Earlier quoted context omitted.
iirc vitamin b12 is essentially non-existent in vegan diets. So it's important to either eat meats/seafood, eat a vegan food fortified in it, or take a supplement (the later two are equivalent, just different delivery mechanism)
iirc, that's not quite right. All dietary B12 originates in/on plant sources, you just have to avoid processing that removes it, and include plant sources with good sources. If you try and eat vegan from a typical north american grocery store though, you may have trouble and need to supplement it. On the other hand, selections are pretty good these days, and if you incorporate some nori or legume sprouts (from memory…
Legumes or sprouts are not an adequate source of B12 and neither are other plant sources.
Your assertion that Nori has B12 is downright wrong. B12 is only synthesized by microorganisms.
There are plenty of vegetarian options, but if you are vegan, you have to rely on fortified products and supplements. This has nothing do to with where you happen to live.
You can check recommendations from physicians, researchers and most importantly Vegan associations all across the globe to the see this is true.
“The Vegetarian Resource Group (VRG) suggests that vegans need to have reliable sources of vitamin B12 in their diets. (1) The Vegetarian Nutrition Dietetic Practice Group (VNDPG) of the Academy of Nutrition and Dietetics says that all vegetarians (including vegans) should include a reliable B12 source in their diets, such as fortified foods or supplements. (2) And The Vegan Society goes so far as to state, “What every vegan should know about B12: the only reliable sources of B12 are foods fortified with B12 and supplements.” (3)“
I have seen people get sick ignoring these issues in a vegan diet.
“According to vegan expert and co-author of Vegan for Life, Jack Norris, RD, there are no reliable sources of B12 in plants, contrary to many rumors about sources, such as tempeh, seaweeds, and organic produce. Plants have no B12 requirement, therefore they do not have any active mechanisms to make or store it. When you find B12 in plants, it is due to contamination, which is not a reliable source. Many seaweeds have B12 analogues, through their symbiotic relationship with cobalamin-producing bacteria, however the evidence is not clear that this form is active B12 in humans. And fermented foods, such as tempeh, are not fermented through B12-producing bacteria, thus they are not a source of B12. Rumors about bacteria on the surface of organic produce producing B12 have not been verified. “Chlorella may improve B12 status, but it’s by such a small amount that I wouldn’t rely on chlorella for B12,” adds Norris. Norris stresses that, unless a food obtained from multiple regions consistently improves B12 status, it should not be relied upon as a source of B12.“
A vegan diet can be a healthy and sensible choice for people living in a modern society with access to supplements and fortified foods as well as the care and knowledge to use them. Otherwise it is not an appropriate diet for humans, especially not outside of the modern Western organic supermarket and supplement infrastructure.
https://veganhealth.org/vitamin-b12/vitamin-b12-plant-foods/