Oxalates, also known as oxalic acid, are natural compounds found in a range of food sources. Some of the most common oxalates in food are found in plant sources such as fruit, vegetables, nuts and seeds. Oxalate can also be produced naturally by your own body.

Oxalates often bind to minerals such as calcium and are excreted from the body through the stool. However, high amounts of oxalate can build up in the kidneys, leading to the formation of kidney stones.

Kidney stones occur when hard mineral deposits form within the inner lining of the kidneys, causing symptoms such as stomach pain, nausea and vomiting. Although there are several different types of kidney stones, calcium oxalate stones are considered to be one of the most common.

A traditional kidney stone diet involves limiting the consumption of oxalate foods to prevent the formation of these painful mineral deposits. However, many oxalate foods are rich in other nutrients and often double as fiber-rich foods, also high in magnesium.

Rather than cutting these foods out of your diet entirely, recent research has found that increasing your calcium intake may be just as effective in preventing kidney stones.

Are Oxalates Bad For You?

Oxalates are considered anti-nutrients, meaning they can bind to certain minerals in the body and prevent their absorption. Calcium, in particular, binds to oxalate and is excreted from the body, which can be a problem for those who eat a high-oxalate, low-calcium diet.

However, most research generally suggests that there are unlikely to be any adverse health effects from moderately high oxalate foods as part of a healthy diet. Additionally, soaking or cooking foods can significantly reduce oxalate levels to maximize nutrient absorption.

Kidney stones are another common concern related to oxalate consumption. This is because high amounts of oxalates can accumulate in the kidneys, contributing to the formation of kidney stones.

Although reducing your intake of high-oxalate foods may help reduce the risk of kidney stones, many of these foods are rich in other important vitamins and minerals that your body needs.

In addition, studies show that combining oxalate foods with calcium-rich foods may promote oxalate excretion from the body, without removing any oxalate-rich foods from your refrigerator.

High Oxalate Foods

Oxalates are found in most plant foods in varying amounts, including many fruits, veggies, nuts and seeds. Meanwhile, most animal products such as meat, fish and poultry contain only trace amounts of oxalates.

Here are some of the best foods high in oxalates:

• Results: Blackberries, blueberries, raspberries, kiwis, tangerines, figs
• Vegetables: broccoli, rhubarb, okra, leeks, beets, potatoes, eggplant, sweet potatoes, zucchini, carrots, celery, olives, rutabaga, parsley, chicory, peppers
• Leafy greens: spinach, escarole, beet green, kale, collards, swiss chard
• Nuts and Seeds: almonds, cashews, peanuts, sesame seeds
• Legumes and Soy Products: miso, tofu, soya milk, green beans and kidney beans
• Grains: bulgur, corn grits, wheat germ, whole wheat bread, amaranth, buckwheat and quinoa
• Drinks: cocoa/chocolate, chocolate milk, black tea, instant coffee, dark beer

Some foods also contain moderate amounts of oxalates and can be incorporated into a low-oxalate diet. Here are some oxalate-moderate foods:

• Results: apples, oranges, prunes, pears, pineapple, peaches, apricots
• Vegetables: artichokes, fennel, canned peas, asparagus, tomatoes, lima beans, Brussels sprouts, mustard greens, turnips, onions, parsnips, corn
• Drinks: brewed coffee, carrot juice, tomato juice, orange juice

low-oxalate diet

If you are trying to find out how to prevent kidney stones, a low-oxalate diet is often recommended, especially if you are at risk of kidney stones.

A low-oxalate diet usually provides less than 40-50 milligrams of oxalates per day. In addition to limiting your intake of oxalates, staying well hydrated, moderating your protein intake and increasing calcium consumption are other important aspects of a low-oxalate diet. It is usually recommended to follow the diet for at least 3-6 weeks to see if your symptoms improve.

Here are some simple steps on how to follow a low oxalate diet:

1. Moderate Consumption of High Oxalate Foods

Reducing your intake of high-oxalate foods from the list above may help prevent kidney stones.

However, there is no need to cut these foods from your diet entirely. In fact, recent research suggests that increasing your calcium intake may boost oxalate excretion and may be more effective against kidney stones.

2. Enjoy a Variety of Low-Oxalate Foods

There are plenty of nutrient dense foods that are low in oxalates and can be enjoyed as part of a healthy balanced diet. Some of the best foods you can include in a low-oxalate diet include:

• Results: bananas, cherries, mangoes, grapefruit, melons, grapes, nectarines, papaya
• Vegetables: cauliflower, kohlrabi, radishes, chives, mushrooms, cucumbers, cabbage, peas, avocados
• Proteins: meat, poultry, seafood and eggs
• Dairy products: milk, cheese, yogurt, butter
• Grains: rice, corn bran, rye bread, egg noodles
• Drinks: water, herbal tea, wine
• Herbs and Spices: Rosemary, oregano, basil, turmeric, ginger, dill

3. Increase Your Intake of Calcium-Rich Foods

Oxalate and calcium bind together, which may help prevent kidney stones. Therefore, it is recommended to pair oxalate foods with foods high in calcium, including sardines, yogurt, kefir, cheese and almonds.

Ideally, aim for 2-3 servings of calcium-rich foods a day.

4. Drink Plenty of Water

Water can help flush materials out of the kidneys to help protect against kidney stones. To stay well hydrated, try to drink at least 8 8-ounce glasses of water or fluids a day.

5. Moderate Protein Intake

Eating too much animal protein can contribute to the formation of kidney stones. In a healthy diet, between 10-35 percent of total daily calories should come from protein, which can come from sources such as meat, fish and poultry as well as legumes, nuts and seeds.

6. Cook/Soak Oxalate Foods

Boiling and steaming can help reduce oxalate levels in certain foods, including greens and other veggies. Try boiling vegetables for 6-10 minutes or steaming them for several minutes until soft.

Soft grains and legumes can also help reduce oxalate content while minimizing levels of other anti-nutrients such as phytase, protease inhibitors, lectins and tannins. For help with soaking and sprouting foods, check out this handy sprout guide.

7. Try a Supplement

Some people choose calcium citrate, NAG (N-Acetyl-Glucosamine), CMO (cetyl myristoleate) or a combination of these supplements to deal with side effects or pain associated with oxalic acid.

To help manage your symptoms, you can ask your healthcare provider if these might be helpful for you.

Final Thoughts

• Oxalates are natural compounds found in a variety of plant foods, including many fruits, vegetables, nuts and seeds.
• In high amounts, oxalates can accumulate in the kidneys, leading to the formation of kidney stones.
• Although following a low-oxalate diet was once recommended to prevent kidney stones, recent research suggests that eating more calcium-rich foods may be more effective in increasing oxalate excretion.
• Enjoying a variety of low-oxalate foods, drinking plenty of water, cooking or soaking oxalate foods and limiting your intake of animal proteins may also be beneficial.