Have you ever heard that certain leafy greens need to be cooked before eating?
Do you wonder why?
Nutritional powerhouses like kale, collards, spinach, chard, and beet greens all contain oxalic acid. Oxalic acid occurs naturally in many fruits and vegetables, but when it comes to leafy greens, it’s present in higher concentrations.
The problem with oxalic acid is that it binds with calcium and other minerals (like magnesium and iron) in order to be excreted from the body.
Calcium and magnesium are precious minerals our bodies need to function and grow properly. We are generally low or deficient in these minerals because modern-day agriculture practices have led to mineral-depleted soil. If we eat raw kale or other leafy greens raw, we just further the problem.
However, you don’t have to give up these delicious, dark green leaves completely. Oxalic acid is easily reduced by steaming, boiling, or wilting the leaves of any of these vegetables for 5 to 8 minutes. Gently squeeze out any remaining water from the vegetables, and continue on with your favorite recipes. Also, dump the leftover water, because oxalic acid leaches out of the leaves and into the surrounding liquid.
Do you love your morning green smoothies? Simply cook and dehydrate your favorite greens, then turn them into a powder in your blender. Store the powder in a sealed jar and add it to your morning drink for that nutritional boost. Your beloved morning routine lives on. 😉
Here are a few of our favorite dark leafy green recipes.
You can also ferment greens to reduce the oxalic acid, such as in this fermented lemon spinach kraut.
Do you love your greens? How do you work around the oxalic acid issue? What’s your favorite way to reduce before consuming dark leafy greens?
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Hey, great blog post! I was wondering, does dehydrating kale get rid of oxalic acid, or does it need to be cooked?
Kristina, it needs to be cooked first.
Hi Katie, thanks so much for this info, my husband has a cancer scare and we’re juicing etc. I tried to open Simply Foody but can’t find it anywhere?
http://www.realfoodforlife.com/oxalic-acid-controversy/
Great info! Up until last year I didn’t know much about this. My husband is especially prone to kidney stones and has to be very careful of dark greens.
What about for juicing? Can you tell me how to work around this?
Does this also pertain to lettuce?
Some people like to steam a bunch of kale/spinach/etc., chop it up and freeze in ice cube trays, and then pop the frozen cubes into a storage container. The cubes are then ready for their smoothies.~
Do we have to cook all greens and how long can they be frozen?
Lois, I have never juiced kale or any other green for that matter. But to reduce the oxalic acid, it would need to be cooked first.
What about lettuce? I really want to continue juicing greens. . . so looking for a good solution.
Lettuce would be perfectly fine to juice.
If I cook kale by making kale chips, does that reduce the oxalate acid?
Do you know if oxalic acid or the goitrogenic effect of these greens is reduced when baked or roasted, such as with kale chips? Thanks!
Lindsey, while not 100% positive (because I haven’t tested it in a lab) I would think that baking greens would reduce the oxalic acid. Assuming the temp is higher than 300 degrees Fahrenheit.
I didn’t cook my kale but simply dehydrated it. I figure this still does some good in reducing the oxalic acid. What do you think?
What temperature did you dehydrate the kale at? I tend to dehydrate all of my vegetables and fruits at temps 110 or lower. In this case the oxalic acid would still be intact.
I don’t know but it was a food dehydrator so I think they are set fairly low. That is too bad; I was hoping it would make a difference with the oxalic acid piece.
You are completely wrong. Dehydrating does nothing to reduce oxalic acid content. You MUST boil kale, then dehydrate the boiled kale.
I wonder if this is why most kale chips taste like dirt to me. I will need to experiment.
Now I make a kale salad by salting it and massaging olive oil into it. This wilts the leaves and makes them taste not like Kale. I’ve also done it to collard greens. I wonder if this reduces the oxalic acid.
A massaged kale salad (or collards) would still contain the oxalic acid if not cooked. I *love* raw massaged kale salad, but I do limit myself to it only once or twice a year because of this very issue.
My understanding is that oxalates are less a concern with kale and other crucifers than the goitrogens and how they can affect the thyroid. Other sources have suggested steam time of 3+ minutes for spinach and 4+ for kale. If you have a concern with those anti nutrients, you might need to steam them at least that long. We have no health issues; I steam my spinach 2 mins and kale 3 mins.
Would wilting them directly in a frying pan rather than in a steamer basket work? Or is it a necessary step that water is drained off them? I like to cook them down in stir fries and soup but don’t separately steam first. Should I?
Lynne, you want to drain the water.
This is depressing. So all those fresh spinach salads I’ve been feeding my family for the past several weeks from my husband’s organic garden are bad for us? And the kale in the freezer that I want to just throw into soup will leach the bad stuff into the soup broth. Dang.
What about baby kale? Probably contains less because it is smaller? It certainly is easier to chew raw when it’s still young!
This is great info! We already know this but it’s so nice to have a link we can easily share with people so they understand. We’ve got it set to post on our paleo meetup group page and Clint can now send his clients this link, so thanks 🙂
This is actually not true!!! If you are interested in a scientists take on these ‘problems’ with raw greens check out Foundmyfitness.com. If you are not a scientist or nutritionist you should not spread incorrect information!!
I did research and found the original post that Victoria Boutenko sent out months ago which I had forgotten about. The problem is kidney stones. If you don’t have a family history or problem with them raw foodists (I found others) say NOT to worry. The benefits of raw out way the other. Also, rotate greens. I’m going to continue with my green smoothies and not worry about it. Just wanted to make sure I was doing the right thing.
Would it be a good idea to use the water from steaming to water plants in the garden?
Then why on earth do all the raw foodists tell you to eat RAW greens every day for the most benefits? Is oxalic acid that serious of a problem?
Yes, I want to know this answer too.
Since I was young I would get horrible joint pain! As I got older it became worse! The more greens I ate the worse it became! I thought eating healthy would help! I heard a guy talk about oxalates and bam that was the answer! Stop greens no more avocados stopped nuts! It’s a big list! Started eating meat and only meat and pain went away after around 2 weeks! 30 years of pain! Last horrible!
Thank you for your efforts and successes in changing the way Americans think about food.
Okay, let me make sure I’m not confused. Fermenting aside, all dark leafy greens must be steamed only, if you wish to remove the oxalic acids? I have been making sauteed kale in my good ole cast iron skillet forever; I was under the impression that cooking them was all that was needed to neutralize oxalic acid.
I saute in coconut oil, with perhaps just enough water to create a little steam and facilitate faster cooking. Are you saying I should steam them FIRST, throwing out the water below them, and THEN cook them my normal way?
Thank you,
Michelle
Michelle — Yes, they should be steamed and the liquid drained. Then toss with your coconut oil and seasonings. 🙂
Thanks, Wardee. And also for the Kombucha/tannins answer.
yes, what is the answer pls. I already have bone loss and now this scares me a lot!
Also – slightly off topic, but the WAPF article link also mentions tannins in tea being anti-nutrients. When we use tea for Kombucha brewing, we aren’t draining off that water, so, do the tannins still remain?
Thanks again ~
MichelleB
Michelle — That’s a great question. My understanding is that the fermentation reduces the tannins, no draining required. 🙂
I use kale, chard, and spinach in smoothies, but to aid in reducing the amount of oxalic acid available to be absorbed by the body, I also add citric acid (from lemons or limes) and milk or almond milk (for additional calcium). Research has shown that both citric acid and calcium help to make the oxalic acid unavailable for uptake by the body, thus reducing the amount of oxalic acid absorbed.
I steam vegetables from time to time and like the idea of it, but the water in the pot under the steaming basket turns green from leaching out the green vegetables. Is this removing nutrients from the greens? When I cook in water, I use minimal water and drink the water after cooking.
I really love these greens in salads. Obviously, once cooked, they no longer work for salad greens. Any way around that? Anything you can do to counteract the effects of eating them raw? Which leafy greens are okay to eat raw?
I read this article and the comments on the same day I made my first raw spinach containing smoothie ever. That’s such an incredible coincidence, it has to be a warning sign from the universe.
Thank you all!
I have enjoyed your many helps in cooking healthy, but this information about raw spinach has puzzled me completely. Below is an excerpt (page 63) from the book Fresh Vegetable and Fruit Juices by N.W. Walker D.Sc.known world wide. Please explain! – I am looking for referenced information, if at all possible, to help me understand why Dr. Norman Walker would not agree with cooking (steaming) spinach at all. Thank you so much!
“..Live Food means that food which contains live organic atoms and enzymes found only in our raw foods.
We have in previous chapters, covered this important question of organic versus inorganic atoms in our food. It is very vital to stress this matter in regard to oxalic acid. When the food is raw, whether whole or in the form of juice, every atom in such food is vital ORGANIC and is replete with enzymes. Therefore, the oxalic acid in our raw vegetables and their juices is organic, and as such is not only beneficial but essential for the physiological functions of the body.
The oxalic acid in cooked and processed foods, however, is definitely dead, or INORGANIC, and as such is both pernicious and destructive. Oxalic acid readily combines with calcium. If these are both organic, the result is a beneficial constructive combination, as the former helps the digestive assimilation of the latter, at the same time stimulating the peristaltic functions of the body.
When the oxalic acid has become INORGANIC by cooking or processing the foods that contain it, then this acid forms an interlocking compound with the calcium even combining with the calcium in other foods eaten during the same meal, destroying the nourishing value of both. This, results in such a serious deficiency of calcium that is has been known to cause decomposition of the bones. This is the reason I never eat cooked or canned spinach.
As to the oxalic acid itself, when converted into an inorganic acid by cooking or processing the food, it often results in causing inorganic oxalic acid crystals to form in the kidneys.” (Fresh Vegetable and Fruit Juices – Page 63 by N.W. Walker D.Sc.)
Much depends on quantity of spinach and/or kale you consume, I think. My personal belief is that plant foods work synergistically and that the relatively small amount we use in our smoothies is likely not a concern for healthy people. Juicing, if using huge amounts of greens, may be another story (I don’t juice). Probably why juices contain other fruits and veggies along with greens.
Another note, from a blog post on Donna Gates’ body ecology.com: “According to Owens, low oxalate vegetable options include kale, mustard greens, and collard greens. Owens has found that boiling vegetables significantly reduces their oxalate content. For example, kale that has been steamed has an oxalate content of 8.8 mg, whereas the same amount of boiled kale contains 4.9 mg. That’s a 40 percent reduction!”
It’s a conundrum. You lose nutrition while getting rid of possible anti-nutrients. That’s why I apply the ideas of everything in moderation, and rotate your greens.
Does culturing your vegetables take care of this problem? What does culturing do to the oxalates?
Hi everyone, I know this thread has been going on for a while but I just discovered it. If anyone is interested (e.g. Laura and Ann may be judging by their last posts) fermenting raw kale does lower the oxalic acid, so you get the benefit of the raw “live” food while eliminating the problem of the oxalate. Relative to some other green leafy vegetables kale is quite low, but I eat loads of kale so this is a good way to do it!
In case you don’t know how, you make it just like you would sauerkraut, just replacing cabbage with kale (although I mix both!!).
Hope that is useful!
Mary 😉
Not only does steaming reduce the oxalic acid, it also INCREASES nutritional content in cooking/fermenting veggies. In order for our bodies to maximize the nutrition from food, we need to get ALL of it from cooked, NOT overcooked, foods.
Does steaming reduce getting gas from Kale?
My understanding is that oxalic acid in the urine reacting with calcium in the urine produces the very insoluble calcium oxalate in-situ, which can then end up as kidney stones. I would guess that if oxalic acid were to form the insoluble calcium oxalate BEFORE we ingest it, that then the insoluble calcium oxalate would not enter our blood or urine to begin with. Hence I throw my kale in a blender along with some calcium supplement pills, and then use it in vegetable soup that I cook for over an hour. My theory is that this will promote the reaction from oxalic acid to calcium oxalate before we eat it, making it safer. DISCLAIMER: I have a little background in chemistry, but none whatsoever in medicine or nutrition.
That is a good idea, yet kale contains very little oxalic acid. Actually less than 10% than that of lettuce! Source :USDA food list : http://ndb.nal.usda.gov/ndb/search/list.
Thanks for the information – i never cared about that, but I think it makes sense to check Calcium (in the whole blood, not in the serum !!)
Cream and milk – I think the Casein – is able to bind oxalic acid – but this cannot be the solution…
On the other side , the healthy Sulphoraphane is no longer availabe when heatet …
not easy…
here I found good information:
https://www.oxalsaeure.net/zubereitung-lebensmittel/
How about adding magnesium hydroxide or citrate. By the way Kale has only 0.02 grams of oxalic acid per 100 grams.
Just started learning more about oxalic acid and its related potential health issues.
How long do you have to cook it to deactivate, or get rid of, the maximum amount of oxalic? Or would that depend on if it was steamed vs sauteed and at what temps etc?
I plan on cooking a big batch of spinach or kale etc at a time and freezing it in portions to use in cooking or for my smoothies.
Kale actually has very low oxalate levels. 50 times less than spinach.
First of all, it is very difficult to get accurate information about the oxalate content of kale, hence people getting different values. I think the most accurate information is that it it fairly high. I see alot of incorrect information on the internet, but people with a history of kidney stones should limit the amount of oxalates (not avoiding raw kale completely but limiting it and avoiding spinach and chard completely), drink alot of water (2-3 liters daily), and consume lemon or orange juice daily. I think the information in this article is accurate and quite helpful for people with a history of kidney stones. Im a retired dietitian.
This post is misleading. Please look at Dr. Greger’s posts about oxalates and goitrogens on NutritionFacts.org if you’re interested in these subjects. To the author: It is really disappointing that you didn’t caveat your post above appropriately. People in the comments are now afraid to eat salads, which really doesn’t help the sorry state of nutrition in the western world. Further, cooking, then dehydrating and powdering your greens is a bit excessive. You are making your own processed food and telling everyone to do the same. Health doesn’t have to be hard. Drink plenty of water and eat a large variety of fruits, vegetables, whole grains, beans, and nuts every day. If you’re concerned with oxalates because you juice twice a day or have a history of kidney stones, then you can focus on some of the changes the article outlines. The general population, barely eating vegetables as it is, doesn’t need a reason not to do so. Finally, the facts above also leave something to be desired. Kale is quite low in oxalates, for example, and shouldn’t be grouped here. I hope this post helps someone eat another salad and do their own research.
Hello and thank you for your comment, Kayla.
Dark leafy greens doesn’t include lettuces, so please everyone… eat up on your salads!
Regarding kale, while it might contain less oxalates than spinach (for example)… I suppose if one eats it occasionally, that might not be as big an issue.
However, the trend is that people eat great big piles of dark leafy greens, as kale chips or in green smoothies. That’s more quantity than a salad would have. It all adds up, so we stand by our recommendation that it’s best to pre-steam kale.
If someone wants the benefits but doesn’t want to go to the trouble of pre-steaming… there is a fermented kale powder available right here (fermenting also reduces oxalates).
It’s not our intention to discourage people from eating vegetables… just to point out the dangers of consuming dark leafy greens, especially in large quantities, without being smart about preparation.
Thanks again for your comment, and I hope this clears up any confusion as to our intentions or recommendations.
What is a large amount of greens per day? I have a smoothie every morning with raw kale or spinach about a cup full is that too much?
This is fantastic information as I literally just bought a case of these pre-cooked collard greens called Rosey Bloom’s. They are delicious, hence me stocking up, but when i ran across this article i got worried. But they are already cooked (steamed i think) and seasoned so i think i avoided the Oxalate overload. This is great information…Thank you!
The Greek islands are in the ‘blue zone’ of a few of the places on earth that enjoy some of the best health.
One staple in their diets is ‘horta vrasta’ – essentially boiled wild greens – dandelion, chicory and spinach tend to be what is used, but in essence: any greens – they are boiled down and consumed with plenty of olive oil and lemon juice.
The preparation reduces oxalates (& other anti-nutrients) plus eases digestion and absorption of the nutrients.
It is interesting that another commentator pointed out the use of citric acid in oxalate reduction – which is true – and noting the use of lemon juice in horta!
I soak my greens first, then boil for five minutes or so. Topped with EVOO, lemon juice and feta cheese is delicious!
Vegetables, grains, legumes, seed and nuts all require proper preparation.
Raw is NOT always better or healthier.
Thank you for the article.
Does baking reduce the oxalitic acid ? I make kale chips with mine by tossing in avocado oil sprinkling with Himalayan salt and baking at 275 for about 20 min. The leaves do wilt as they dehydrate but there is little to no liquid like there is in boiling.