Oxalates in Food: Dangerous or Healthy?

Vegetables, while healthy, can also contain antinutrients like oxalates. Unfortunately, these are less healthy. They inhibit mineral absorption and can negatively impact your health.

However, that doesn't mean you should avoid all vegetables containing oxalates. Many foods contain both beneficial and less beneficial ingredients. Grains, for example, also contain antinutrients.

You can partially mitigate the downsides by cooking, for example, but you can also pay attention to variety in your diet. This article explains everything about oxalates, their sources, and their health consequences.

Oxalates are organic acids found in plants. They are antinutrients produced by plants and serve to protect them. Some plants contain more oxalate (also called oxalic acid) than others.

The substances are found in vegetables (spinach, beets, Brussels sprouts), fruit, nuts, seeds and cocoa [1] . When you ingest oxalates through food, these substances form compounds with minerals. For example, magnesium or calcium oxalate is formed.

This usually occurs in the large intestine, but can also occur in the kidneys or urinary tract. Your body generally excretes these substances through feces. However, in some people, oxalates can cause health problems.

Oxalates have the disadvantage of binding to minerals in the intestines. This prevents the body from absorbing these minerals. Spinach, for example, contains a lot of calcium, but also oxalic acid. Because these substances form a compound (calcium oxalate), you can hardly absorb the calcium [2] .

Eating fiber along with foods high in oxalate can also cause problems, further limiting nutrient absorption [3] .

It's important to remember that not all minerals in our diet bind to oxalic acid. When you eat spinach with a glass of milk, the absorption of calcium from the milk is not affected by the oxalic acid in the spinach.

Kidney stones can be formed from calcium and oxalate. These substances are always present in the urinary tract. But as long as they remain dissolved, they won't cause any problems.

However, if they form crystals and subsequently kidney stones, problems do arise. This can happen when oxalate levels are high and urine output is low. Large kidney stones are very painful. As the stones move through the urinary tract, blood can appear in the urine.

Kidney stones can be formed from a variety of components, but 80% are made up of calcium oxalate [4] . If you have had kidney stones several times, it may be advisable to pay attention to a diet that is high in oxalates.

However, this isn't always necessary. The body can also produce oxalic acid on its own. Your doctor can test how much of the substance your body excretes in your urine. If you have high levels of oxalic acid in your urine, your doctor may recommend adjusting your diet.

Oxalates are not beneficial for the body. They are meant to be excreted quickly. If they pass through the intestines and leave your body in the stool, there's no problem.

However, this can be the case for people with intestinal problems, such as IBS and Leaky Gut Syndrome. Because the intestinal wall is damaged, there's a chance your body will absorb more oxalic acid. In that case, oxalates can worsen the symptoms of these conditions.

In addition, oxalic acids can in principle affect almost every system in the body: the nervous system, the immune system and the skeleton [5] [6] .

It can therefore cause the following complaints:

• Sleep problems
• Difficulty learning and concentrating
• Autism
• Autoimmune diseases
• Joint pain
• Could be an underlying cause of fibromyalgia.

Now that you know that certain vegetables contain oxalates, you might think it would be better to avoid them. However, that would be a shame, because oxalate-rich foods contain valuable nutrients.

You'll also miss out on many of the benefits this vegetable offers, such as fiber, antioxidants, and vitamins. These help support your immune system and promote healthy bowel function.

It's wiser to be mindful of what you eat. Oxalic acid does have a negative impact on the body, but that doesn't necessarily have to be a problem within a varied diet. If you're mindful of your intake, you can enjoy and benefit from vegetables that contain oxalates.

For example, many people enjoy eating smoothies every day instead of bread. But if you add raw spinach and nuts to your smoothies every time, you could be consuming significantly higher amounts of oxalic acid.

Then your body might be less able to absorb all the nutrients. If that's the case, vary the vegetables you eat. Use other sources of protein instead of nuts.

If you only eat vegetables rich in oxalic acid occasionally, you are unlikely to get too much or to suffer from deficiencies.

Healthy gut flora is important for processing these substances. The bacteria in your intestines can break down some oxalates. This happens before they can bind to minerals, preventing deficiencies from developing.

There are even bacteria, such as Oxalobacter formigenes, that use oxalates as a source of energy. This bacteria partly prevents your body from absorbing the acids [7] .

However, there are several reasons why people do not have sufficient numbers of this bacteria in their intestines and for whom oxalates can more quickly become a problem. Antibiotics, for example, can cause a decrease in Oxalobacter colonies [8] .

If you suffer from inflammatory bowel disease, you are also at a higher risk of developing kidney stones [9] . This is partly because in that case the body cannot properly regulate the absorption of oxalic acid.

Digestive surgery also negatively impacts the processing of oxalic acid. Elevated oxalate levels have been found in the urine of patients who underwent gastric bypass.

This same effect can be seen in all operations that involve interventions that alter the functioning of the digestive system.

In these cases, a diet that limits oxalate intake may be beneficial.

In the overview below you will find products that contain a lot of oxalic acid.

Mg oxalic acid per 100 grams:

• Rhubarb (520 mg)
• Spinach (970 mg)
• Beets (275 mg)
• Swiss chard (610 mg)
• Endive (110 mg)
• Brussels sprouts (360 mg)
• Cocoa powder (700 mg)
• Kale (20 mg)
• Sweet potatoes (240 mg)
• Peanuts (150 mg)
• Lettuce (330 mg)
• Turnip greens (210 mg)
• Carrot (500 mg)
• Radish (480 mg)
• Broccoli (190 mg)

You can reduce the amount of oxalates in your diet by preparing food correctly. There are two good ways:

If you choose vegetables rich in oxalate, cook them first. Cooking can reduce the amount of oxalic acid in your food by 30 to 90% (depending on the type of vegetable).

The oxalates aren't broken down; they're simply dissolved and released into the water. Because you drain the vegetables afterward (which you should do in this case), your meal will be less rich in oxalates.

Steaming is less effective than boiling, but it does help reduce oxalate levels. It works particularly well with carrots and spinach.

Other cooking methods, such as stir-frying, do not reduce these substances. The moisture released during stir-frying remains in the dish, and therefore the oxalates as well.

It's clear that oxalates can have a detrimental effect on health. They can cause kidney stones, worsen intestinal problems, and could be the underlying cause of mineral deficiencies.

But it would be a shame and unnecessary to completely eliminate these vegetables from your diet. With normal consumption, oxalates probably don't cause any problems. However, it's wise to ensure you eat a varied diet.

If you love smoothies, don't always choose spinach. If you're vegetarian, pay close attention to which vegetables you eat and keep varying your intake. This way, you'll eat healthily and keep oxalate levels under control.