Sharing an article on Rhubarb leaf today, because I like how the guy thinks. Just because a claim is made means nothing if the research isn’t quoted with accessible sources, or understood in the balance of how the food might be eaten and in what quantities. When making claims ALWAYS include sources that people can easily access! Just parroting warnings with nothing to back them up often results in the parroting of fear-mongering because of a study that was taken out of context.
I, perhaps like many others out there, had been parroting the claim that Rhubarb leaf is dangerous for you, having had such a discussion just days before the reading of this latest research. Much like discovering that Mountain Ash berry is actually useful rather than poisonous as I’d been taught growing up, this discovery sets me straight on what now appears to be an old wives’ tale born out of poorly understood anecdotal stories that led to research papers taking things out of context. Much like what happened with the Canadian government banning all but two Genuses of Comfrey for sale in the country, because of studies showing rats dieing from ingesting far more comfrey per body weight than humans would EVER do! (seriously, eating a large mixing bowl’s worth of comfrey leaf in one sitting is quite the exageration to prove fatality if ingested!) Pyrralizadine Alkaloids in Hound’s Tongue and Viper’s Bugloss have similarly exaggerated food intake over the course of 6 months before it will kill you! You are far more likely to experience tachycardia and/or intense anti-depressant activity long before you reach fatal liver damage with those two herbs. But governments, pundits, and those who quote them without quoting their sources, get this stuff blown out of proportion and then we get warnings that no one can trace that we find out later, were poorly documented or based on faulty interpretation of the research, or both.
The author of today’s rhubarb link, debunks the oxylate issue, while leaving the door open to other compounds that might exist in the leaf.
One of the books I’ve downloaded, Prescription for Nutritional Healing by Phyllis A. Balch, 6th edition, mentions Germanium in Rhubarb, that has been known to cause toxicity if eaten in enough quantities, and notes that Germanium has been known to cause kidney trouble, but there again, it’s not merely claiming toxicity, but “in enough quantities”. In her juicing section, she suggests removing the greens of carrots and rhubarb “as they contain toxic substances” but does not quote any sources for this claim. Her book was published by Penguin Random House copyrighted 2010 and 2023.
Germanium itself, discovered in the late 1800’s by a German researcher, has been researched and shown to be of benefit to the human body on a number of levels. I grabbed a few sources and updated my database to reflect that. As with all trace minerals, a little goes a long way, don’t overdo it. So my question becomes, it is the oxylate in the leaf or the Germanium in the leaf being labelled a culprit here?
Most other sources I’ve come across, don’t give research data to back themselves up on the toxic leaf question. In fact, going to historical sources from the late 1500’s (16th century), decry other sources claiming that Rhubarb and it’s domestic family didn’t become garden herbs until the 17th century. Both Culpeper and Gerard will contest that claim, as both of them published books in the late 1500’s stating that many members of the Rhubarb family already existed as garden herbs. Gerard in his book: Gerard’s Herbal, takes the history of Rhubarb back further than that, to writings of Pliny the Younger.
“The dock is called in Latin, Rumex, and Lapathum; yet Pliny in his 19th book, 12th chapter, seemeth to attribute the name of Rumex only to the garden dock.”
Pliny the Younger lived during the days of Ancient Rome.
The various docks are all members of the buckwheat family, known as Polygonaceae, of which Rumex (curly, yellow, etc, dock) and Rubicaea (rhubarb) are members.
These older books talk about taking the leaf as a drink to help with cleansing the colon, aiding in constipation, dealing with Jaundice (liver), and as a diuretic. Most other sources today will only mention the root for some of those uses.
If you have kidney issues and don’t typically eat rhubarb or other high-oxylate foods, the following quote from Healthline may be of interest:
“growing evidence suggests this problem is worse for those who lack certain beneficial gut bacteria. Interestingly, some gut bacteria, such as Oxalobacter formigenes, degrade and neutralize dietary oxalates.”
Note again that their only claim to leaf toxicity in their article, is the level of oxylate in the leaf mentioned earlier prior to this quote.
It is known that oxylates bind to Calcium, but it’s also known that various plants containing oxylates also contain calcium. If your diet is low in calcium, you may need to boost that when enjoying oxylate-containing foods.
It is refreshing to have tripped across this guy’s blog article, giving some context to the leaf claims and comparing them to the data given about other foods containing levels higher than Rhubarb, yet eaten far more frequently and commonly more accepted. Even better, he gives multiple sources to allow for further digging.
Oxylates do have a place in the human diet and in food as medicine, but the saying applies: All things in moderation!!! Oh, and eat your antioxidants!
EDIT April 7, 2025
Further to the above discussion, and due to discussions in person and in a questionable herbology textbook my daughter is currently having to review for her herbalist certificate (this thing is written using 18th century-style english and grammar, while westernizing taoist medicinal teachings (vital force instead of chi, same concept otherwise), giving incredibly harmful dosage amounts for many recipes) and she most recently ran across them talking about the root of chinese rhubarb versus garden rhubarb. While it turns out in her digging that the roots of both types of Rhubarb have the same compounds, she also ran across further information in the discussion on eating the leaves.
The debate over the safety of rhubarb leaf goes back at least to 1919 when the following “letters to the editor” show up in The Journal, Aug. 23, 1919, p. 627:
The note in the bottom right about cooking, is of interest. The note in the second to bottom paragraph regarding the ability of the stomach to break down calcium oxalates into their poisonous counterparts, is also of note. If the stomach isn’t breaking it down, it enters the small intestine where it enters the blood stream and gets filtered by the liver and the kidney. The stage in the liver is where many oxalates are oxidized, however, eating your anti-oxidants has been a known pairing with oxalate-containing foods down through history. Everyone loves strawberry rhubarb pie, however, a) the pie has been baked, cooking and thereby denaturing the oxalate content, and b) strawberries are a known anti-oxidant.
A study published in the Journal of Food Composition and Analysis, Volume 94, December 2020:
Oxalate bioaccessibility in raw and cooked rhubarb (Rheum Rhabarbarum L.) during in vitro digestion found the following when it came to cooking rhubarb stalks:
” Oxalate content in raw rhubarb has been well established; however, the levels of oxalate in cooked rhubarb, the most common way rhubarb is consumed, are rarely reported. Depending on the cooking method used, the amount of oxalates and the ratio of soluble to total oxalate remaining in cooked food may vary (Chai and Liebman, 2005).”
The paragraph below makes an incredibly important note about study methods, because it is often assumed in the world of vegetarian and vegan lifestyles, that nurtition available in food is automatically available to the human body, which isn’t always the entire truth or capacity of the body to unlock. Bioavailability is a necessary discussion that can’t stop merely at the nutrient compounds observed in the food.
“Many chemical methods have been used to measure oxalate in undigested food (Nguyễn and Savage, 2013b; Siener et al., 2016; Huynh et al., 2020); however, it should not be assumed that the soluble oxalate available for absorption in undigested food is equivalent to that of the same food after biological digestion in the gastrointestinal tract. It is important to use a digestive model that simulates the biological conditions to give a clear understanding of the processes involved.”
“… introducing higher fibre in the diet would also significantly reduce oxalate absorption by producing a fibre-mineral-oxalate complex that may be more difficult to be broken down than an oxalate-mineral or fibre-mineral bond (Nguyễn and Savage, 2013b).”
“Cooking significantly reduced (p < 0.05) the total and soluble oxalate contents compared to those of the raw rhubarb. The mean reduction of total oxalate in the three cooking trials was 49.7 %.”
“If a high amount of oxalate is trapped in the fibre fraction (pomace), this would lead to less oxalate being available for absorption.”
As compounds such as oxalates have been found both in the leaf and in the stalk of rhubarb, and as the leaf has less oxalate content than carrots or spinach, anyone who is concerned about the potential of oxalate stones in the kidneys, should cook their high-oxalate foods and be sure to pair them with anti-oxidant and high fiber foods.
This could very well be the reason that it became tradition to serve carrots warm, with a pat of butter. That is your high-fat dairy product being given alongside your high oxalate food source in a way that is cooked. You might remember how strawberry-rhubarb pie often comes to you with a dollop of whipped cream or ice cream on top. There is your dairy fat again.
As a result of these findings, you can lower not only your risk of oxalate damage from rhubarb, whether it’s the leaf or the stalk, but also from that of other “high-oxalate” foods, by doing the following:
- Cook them, whether in a pot such as for carrots or wilted spinach greens, or in soups, stews, pies, cooked puddings such as carrot pudding, etc.
- Pair them with anti-oxidant foods of which there is a very long list to choose from, ie: blueberries, strawberries, apples, black pepper, hazelnuts, oats, mushrooms, cherries, turmeric, etc.
- Cook them in or pair them with dairy fats, the closer to whole-fat the better such as butter, cream, whole milk.
Suddenly that rhubarb pie with ice cream makes far more sense than merely a delight to the taste buds!
end edit
