What are oxalates? Oxalates are compounds that naturally exist in many food items. Often found in food considered healthy – such as spinach and almonds – oxalates can cause digestive issues.
Oxalates often give foods their bitter taste and are thought to be compounds meant to protect the plant from predators, such as ourselves (they aren’t doing a very good job, are they?)
The problem with oxalates is we cannot digest them. They pass through the gastrointestinal tract and can contribute to common gut issues such as constipation, gas, bloating, diarrhea, and more.
Oxalates also bind to metal ions and form precipitates, which can cause problems. In the case of calcium, this combination can result in kidney stones.
Most importantly, it’s a good idea to be aware of your oxalate intake. Foods that are highest in oxalates include:
High Oxalate Food List
- Sesame seeds
- Spinach
- Rhubarb
- Rice bran
- Bran flakes
- Almonds
- Miso soup
- Navy beans
- Beets
- Dark chocolate
- Berries
- Potato chips
- French fries
- Nut butters
You might be starting to get worried I’m going to tell you that you shouldn’t eat these foods, so let me cut right to the chase…
High oxalate foods are not a problem for everyone.
I’m not telling you cut these out of your diet, I’m only bringing to your attention an important factor that could explain your mysterious digestive issues. Especially for those with healthy, nutrient dense diets, oxalates could be the answer to your gut problems you’ve been looking for!
Should you worry about oxalates?
If you aren’t having issues with your gut and are generally healthy, you shouldn’t worry too much about your oxalate intake. Though if you’re the health-conscious type who’s adding handfuls of spinach to your smoothie each day, you might want to consider toning it back a notch – even if you don’t have any issues yet.
In general, those who are affected by recurrent kidney stones, gut issues, autoimmune disease, and other chronic conditions should examine their oxalate intake. If you have any of the following conditions, you might want to try scaling back you oxalate intake to see if it affects your health positively.
- Kidney stones
- Leaky gut syndrome
- Irritable bowel syndrome (IBS)
- Inflammatory bowel disease (IBD)
- Small intestinal bacterial overgrowth (SIBO)
- Autoimmune diseases such as chronic fatigue syndrome
- Nutrient deficiency (could be due to malabsorption)
- Chronic inflammation related diseases
- Vulvodynia is often caused by excessive oxalates
Bottom line is too many oxalates can mess with your digestion.
How do oxalates interact with digestion?
As a rule, you don’t want your body to absorb oxalates. If oxalates pass through the GI tract without causing problems, then they aren’t much of an issue. A major concern is when oxalates are consumed alongside a gut condition, like leaky gut syndrome, which could increase the amount of oxalates absorbed by the body.
Those with regular kidney stones have been found to have a higher rate of oxalate absorption. And probiotics have been shown to reduce the absorption rate of oxalates, probably through improved gut health.
Are there benefits of oxalates?
Oxalates are not completely understood, though studies suggest they could act like chelators – meaning they help prevent toxin absorption by binding to harmful substances.
Oxalates could also work like fiber. At one point in time we thought insoluble fiber wasn’t good for us because it couldn’t be absorbed. We now know there are many benefits to insoluble fiber, including bulking up stool and aiding in moving waste through digestion.
The uncertainty surrounding the exact nature of oxalates means you don’t need to over worry about them, though they are important to be aware of – everyone reacts differently to oxalates and you may or may not be affected.
Healthy eaters often have high oxalate diets
Those with high oxalate intake are usually eating a diet that is considered healthy, such a vegan, vegetarian, raw food diets, Paleo, ketogenic, and other low carb diets.
It can be incredibly confusing when those who eat really clean experience gut issues similar to those who are eating junk!
A review that examined oxalate intake of 240,681 individuals in three studies found the average oxalate intake is around 200 mg per day and about 40 percent of oxalates in a diet came from spinach.
To give you a better idea of how high spinach is in oxalates – just one cup of spinach contains 225 mg of oxalates! You can see how easy it could be to consume the average amount of oxalates.
Keep in mind, there is no recommended dietary allowance (RDA) for oxalates. These numbers are averages and by no means a recommendation.
Also, I’m not suggesting you should completely avoid high oxalate foods, everyone differs in their ability to pass oxalates through their digestive tract. Remember, the gut issues that come from eating oxalates are caused by the body’s inability to absorb and digest these materials.
Reducing the impact of oxalates
Up until recently, most people were only aware of oxalates if they struggled with kidney stones. But we are realizing oxalates can have other unwanted impacts on the gut.
If you consider yourself a healthy eater but somehow struggling with gut issues (maybe you also eat a ton of spinach), consider taking steps – similar to those with kidney stones – to reduce the impact of oxalates on your digestion:
- Avoid high oxalate foods (consume low oxolate foods) – A pretty obvious recommendation. In my experience, the biggest culprits here are spinach, almonds, dark chocolate, beets, nuts, and nut butters.
- Cook oxalate containing food – When you cook or soak oxalate containing foods such as beans and spinach, you reduce the oxalate levels. This is why those on an all raw diet may have an increased chance of health issues caused by oxalates.
- Heal your gut – Don’t suffer quietly with digestion discomfort! If you experience gas or bloating after eating, constipation, diarrhea or any other issue that occurs regularly, I urge you to make an appointment with your functional medicine doctor. When your gut isn’t working properly it can cause poor nutrient absorption, which can compound over time and cause a cascade of health consequences. When your gut is impaired it can make it more sensitive to oxalates and vice versa – too many oxalates can lead to impaired gut health. It’s all about that balance!
- Take Calcium with your meal – Calcium Citrate loves to bind with oxalates, which makes a larger molecule that passes through the digestive tract without absorption. Add more calcium rich foods to your diet, and if you can pair the two that’s even better. Try adding cheese to your spinach salad or enjoy a little Greek yogurt with your almonds and berries. You can also take Calcium Citrate 250mg per meal.
- Consider your vitamin C intake – For people with recurrent kidney stones, typically the advice is that you reduce or limit your vitamin C intake because it has been shown to increase the overall risk of developing kidney stones.
However, studies have demonstrated that vitamin C may increase the amount of oxalates you excrete in your urine. So, it may be beneficial for reducing oxalates in your body overall, especially if you aren’t affected by kidney stones.
If you’re struggling to put your finger on the cause of your digestive issues, you should consider oxalates. In my experience, those with extremely healthy diets (high in spinach) are the number one cause oxalate issues.
Could oxalate reduction be the solution you’ve been looking for?
Share this article with a friend who just loves to add spinach to everything – Oxalates could be causing them digestion issues!
Resources:
https://kidneystones.uchicago.edu/how-to-eat-a-low-oxalate-diet/
https://www.ncbi.nlm.nih.gov/pubmed/8335871
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5300857/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3541088/
http://jasn.asnjournals.org/content/18/7/2198.long
https://my.clevelandclinic.org/health/articles/kidney-stones-oxalate-controlled-diet
https://www.ncbi.nlm.nih.gov/pubmed/12631089
Since calcium binds to oxalate shouldn’t a person that is at risk of having kidney stones be avoiding calcium? Calcium oxalate stones are the most common type of kidney stone. I’m confused.
Unlikely… Calcium will bind the oxalate that causes kidney stones so it may decrease risk
I was eating lots of spinach smoothies with cucumber celery, carrot, pineapple and started getting sick afterwards. This last time I actually vomited it up. I switched out the spinach.with kale and still had similar issues. Thought kale was low oxalate.
Trying to figure out how I can still get green smoothies in since that’s been so helpful for me getting in more veggies
Yes, you may need to alternate or avoid oxalate
Thank you, Dr. Carnahan. I appreciate your blog. After much research, I have noted that every list of low and high oxalate foods is different and conflicting, and it leaves me perplexed and nervous about eating. Who has the most accurate list?
I suggest speaking with a registered dietician to personalize your diet. I don’t recommend eliminating oxalates entirely as they are in many very healthy foods. If you have an issue with oxalates, best to deal with root issue in body first.
I don’t disagree with anything in your article, I only have some debate.
A better answer might be find me a food that doesn’t have any oxalates or sulfur, as these two guys run together, you take one out you put one in, or one steals or trades one for the other. Thanks for the B6 article, as B6 well .. sort of chelates oxalate, molybdenum chelates sulfur. The tide might be turning on vitamin C intake, kidney stone theory, but I doubt it. Certainly the ascorbate goes through the kidneys.
http://orthomolecular.org/resources/omns/v09n05.shtml
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5981254/
Oxalates could be causing allot of things, not just renal, but what runs with oxalates that comes with vegetables?, some kind of chemical application.
https://www.westonaprice.org/health-topics/vegetarianism-and-plant-foods/the-role-of-oxalates-in-autism-and-chronic-disorders/
You mentioned that cooking foods will lower oxalate levels and specifically mentioned beans and spinach. I understand that beans have to be pressure cooked to reduce oxalate load, and that it doesn’t lower the load by much. However, cooking spinach actually increases oxalate in spinach – it jumps from 656 mg per full cup for raw, to 755 mg per half cup for cooked. And juicing increases oxalate load in all fruits and vegetables, even in the presence of calcium (see link). https://www.amjmed.com/article/s0002-9343(13)00390-2/fulltext. I’ve been learning this lesson the hard way. I’m a reformed juicer with subsequent kidney damage from high oxalate juice, and that doesn’t mean just spinach as mentioned in this article – carrots, kiwis, dates, and raspberries (as well as others) are all high in oxalate. I was in serious disbelief when confronted with this reality by a nutritionist several months ago. I thought I was eating so healthy, but I was not. 🙁
Thanks so much for sharing this helpful information, Christine!
Does Sophora japonica (used in Quercetin supplements) have high or low oxalates? Apparently, these supplements are useful for low histamine diets.