Rhubarb poisoning not from a rube
Some time ago, ScienceSunday shared a collaborative post about potato poisoning. http://goo.gl/80fdM Taking a break from my imaging posts here’s some information about rhubarb toxicity.
When we first planted our rhubarb in the garden we were told not to eat it for the first year, as the oxalate levels are higher in the first year. After that, the stalks are safe to eat but the leaves can have enough oxalates to make you sick. You would have to eat a lot of rhubarb to actually die from oxalate poisoning.
From http://www.rhubarbinfo.com/poison/
The biodynamic (toxicity) mechanism by which oxalic acid works is somewhat different from organic poisons and is more analogous to heavy metal poisoning. Organic poisons often work through at the biochemical level, e.g. cyanide by interfering with respiration at the cellular level, strychnine by screwing up inter-synaptic transmission. There are many molecular substances in foods which offer no nutritional benefit, and must be processed and excreted. Oxalic acid, for example, is excreted in the urine, and its crystals are commonly found in microscopic urinalysis. Too much oxalic acid in the urine will result in kidney or bladder stones. Calcium combines with oxalic acid to form the less soluble salt, calcium oxalate, which is also found in kidney stones. Plant leaves, especially rhubarb, cabbage, spinach, and beet tops, contain oxalic acid. Oxalic acid is also found in potatoes and peas. Vitamin C is metabolized to oxalic acid; it contributes to over-saturation of the urine with crystals and possibly to stone formation.
The first two images are oxalate crystals. The 3rd is a microscopic image of a rhubarb leaf. The last two are the rhubarb from my garden and the rhubarb pie my wife made, respectively.
For #ScienceSunday curated by Allison Sekuler Rajini Rao Robby Bowles and me.
I leave you with Crystal Blue Persuasion.
Tommy James & the Shondells Crystal Blue Persuasion
Edit Rajini Rao reminded me: happy π approximation day (7/22)
July 22, 2012
very cool! The itals aren’t working though – do you want to fix that before I share on the #ScienceSunday page? We’ll be sending about 10,000 people your way for dessert… 😉
July 22, 2012
So your rhubarb now tastes all right, I assume… thanks for some depth behind the folk saying.
July 22, 2012
That is fascinating!!
July 22, 2012
Extra, extra: We have bacteria (Oxalobacter formigenes) that specifically use oxalate to harness energy in the form of ATP. The oxalate-formate antiporter (OxlT) on these bacterial membranes, bring in oxalate (which has two carboxylic acid groups), breaks it down to release CO2, and transports the remaining formate (one carboxylic acid group) back outside.
As a result of one such transport cycle, a net negative charge is left inside and positive outside. So this transporter behaves as a virtual proton pump. The proton gradient can then be used to make ATP via the ATP synthase. Cool, eh?
July 22, 2012
Old recipes for cooking rhubarb recommend adding a spoonful of white chalk (the one used for writing on blackboards) to the rhubarb. This may well be to form the Calcium oxalate before it reaches the kidneys!
July 22, 2012
Fixed italics Thanks Allison Sekuler
Was delicious William McGarvey
ATP info definitely gave me more energy Rajini Rao
Chalk up a + 1 for Pieter van Pelt
July 22, 2012
Also, skipping harvesting the first year promotes good root development, as doing a restricted on the second year. It is the third where several harvests can be done, about 8 stalks per plant per harvest.
July 23, 2012
Michelle Beissel good advice. Also, we were told to chop off the flower as soon as it pops up. We’ve harvested at least twice this year.
July 23, 2012
Right, Chad Haney. Most important aspect because it has been so hot and dry is to water it enough, they are moisture lovers and a dry spell this season will effect its productivity next season.
Though the huge flower bud is edible and supposedly taste like broccoli, it is also tightly wrapped in small leaves, so unlike some, I don’t eat it, but I do remain curious to how it does taste! Some varieties of rhubarb put out a lot of flowers, I have one that does, it is such a nuisance because the amount of edible stalks are diminished, others are ‘better behaved.’ BTW, I have done a blog post on rhubarb if you ever want to check these points again.
July 23, 2012
Michelle Beissel this summer has been hot and dry. I think that’s why the rhubarb has been small and sad looking. Thanks for the info.
July 25, 2012
I suffered from kidney stone pain until I started eating an orange every day. See my health file at and scroll down to kidney stones.