I read (and commented on) a post over on Healthy Home Economist yesterday about oxalates (find it here). As of this writing, it is now the most-commented post on her site. While I was surprised and saddened by the outrage that was pouring out in the comments section, I was grateful to see that the post was making an impression on many. You see, if a post makes an impression, then people will remember it. Then, when they run into issues years down the line, hopefully some small niggling memory will remind them of what they read, and trigger an Aha! moment for them.
But I digress…What I wanted to do for that post was back it up with some science and numbers. Because the only valid criticism I saw among all the venom that was being spewed, was that Sarah had only cited one source on the WAPF (Weston A. Price Foundation) website for her information (and that source, when I checked it, did not cite any research to back up its claims). So I set out to do some corroborating for them. Please note that I am neither a medical professional nor a Registered Dietitian. I’m just someone who has had to learn a LOT about oxalates over the past couple of years.
Before I Jump Into the Science
First, though, I wanted to address some of the worries that cropped up. I think some people were skimming her article (or worse yet, just reading the headline), and not paying attention to the truly important information given in it. When she specified that 20% of people can have gut integrity issues which cause them to be susceptible to oxalate problems, the implication is that a whopping 80% of people DON’T have such problems. The trick is knowing in which group you fall. If you don’t know which group you’re in, for goodness’ sake, at least please pay attention to your body’s signals! While oxalates can easily sneak up on you, as they did on me, knowing that what you eat has an enormous impact on your health makes all the difference. It’s something that hadn’t yet sunk in for me (up until then I had always been able to eat almost anything with relative impunity), but I promise you it’s true.
Likewise, if you already know that your gut health is suspect (and for many folks who frequent Sarah’s site, I believe this is the case), then limiting your oxalate intake is a wise move, at least until you feel with some certainty that your gut is healed.
And a Bit of Refutation
Here’s the thing, I’m not totally agreeing with Sarah. She got a lot of things right, but she also got a few wrong. I can’t say why for certain, but it’s a fair bet that she may not have the latest testing numbers on oxalates available to her. For example, she warns against using most all leafy greens in your smoothies, including kale, which is particularly low oxalate (especially when compared to spinach). This is throwing the baby out with the bathwater, as you’ll see below.
Another thing I saw a lot of folks take issue with was her use of words like “large amount,” rather than specifying weights or measures. So let’s go with common sense: a serving is generally measured as a half cup. Since most green smoothies contain multiple half-cup servings of greens, her assertion of “large amount” makes perfect sense.
For reference, here are the oxalate values of a half cup of a few leafy greens (rounded to the nearest whole number), as per the latest available testing. A more complete list (with sources) is available via the TLO group, if you are desirous of such edification.
|Leafy Green||mg Oxalate per 1/2 cup serving|
|Raw Baby Spinach:||159|
|Boiled Dino Kale (raw values not available):||2|
|Boiled Mustard Greens (raw values not available):||3|
|Raw Swiss Chard:||175|
|Raw Red Rib Dandelion Greens:||10|
|Raw Collard Greens:||4|
|Raw Romaine Lettuce:||1|
As you can see, not all greens are created equal in terms of oxalate content! So it really pays to know which greens you can add to your smoothies on a regular basis without fearing their oxalate content. Of course, rotating and eating in season is also an excellent idea, and I have other issues with smoothies as well (I don’t think pre-chewing food is good, except in cases of medical necessity), but I do believe that the average American can use an extra serving of greens, so I’m not going to go to great pains to dissuade folks from getting it in this fashion.
Now for the Science
First up: “a high oxalate diet can contribute to some very serious health problems particularly if you are one of the 20% of people (1 in 5) that have a genetic tendency to produce oxalates or if you suffer from candida or other fungal challenge.” Who are these 20% of people? To be honest, I’m not sure where the WAPF got that specific number and their claim that it is a genetic variance, but I can find some studies that at least make it plausible when you add in fungal infections, as Sarah did.
As regards the genetic component, this study found that roughly .000015% of the population of the Netherlands has Primary Hyperoxaluria Type 1 (PH1). Granted, they aren’t representative of the world, but it does help me realize that we’re not going to get anywhere close to 20% of the general population with PH1. This study notes that there are only 24 patients noted in the literature as having Primary Hyperoxaluria type 2, so again, we’re not going to get our 20% from that disease either.
That leaves “candida and other fungal challenge.” Since this study managed to culture various candida species from oral swabs of 63% of middle-aged and elderly participants, I’d guess that finding a fungal challenge in 20% of the general population would be a fairly simple matter. And can fungi produce oxalates and release them into a host? Can they ever! This paper is one of many which demonstrates that rampant damage that aspergillus niger can do via oxalate crystal deposition.
Next up, let’s take a look at this sentence: “Oxalates can be deposited almost anywhere in the body and wherever they land, pain or worse is the result.” and the later “Oxalate stones can show up in any body tissue including the brain and even the heart.” with which more than one commenter took issue. It’s not the first time I’ve cited this study, but here’s the most striking evidence from it: “At post-mortem examination severe nephrocalcinosis, with widespread calculus formation and
deposition of oxalate in the myocardium, testes, muscles and bone, was demonstrated.” In case you’re not familiar, “myocardium” means heart muscle. I’ll admit I can’t find any peer-reviewed papers which cite hard evidence of oxalate deposition in the brain. However, it has been speculated that oxalate can cross the blood-brain barrier and cause issues. It’s also been demonstrated in vitro that rat brain cells have transporters for oxalate. If this is true, presumably tissue deposition in the brain would not be too great a leap, but I admit we need more science done on this. Problem being, most people with known oxalate issues aren’t going to be too keen on having tissue samples taken from their brains! So we sort of have to wait for people to die, AND just happen to have it be noted that oxalate deposition has occurred in other places AND have the examiner also check the brain for oxalates. A bit of a long shot, but I hold out hope.
Here’s another bit I take a little issue with: “Given that the majority of people today suffer from gut imbalance/fungal issues caused by antibiotic and prescription drug use along with consumption of processed foods, a high oxalate diet which includes green smoothies is an unwise practice for virtually everyone.”
There is only a small body of evidence about this one, with this study among them. While this doesn’t provide support for her claim that “a majority” of us suffer from fungal issues, it at least acknowledges that such issues are rapidly increasing. Still, it has been my personal experience that many doctors don’t know about, much less look for, the fungal overgrowth which can be caused by antibiotics. Since antibiotic overuse is a known problem, though, I am hopeful that this will eventually become much more common knowledge. I only fear that if doctors DO become aware of it, they will see antifungal medication as the sole option, rather than allowing for natural, food-based healing as preached by Sarah and others.
What about the claim that “oxalates are extremely stable”? Well, we see they are heat-stable, and once bound to a mineral, do not readily dissolve in water. For all intents and purposes, this means that the oxalate which is in the food when it is harvested, will still be in it when it goes in your mouth.
In addition, as I mention in my article on soluble vs. insoluble oxalates, boiling can sometimes lower the oxalate content of a food, but not always. And you must also take into consideration that a boiled half-cup is generally much more dense than a raw half-cup, at least when it comes to leafy greens. So there’s no “getting away with” more spinach just because it’s boiled.
So Should You Really “Skip the Green Smoothies?”
In all honesty, I think the biggest problem with Sarah’s article was semantic – it did sound a bit sensational, but that is what makes it a good, attention-grabbing blog post. In fact, given how dry my own tone tends to be, I applaud you if you’ve managed to make it this far in my own article.
What I’ve posted above hopefully demonstrates to even the most hardened critic that yes, oxalates can be devastating to health. That doesn’t mean that they are devastating to everyone, in all cases. Knowing your own level of health and gut integrity is indispensable when determining how much of a given toxin your body can handle (and yes, oxalates ARE a toxin).
If you’re one of the lucky few with tip-top gut health (as well as your overall health), then an occasional oxalate-ridden treat is unlikely to cause any long-term damage. The real question, then, is how certain are you of your gut health? Does your gut have adequate stores of oxalobacter formigenes, or have you ever taken antibiotics (which kill this important microbe)? Do you have sufficient populations of other microbes shown to degrade oxalate? I encourage you to do your own research, and make your own conclusions.
Of course, it would probably be much simpler to stick with low-oxalate green leafies in your smoothies, and be happy with the health benefits you can reap from them.
Did I miss any points you’d like to see the science on? Feel free to leave me a comment and I’ll do my best to find it for you!