These days, leafy green vegetables and other plant based food items are extremely popular among the health-conscious section of the population. While it’s true that these vegetables are extremely rich in nutrients that are great for health, many of them also contain an antinutrient called oxalic acid (oxalate). In this post, we will discuss everything you need to know about oxalic acid (oxalate).
What is oxalic acid (oxalate)?
Oxalic acid is an organic compound that is found in many plants that we consume.
These include leafy greens, vegetables, fruits, cocoa, nuts and seeds.
In plants, oxalic acid usually bonds itself to minerals and forms oxalic acid (oxalate). However, the terms “oxalic acid” and “oxalic acid (oxalate)” are interchangeable as far as nutrition science is concerned.
The human body produces oxalic acid (oxalate) on its own or acquires it from food. Vitamin C can also be converted into oxalic acid (oxalate) when it’s metabolized
Once it’s consumed, oxalic acid (oxalate) binds itself to minerals to form different compounds such as calcium oxalic acid (oxalate) and iron oxalic acid (oxalate). This process usually happens in the colon. However, it can also occur in parts of the urinary tract or the kidneys.
For most people, these compounds are then eliminated in the stool or urine.
However, for sensitive individuals, high-oxalic acid (oxalate) diets have been linked to an increased risk of kidney stones and other health problems.
In short, Oxalic acid (oxalate) is an organic acid which is found in plants, but the human body can synthesize it as well. It binds minerals, and has been linked to kidney stones and other health problems in some cases.
Oxalic acid (oxalate) Can Reduce Mineral Absorption
One of the chief health concerns associated with oxalic acid (oxalate) is that it can bind itself to the minerals present in the gut and prevent their absorption by the body.
Case in point is Spinach. Its calcium and oxalic acid (oxalate) content is very high, which in turn prevents a lot of the calcium from being absorbed into the body.
Eating fiber and oxalic acid (oxalate) together may further hinder nutrient absorption.
Nevertheless, it’s important to remember that only some of the minerals in our food will bind to oxalic acid (oxalate).
Even though oxalic acid (oxalate) reduces calcium absorption from spinach, it doesn’t reduce calcium absorption if you consume milk and spinach together.
Oxalic acid (oxalate) May Contribute to Kidney Stones
Normally, calcium and small amounts of oxalic acid (oxalate) are present in the urinary tract at the same time, but they remain dissolved and cause no problems.
However, sometimes they bind to form crystals. In some people, these crystals can lead to the formation of stones, especially when oxalic acid (oxalate) is high and urine volume is low (5Trusted Source).
Small stones often don’t cause any problems, but large stones can cause severe pain, nausea and blood in the urine as they move through the urinary tract.
Though other types of kidney stones exist, over 80%, or four out of five kidney stones are made of calcium oxalic acid (oxalate).
For this reason, people who have had one episode of kidney stones may be advised to minimize their consumption of foods high in oxalic acid (oxalate).
However, all patients suffering (or have suffered) from kidney stones don’t need a blanket restriction on oxalic acid (oxalate) in their diet. This is because most of the oxalic acid (oxalate) found in urine is produced by the body, rather than absorbed from food
Most urologists now only prescribe a strict low-oxalic acid (oxalate) diet (less than 50 milligrams per day) for patients who have high levels of oxalic acid (oxalate) in their urine (6Trusted Source).
Therefore, it’s important to be tested from time to time to figure out how much restriction is necessary.
In short, high-oxalic acid (oxalate) foods may increase the risk of kidney stones in susceptible people, and recommendations for patients are based on urinary levels.
Does it Cause Any Other Problems?
Some claim that a high oxalic acid (oxalate) intake may be linked to the development of autism.
Some other claims have linked oxalic acid (oxalate)s to vulvodynia, a condition which is characterized by chronic, unexplained pain in the vagina.
Researchers have dismissed the relation between the aforementioned conditions and dietary oxalic acid (oxalate)s. However, a test was carried out on a group of 59 women with vulvodynia. A quarter of them experienced relief from the symptoms when they were put on a low-oxalic acid (oxalate) diet with calcium supplements.The authors of that study concluded that dietary oxalic acid (oxalate) might worsen, rather than cause, the condition.
Several online anecdotes do link oxalic acid (oxalate)s with autism and vulvodynia, but only a few studies have looked into possible connections. Further research is needed.
So we can say that even though some people have suggested that consuming foods high in oxalic acid (oxalate) may lead to autism and vulvodynia, but at this point the research does not support these claims.
Most food items with oxalic acid (oxalate) are very healthy
A lot of the proponents of low oxalic acid (oxalate) diets have cited the negative health effects of oxalic acid (oxalate)s and advised people to avoid food items that are high in oxalic acid (oxalate)s.
However, it’s not that simple. Many of these are healthy foods that contain important antioxidants, fiber and other nutrients.
Therefore, it’s not a good idea for most people to completely stop eating high-oxalic acid (oxalate) foods.
A lot of oxalic acid (oxalate) rich food items are delicious and provide many health benefits. Avoiding them is not necessary for most people, and may even be detrimental.
Your gut determines oxalic acid (oxalate) absorption
Some of the oxalic acid (oxalate) you eat can be broken down by bacteria in the gut, which happens before it can bind to minerals.
Oxalic acid (oxalate) also serves as the chief energy source of one of the prominent gut bacteria, Oxalobacter formigenes. It significantly reduces the amount your body absorbs
However, some people don’t have much of this bacteria in their gut, as antibiotics decrease the number of O. formigenes colonies
What’s more, studies have found that people with inflammatory bowel disease have an increased risk of developing kidney stones
This is partly because they are unable to regulate the amount of oxalic acid (oxalate) they absorb.
Similarly, elevated levels of oxalic acid (oxalate) have been found in the urine of patients who have had gastric bypass surgery or other surgeries that alter gut function
This indicates that people who have some kind of gut dysfunction or are consuming antibiotics, are better off with a diet low in oxalic acid (oxalate).
Foods High in Oxalic acid (oxalate)
While Oxalic acid (oxalate)s are found in all plants, the amount of oxalic acid (oxalate) content varies from plant to plant. Some might contain a lot of it, while some might only contain a little.
Here are some plant based food items that are high in oxalic acid (oxalate) content (100-900 mg per serving):
Beet greens
Rhubarb
Spinach
Beets
Swiss chard
Endive
Cocoa powder
Kale
Sweet potatoes
Peanuts
Turnip greens
Star fruit
How to do a low-oxalic acid (oxalate) diet
People who are placed on low-oxalic acid (oxalate) diets for kidney stones are usually instructed to eat less than 50 mg of it each day.
Here are a few tips on how to follow a low-oxalic acid (oxalate) diet:
Don’t consume more than 50 mg of oxalic acid (oxalate) per day: Build your diet with different types of animal and plant sources which are dense in nutrients but low in oxalic acid (oxalate) content.
Boil oxalic acid (oxalate)-rich vegetables: Boiling vegetables can reduce their oxalic acid (oxalate) content from 30% to almost 90%, depending on the vegetable (17Trusted Source).
Drink a lot of water: A minimum of 2 litres per day is essential for healthy individuals. If you have kidney stones, drink enough to produce at least 2.5 liters of urine a day.
Get enough calcium: Calcium binds to oxalic acid (oxalate) in the gut and reduces the amount your body absorbs, so try to get about 800–1,200 mg per day.
You can choose from the following list of food items that are rich in calcium but low on oxalic acid (oxalate):
Cheese
Plain yogurt
Canned fish with bones
Bok choy
Broccoli
Should you avoid oxalic acid (oxalate) in your diet completely?
If you are suffering from kidney stones currently, or have suffered from them before, you are better off with a low oxalic acid (oxalate) diet.
However, if you don’t have any medical condition as such and want to eat healthy, you shouldn’t avoid oxalic acid (oxalate) rich healthy food since the benefits far outweigh the drawbacks.
For most healthy individuals, oxalic acid (oxalate) is nothing to be concerned about.