Vegans will often say that having an animal-free diet is best for our health and is actually the diet that humans should be eating to function optimally. To which meat eaters will raise the issue of B12, and how (they believe) it is only to be found in animal products [thus vouching for an evolutionary need to eat meat and eggs). These days, with all our water being treated to remove pathogens, it is obviously best to take b12 supplements, but the question remains: do vegans have a point? Is there actually enough b12 in water for humans to not develop an insufficiency?

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    $\begingroup$ I was not aware that drinking water was a source of B12 at all! It might be clearer to start with that information, and then ask whether the source is sufficient. $\endgroup$
    – gilleain
    Commented Nov 14, 2017 at 13:44
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    $\begingroup$ Even if it was the case that B-12 could be absorbed from water-borne microorganisms, 1) Wouldn't it depend on the particular body of water you drink from, e.g. a stagnant pond vs a spring-fed mountain stream? 2) Before water treatment, weren't water-born microorganisms a major source of diseases such as cholera? $\endgroup$
    – jamesqf
    Commented Nov 14, 2017 at 18:10
  • $\begingroup$ @jamesqf It would certainly depend on the source I think. Obviously, stagnant water with more algae, particularly in lakes would contain more B12 than a mountain spring. I was concerned about cholera, but cholera and many other such diseases are the results of non-nomadic living. City environments, where waste is allowed to build up, cause widespread epidemics. My question is in terms of human history, before the advent of agriculture and settler communities. $\endgroup$ Commented Nov 14, 2017 at 18:47

2 Answers 2


Of course there is no evidence for the superiority of the vegan diet claim to begin with, so there is that, and there are plenty of vegan foods fortified with B12, even some from non-animal sources.

No, there is not enough B12 in treated water nor well water for a human. There can be enough B12 in untreated river/lake water because it contains high levels of fecal matter or algae which is high in B12 (b12 is manufactured by anaerobes). Of course these are the things you want removed from your drinking water so reducing B12 is inevitable. Also can contain enough being the key phrase it depends on the water source, cleaner river contain less.

Evolutionarily speaking humans eat animals for the same reason every omnivore and many herbivores (deer, ect) do, because we can, it is generally a superior nutritional substrate which is more than enough for evolution to favor it.

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  • $\begingroup$ Could you elaborate on your definition of 'superior'? I said vegan diets were healthier not 'superior'. @John $\endgroup$ Commented Nov 14, 2017 at 17:46
  • $\begingroup$ which there is no evidence for. And by superior substrate I mean easier to digest, more calories, more vitamins, an animals contains everything you need since it is basically made of the same stuff. $\endgroup$
    – John
    Commented Nov 15, 2017 at 0:33
  • $\begingroup$ No evidence? youtube.com/watch?v=30gEiweaAVQ $\endgroup$
    – Samuel
    Commented Dec 18, 2017 at 18:07
  • $\begingroup$ @Samuel Vegetarian not the same as vegan diet, it is a pretty important distinction. $\endgroup$
    – John
    Commented Dec 18, 2017 at 21:27
  • $\begingroup$ The video compares research from 3 primary groups, meat eaters, vegetarians, and vegans, on most points. $\endgroup$
    – Samuel
    Commented Dec 19, 2017 at 1:41

Fermented food is a safer and higher b12 option for a vegan, it can have a lot higher content of yeasts and bacteria than safe water, and it can be controlled.

Most vegan foods (not protein rich) can safely ferment until 50% to 99%(sry for the humor) of their expiration date, living plant matter in any carb/plant mix will generally kick off a good fermentation. some foods like salad couscous are full of yeast and become unappetizing and gluey with yeast a long time before they become unhealthy to eat.

It would be difficult to design a pond/lake which has high content of bacteria and archea and chlorella to be optimal for humans, whilst also being safe for children. Rivers should have mats of algea that filter the water, however they are so variable, it's pot luck if a river has an excess of nitrogen or a silty bacterial nuisance, A river can be jam packed with nitrogen detritus, and after a storm/ in the wrong place it's not reliable.

In winter the lake can become less productive biologically, too high in nitrogen, and if it's biologically rich it will be subject to wild seasonal variability.

Blooms of animals, daphnia, cyclops can occur, eating whatever is making the vitamin b12, and any unseen bacteria can bloom, which benefit from warmth and that will thrive noxiously in the gut.

A snail doesn't even have a lot more neurons than a tardigrade, and definitely a lot less neurons than small insects and acarians that you accidentally consume from plants.

You can reprimand me for the lack of references, it will give be a subject of study, however it's too broad a topic to reference and research right now, unless you think i've made an overstatement.


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