Oxalic acid: sorting through threads/data for fact, fiction, and feelings

I recently left my redfoot on his own for two weeks while I was away on vacation. His enclosure maintains great temp and humidity levels thanks to timers and thermostats; he had adequate food and water, and seems fine, although he enjoyed a soak and a big feast when I got back.

Most of the food I left him with was pothos and opuntia, more of the former than the latter, as his enclosure was heavily planted with pothos in addition to the cut leaves I left him. These foods work well when I'm away as they don't spoil quickly.

Oxalic acid is sort of a concern of mine... sort of because of the vastly differing opinions on the danger it poses to tortoises.

I've read pretty widely, both here on TFO and out on the rest of the internet, trying to sort the wheat from the chaff... I'm unable.

Darwin, my redfoot, seems to really enjoy eating pothos, which is why I plant his enclosure with it, but I don't want to kill him with kindness.

When I'm not on vacation, he doesn't eat much pothos, mostly a few nibbles on the plantings in his enclosure, but it's a nice mold-free and non-wilting staple for when I travel, so I'd like to keep it on the table (so to speak) if it's a safe option.

With that in mind, I have the following questions for the TFO braintrust:

1) is oxalic acid bad for my redfoot?
1a) how much is ok for torts to consume?
1b) can the potential negative effects be ameliorated with hydration or other foods?

Please don't tell me to use the search function... I have, and the results are inconclusive, mixed with hearsay ("it's bad for cats so it must be bad for tortoises").

Thanks,

Jamie

My previous comments on this topic posted here on TFO are based on scientific research, that's the facts, no sorting required.

Kapidolo Farms said:

My previous comments on this topic posted here on TFO are based on scientific research, that's the facts, no sorting required.

Click to expand...

Thanks, but yours is one voice among many, and your posts are hard to find (at least for me)... If you have a link to the blog you mentioned on FB, or key posts here, I'd love to read them.

J

Kapidolo Farms said:

My previous comments on this topic posted here on TFO are based on scientific research, that's the facts, no sorting required.

Click to expand...

What conclusions have been reached?

Is it okay to feed them oxalis for example? More spinach in the diet?

There are three issues here.
-One is calcium oxalate crystals - raphides - which are listed as "toxic", causing irritation and swelling of the tongue, esophagus, etc.
-The second is the pressence of oxalates that then binds with calcium and limits calcium availability.
-The third is too much oxalic acid can bind with calcium in the urinary system and leads to stones or uroliths.

I agree - most all we hear is based on heresay and information taken from studies/issues with other animals and is not based on studies or facts about the way chelonians process foods.

raphides are indeed of concern with mammals. Plants have evolved this mechanism as a way it seems to make themselves unpalatable and not get eaten. For mammals, this does indeed result in swelling and irritation and worse. However, there is absolutely no cases of any chelonian ever being affected by raphides. Just as they can devour a prickly pear pad loaded with glocids or a thistle that I cannot handle without gloves, raphides also are of no effect.

Oxalates do indeed bind with calcium. However, the issues should be how much free calcium is still available even with some bound by the creation of calcium oxalate? As William @Kapidolo Farms has pointed out in several posts and his talk at TTPG - many of the "forbidden plants" have good levels of calcium even after considering the binding of some with the oxalates. It seems the overall ratios in the diet just as with phosphates, is the key concern here.

That then leads to the warning of urolith formation or stones. Again in mammals, that is a concern and can be a cause of kidney stones with the formation of calcium oxalate uroliths. However, the assumption that the same happens in chelonians is not borne out by actual science. If fact in a very compreshensive study of any urolith and veterinarian would send them, it was found that absoluted none of the uroliths found in chelonians creating a "stone problem" contained any concreation of any form of calcium. It is purine based stones that can cause problems with chelonians and has nothing to do with calcium or therefore oxalates binding with calcium. So it is the processing of excess proteins in the diet, not calcium binding, that creates all know cases of stone issues that have indeed been tested and verified.

Markw84 said:

There are three issues here.
-One is calcium oxalate crystals - raphides - which are listed as "toxic", causing irritation and swelling of the tongue, esophagus, etc.
-The second is the pressence of oxalates that then binds with calcium and limits calcium availability.
-The third is too much oxalic acid can bind with calcium in the urinary system and leads to stones or uroliths.

I agree - most all we hear is based on heresay and information taken from studies/issues with other animals and is not based on studies or facts about the way chelonians process foods.

raphides are indeed of concern with mammals. Plants have evolved this mechanism as a way it seems to make themselves unpalatable and not get eaten. For mammals, this does indeed result in swelling and irritation and worse. However, there is absolutely no cases of any chelonian ever being affected by raphides. Just as they can devour a prickly pear pad loaded with glocids or a thistle that I cannot handle without gloves, raphides also are of no effect.

Oxalates do indeed bind with calcium. However, the issues should be how much free calcium is still available even with some bound by the creation of calcium oxalate? As William @Kapidolo Farms has pointed out in several posts and his talk at TTPG - many of the "forbidden plants" have good levels of calcium even after considering the binding of some with the oxalates. It seems the overall ratios in the diet just as with phosphates, is the key concern here.

That then leads to the warning of urolith formation or stones. Again in mammals, that is a concern and can be a cause of kidney stones with the formation of calcium oxalate uroliths. However, the assumption that the same happens in chelonians is not borne out by actual science. If fact in a very compreshensive study of any urolith and veterinarian would send them, it was found that absoluted none of the uroliths found in chelonians creating a "stone problem" contained any concreation of any form of calcium. It is purine based stones that can cause problems with chelonians and has nothing to do with calcium or therefore oxalates binding with calcium. So it is the processing of excess proteins in the diet, not calcium binding, that creates all know cases of stone issues that have indeed been tested and verified.

Click to expand...

Thanks so much for this thoughtful and detailed response.

Jamie

Markw84 said:

There are three issues here.
-One is calcium oxalate crystals - raphides - which are listed as "toxic", causing irritation and swelling of the tongue, esophagus, etc.
-The second is the pressence of oxalates that then binds with calcium and limits calcium availability.
-The third is too much oxalic acid can bind with calcium in the urinary system and leads to stones or uroliths.

I agree - most all we hear is based on heresay and information taken from studies/issues with other animals and is not based on studies or facts about the way chelonians process foods.

raphides are indeed of concern with mammals. Plants have evolved this mechanism as a way it seems to make themselves unpalatable and not get eaten. For mammals, this does indeed result in swelling and irritation and worse. However, there is absolutely no cases of any chelonian ever being affected by raphides. Just as they can devour a prickly pear pad loaded with glocids or a thistle that I cannot handle without gloves, raphides also are of no effect.

Oxalates do indeed bind with calcium. However, the issues should be how much free calcium is still available even with some bound by the creation of calcium oxalate? As William @Kapidolo Farms has pointed out in several posts and his talk at TTPG - many of the "forbidden plants" have good levels of calcium even after considering the binding of some with the oxalates. It seems the overall ratios in the diet just as with phosphates, is the key concern here.

That then leads to the warning of urolith formation or stones. Again in mammals, that is a concern and can be a cause of kidney stones with the formation of calcium oxalate uroliths. However, the assumption that the same happens in chelonians is not borne out by actual science. If fact in a very compreshensive study of any urolith and veterinarian would send them, it was found that absoluted none of the uroliths found in chelonians creating a "stone problem" contained any concreation of any form of calcium. It is purine based stones that can cause problems with chelonians and has nothing to do with calcium or therefore oxalates binding with calcium. So it is the processing of excess proteins in the diet, not calcium binding, that creates all know cases of stone issues that have indeed been tested and verified.

Click to expand...

This presents a lot of good info, but what's the bottom line? Can we feed stuff with high oxalate content, like oxalis for example, to our tortoises? Or best to stick to things that we know are safer?

Tom said:

This presents a lot of good info, but what's the bottom line? Can we feed stuff with high oxalate content, like oxalis for example, to our tortoises? Or best to stick to things that we know are safer?

Click to expand...

What this means for me - is that I don't worry about oxalates. I don't go out of my way to avoid them but I don't choose foods with high levels just as I don't choose foods with high phosphorus levels. I stay focused on the overall free calcium level in the total diet. I ignore raphide warnings and look at nutritional value. I am not concerned about them nibbling on an enclosure plant with high raphides, but do not mix that plant into my servings for their food for the day. I would not pick oxalis and add it to their food, but am not concerned if they eat some. I do feed some spinach now. It has such good vitamin and calcium levels it is a good food. It is a great example of the misapplied oxalic acid causing stones and raphide warnings. As always moderation and total balance.

Markw84 said:

What this means for me - is that I don't worry about oxalates. I don't go out of my way to avoid them but I don't choose foods with high levels just as I don't choose foods with high phosphorus levels. I stay focused on the overall free calcium level in the total diet. I ignore raphide warnings and look at nutritional value. I am not concerned about them nibbling on an enclosure plant with high raphides, but do not mix that plant into my servings for their food for the day. I would not pick oxalis and add it to their food, but am not concerned if they eat some. I do feed some spinach now. It has such good vitamin and calcium levels it is a good food. It is a great example of the misapplied oxalic acid causing stones and raphide warnings. As always moderation and total balance.

Click to expand...

Great!

Thanks,

Jamie

Thanks Mark. I guess it must be my writing skills. I feel I have beaten this to death.

Markw84 said:

There are three issues here.
-One is calcium oxalate crystals - raphides - which are listed as "toxic", causing irritation and swelling of the tongue, esophagus, etc.
-The second is the pressence of oxalates that then binds with calcium and limits calcium availability.
-The third is too much oxalic acid can bind with calcium in the urinary system and leads to stones or uroliths.

I agree - most all we hear is based on heresay and information taken from studies/issues with other animals and is not based on studies or facts about the way chelonians process foods.

raphides are indeed of concern with mammals. Plants have evolved this mechanism as a way it seems to make themselves unpalatable and not get eaten. For mammals, this does indeed result in swelling and irritation and worse. However, there is absolutely no cases of any chelonian ever being affected by raphides. Just as they can devour a prickly pear pad loaded with glocids or a thistle that I cannot handle without gloves, raphides also are of no effect.

Oxalates do indeed bind with calcium. However, the issues should be how much free calcium is still available even with some bound by the creation of calcium oxalate? As William @Kapidolo Farms has pointed out in several posts and his talk at TTPG - many of the "forbidden plants" have good levels of calcium even after considering the binding of some with the oxalates. It seems the overall ratios in the diet just as with phosphates, is the key concern here.

That then leads to the warning of urolith formation or stones. Again in mammals, that is a concern and can be a cause of kidney stones with the formation of calcium oxalate uroliths. However, the assumption that the same happens in chelonians is not borne out by actual science. If fact in a very compreshensive study of any urolith and veterinarian would send them, it was found that absoluted none of the uroliths found in chelonians creating a "stone problem" contained any concreation of any form of calcium. It is purine based stones that can cause problems with chelonians and has nothing to do with calcium or therefore oxalates binding with calcium. So it is the processing of excess proteins in the diet, not calcium binding, that creates all know cases of stone issues that have indeed been tested and verified.

Click to expand...

It means that as long as the free calcium is greater than the phosphorus, it's "safe".

Tom said:

This presents a lot of good info, but what's the bottom line? Can we feed stuff with high oxalate content, like oxalis for example, to our tortoises? Or best to stick to things that we know are safer?

Click to expand...

jsheffield said:

Thanks, but yours is one voice among many, and your posts are hard to find (at least for me)... If you have a link to the blog you mentioned on FB, or key posts here, I'd love to read them.

J

Click to expand...

FWIW, when I write about controversial things, it's not my 'voice' it's my bringing to others scientific voice to the lay reader. I back up my POV with vetted scientific research.

https://kapidolofarms.com/wp-content/uploads/2018/11/With-notes-KapidoloFarmsTTPG.pdf .

I must confess I get an ever so slight thrill in tripping up veterinarians with science they have ignored, as they perpetuate the bull$hit.

Kapidolo Farms said:

It means that as long as the free calcium is greater than the phosphorus, it's "safe".

Click to expand...

I can tell you right now that I'm not going to look up the "free calcium" or the phosphorous levels of every plant I can get my hands on. I don't know too many other people that are going to do that either, so how about a list of the foods that were once cautioned against, but now, due to your research on the topic, we think are okay to feed? Like the aforementioned spinach, for example. What foods have "we" been saying not to feed, that are now okay to feed?

A bit of contradictory science in a FB discussion on the same topic was offered up by someone this afternoon....

Jamie

Awesome work gentlemen! To a non-science person the research was daunting.

Maybe, if you are talking about Karen R. post you could bring that actual info into the discussion here. I did not find any 'contradictions'. I imagine you can cut and paste?

jsheffield said:

A bit of contradictory science in a FB discussion on the same topic was offered up by someone this afternoon....

Jamie

Click to expand...

Very few analysis of the free calcium seems to be published. I'll not again again again again again again post the opuntia data.
The diets of Cal desert tortoises have been published, and much of their diet is high in oxalates. But they also chew on bone and eat egg shells when found. So maybe the 'trick' is to offer calcium to create the 'more calcium' free calcium in the total diet, and walk away from the each and every food quest.

I get it, we would both help fund further study on many of these questions. What I do is search the lit for what I can.

Tom said:

I can tell you right now that I'm not going to look up the "free calcium" or the phosphorous levels of every plant I can get my hands on. I don't know too many other people that are going to do that either, so how about a list of the foods that were once cautioned against, but now, due to your research on the topic, we think are okay to feed? Like the aforementioned spinach, for example. What foods have "we" been saying not to feed, that are now okay to feed?

Click to expand...

Kapidolo Farms said:

Maybe, if you are talking about Karen R. post you could bring that actual info into the discussion here. I did not find any 'contradictions'. I imagine you can cut and paste?

Click to expand...

https://cdn.ymaws.com/members.arav.org/resource/resmgr/Files/Proceedings_2007/2007_35.pdf

Quote

Nephrocalcinosis
Nephrocalcinosis is due to the deposit of calcium salts (mineral) into the soft tissues and is a common findings in reptiles.39,SS,116 This deposition may be identified within the glomerular mesangium or basement membranes in both the glomeruli as well as the renal tubules. Calcium deposits may be recognized within the interstitium as well as involving the vascular structures. There are two general mechanisms oftissue mineralization: dystropic and metastatic. Dystrophic calcification occurs in nonviable or dying tissues. Dystrophic is not associated with hypercalcemia or other disturbances of calcium homeostasis. It occurs in cells injured in a variety of ways, including vascular, toxic, metabolic, or inflammatory diseases. Metastatic calcification results in the deposition of calcium in vital tissues and reflects some disturbance in calcium metabolism. In renal disease, it is difficult to differentiate dystrophic (degenerative lesions of uremia) from metastatic calcification (secondary hyperparathyroidism). Histologically calcification is characterized by irregular foci of dense basophilic [blue] material that can be identified by special stains. Additional sites ofmineral deposition include the great vessels, heart, lung, intestines and skin.90,97
Renal mineralization is rarely described in amphibians. Extensive mineralization of the kidneys and heart was noted in an Argentine horned frog (Ceratophrys ornata).2S This frog also had coelomic cavity fluid accumulation. The kidneys were enlarged and mottled with yellow-gray foci.
Edible frog tadpoles (Rana esculenta), Solomon Island leaf frogs (Ceratobatrachus guentheri), and leopard frog tadpoles (Rana pipiens) that are fed diets high in oxalates develop an oxalic calculogenesis.18,29,99 These may represent dietary imbalances secondary to diets high in oxalates (e.g., spinach). There will be extensive mineralization as well as granulomas forming around crystals consistent with oxalic crystals within the renal tubules. They have been reported as a common incidental finding and occasionally leading to nephrosis.

Quote

Page 90 has references to oxalates that was pointed out by Karen ... they don't seem definitive (especially given that the study is dealing with amphibians, not turtles), but interesting nonetheless, and possibly worthy of further study and discussion for those curious enough.

Jamie

Thanks, when I'm on my phone, I dread cut and paste, I won't try.

They are talking about frogs. I don't think it correlates well. One of the three references that those authors used was for captive animals at the woodland park zoo, so at least, I'm hopeful there will be diet into.

jsheffield said:

I am able to cut and paste...

https://cdn.ymaws.com/members.arav.org/resource/resmgr/Files/Proceedings_2007/2007_35.pdf

Page 90 has references to oxalates that was pointed out by Karen ... they don't seem definitive, but interesting nonetheless, and possibly worthy of further study and discussion.

Jamie

Click to expand...

I think I'll not worry about oxalic acid in Darwin's food, but will continue to feed for diversity and balance on the assumption that a varied diet, in combination with access to water/spankings, along with optimized temp & humidity, will support his health and growth and longevity.

I'll probably put kale and spinach back into the diet as minor components, and also continue to is pothos as a planting in his enclosure.

Thanks so much to all the contributors and contributions to th this discussion.

Jamie