I would like to endorse that last item, that there is a potential harm that is not widely known. It’s not specific to veganism, but the risk is elevated for them.
Oxalic acid is ubiquitous in plant-based foods. Absorbed oxalic acid can precipitate in the body as calcium oxalate. This most often damages the kidneys, but it can also cause joint pains and degeneration. The crystals are not as inflammatory as the crystals that cause gout, but they are much more persistent.
People who have trouble with fat absorption are at an increased risk for getting too much oxalic acid from their diet, a condition called enteric hyperoxaluria / oxalosis. These include persons treated for obesity with baryatric surgery or old fashioned weight loss drugs, and sufferers of IBD. This is a growing demographic. Their problems with kidneys and joints can very easily be imputed to pre-existing conditions like diabetes, overweight or autoimmune disorders.
The studies on oxalate content of foods are somewhat conflicting as to the precise amounts in each plant or foodstuff. It is not always clear what part is bound to e.g. calcium and how much is in a more readily absorbed form.
Legumes seem to contain significant amounts. Rhubarb is a well known source, but how many people know that a larger serving of carrots, sweet potatoes or almonds can be just as dangerous? Processing methods have a big effect: instant coffee has manyfold higher levels than ground and percolated coffee.
Oxalic acid also has some endogenous sources in the body, such as protein metabolism. It is a metabolite of both xylitol and ascorbic acid. Gut flora can both generate and consume oxalic acid, depending on the species.
I haven’t found any oxalate data on novel highly processed plant based foods like meat and dairy substitutes. Fermentation might push it either way. Many of the ingredients, like mushrooms, almonds, spinach, beetroot and coconut seem to have very high levels of oxalate to begin with.
Perhaps you can now see why I’m worried. Add some supplement (or eating liver as suggested in other comments) that has too much vitamin A or D to the mix and you might also get a high blood calcium level and more crystallization in the body.
Oxalic acid is more famously the most common constituent of stones in the urinary tract. Kidney stones are often described as a “ten” on the pain scale from 1 to 10. It is not given that large stones will be the first symptom of too much oxalic acid, their formation might require low hydration or abnormalities in the pH of the urine. Smaller stones or crystals might imitate a urinary tract infection or a STD with painful discharge. There might be no urinary symptoms other than those resulting from kidney damage. Animal protein intake is a risk factor for renal and urinary tract calculi, so if vegans don’t have a higher risk of stones it does not necessarily mean they are safe from other oxalate pathologies. But stones are definitely something to look for.
The standard way to prevent problems with dietary oxalic acid is to consume a small amount of calcium carbonate after meals to bind it in a non-soluble form. I would also recommend that people avoid xylitol and big doses of vitamins A, C and D.
If you are now concerned about it (you’re welcome!), oxalate absorption and production can be assessed with a 24-hour urine collection sample. Note that the upper reference range might not be all that far from what is observed in primary (i.e. hereditary) hyperoxaluria, a very serious condition.
Most likely oxalic acid does not and will not have a big impact on the health of the vegan population. But is has some potential of being a major under-the-radar (persistent and low-grade inflammatory, crystal deposits perhaps hard to image) threat for serious and long-term problems like chronic kidney disease and osteoarthritis. Why do some people get these conditions early in life?
I hope this helps.
PS. I’m not a vegan, but I believe meat and dairy has had an immense negative impact on everyone’s health, including vegans. There is of course the historic zoonotic origin of many high impact infectious diseases in domesticated animals. But I’m talking about a more modern development.
It used to be the case that the distribution and prevalence of gut microbiota was largely dependent on the fitness and mobility of the host. Nowadays the vast majority of mammal biomass is either livestock or humans. Their mobility and that of their manure is mainly supported by technology.
This independence of the host’s fitness frees the microbiome to increase its own fitness in new, potentially pathogenic ways. One obvious modification could be to make the host eat more. Because the manure is spread by mechanized means, any increase in eaten and excreted volume results in a roughly proportionate advantage to the microbe. Animal breeding and market forces aren’t strictly working against this development, perhaps the opposite.
This model of the etiology of obesity fits with the geographical prevalence: lower at high altitudes, i.e. upstream of agriculture. It would also explain why wild animals are getting fatter, if that is the case. It suggests the quick health fix of getting a fecal transplant from a healthy hunter-gatherer. The more remote and isolated the donor, the better. But we would have to be careful not to corrupt them as they get wealthy off their product.
I would like to endorse that last item, that there is a potential harm that is not widely known. It’s not specific to veganism, but the risk is elevated for them.
Oxalic acid is ubiquitous in plant-based foods. Absorbed oxalic acid can precipitate in the body as calcium oxalate. This most often damages the kidneys, but it can also cause joint pains and degeneration. The crystals are not as inflammatory as the crystals that cause gout, but they are much more persistent.
People who have trouble with fat absorption are at an increased risk for getting too much oxalic acid from their diet, a condition called enteric hyperoxaluria / oxalosis. These include persons treated for obesity with baryatric surgery or old fashioned weight loss drugs, and sufferers of IBD. This is a growing demographic. Their problems with kidneys and joints can very easily be imputed to pre-existing conditions like diabetes, overweight or autoimmune disorders.
The studies on oxalate content of foods are somewhat conflicting as to the precise amounts in each plant or foodstuff. It is not always clear what part is bound to e.g. calcium and how much is in a more readily absorbed form.
Legumes seem to contain significant amounts. Rhubarb is a well known source, but how many people know that a larger serving of carrots, sweet potatoes or almonds can be just as dangerous? Processing methods have a big effect: instant coffee has manyfold higher levels than ground and percolated coffee.
Oxalic acid also has some endogenous sources in the body, such as protein metabolism. It is a metabolite of both xylitol and ascorbic acid. Gut flora can both generate and consume oxalic acid, depending on the species.
I haven’t found any oxalate data on novel highly processed plant based foods like meat and dairy substitutes. Fermentation might push it either way. Many of the ingredients, like mushrooms, almonds, spinach, beetroot and coconut seem to have very high levels of oxalate to begin with.
Perhaps you can now see why I’m worried. Add some supplement (or eating liver as suggested in other comments) that has too much vitamin A or D to the mix and you might also get a high blood calcium level and more crystallization in the body.
Oxalic acid is more famously the most common constituent of stones in the urinary tract. Kidney stones are often described as a “ten” on the pain scale from 1 to 10. It is not given that large stones will be the first symptom of too much oxalic acid, their formation might require low hydration or abnormalities in the pH of the urine. Smaller stones or crystals might imitate a urinary tract infection or a STD with painful discharge. There might be no urinary symptoms other than those resulting from kidney damage. Animal protein intake is a risk factor for renal and urinary tract calculi, so if vegans don’t have a higher risk of stones it does not necessarily mean they are safe from other oxalate pathologies. But stones are definitely something to look for.
The standard way to prevent problems with dietary oxalic acid is to consume a small amount of calcium carbonate after meals to bind it in a non-soluble form. I would also recommend that people avoid xylitol and big doses of vitamins A, C and D.
If you are now concerned about it (you’re welcome!), oxalate absorption and production can be assessed with a 24-hour urine collection sample. Note that the upper reference range might not be all that far from what is observed in primary (i.e. hereditary) hyperoxaluria, a very serious condition.
Most likely oxalic acid does not and will not have a big impact on the health of the vegan population. But is has some potential of being a major under-the-radar (persistent and low-grade inflammatory, crystal deposits perhaps hard to image) threat for serious and long-term problems like chronic kidney disease and osteoarthritis. Why do some people get these conditions early in life?
I hope this helps.
PS. I’m not a vegan, but I believe meat and dairy has had an immense negative impact on everyone’s health, including vegans. There is of course the historic zoonotic origin of many high impact infectious diseases in domesticated animals. But I’m talking about a more modern development.
It used to be the case that the distribution and prevalence of gut microbiota was largely dependent on the fitness and mobility of the host. Nowadays the vast majority of mammal biomass is either livestock or humans. Their mobility and that of their manure is mainly supported by technology.
This independence of the host’s fitness frees the microbiome to increase its own fitness in new, potentially pathogenic ways. One obvious modification could be to make the host eat more. Because the manure is spread by mechanized means, any increase in eaten and excreted volume results in a roughly proportionate advantage to the microbe. Animal breeding and market forces aren’t strictly working against this development, perhaps the opposite.
This model of the etiology of obesity fits with the geographical prevalence: lower at high altitudes, i.e. upstream of agriculture. It would also explain why wild animals are getting fatter, if that is the case. It suggests the quick health fix of getting a fecal transplant from a healthy hunter-gatherer. The more remote and isolated the donor, the better. But we would have to be careful not to corrupt them as they get wealthy off their product.