From solid vegan nutritionist Ginny Messina in an article on vitamin/mineral supplements:But vegan diets always need to be supplemented with B12 on a regular basis (not “occasionally”) and often with vitamin D. If you don’t use iodized salt you should take a supplement of iodine. I recommend a DHA supplement as well, although the research on benefits remain conflicting.
My two cents: From what I've read, the population at large is mostly B-12 deficient which is problematic since B-12 is so critical to long-term health. No one should be adding extra iodized (regular table) salt to their food because of the negative effects of salt (hypertension, etc.). (Even sea salt should be limited.) Iodine is critical for thyroid health, but getting iodine from sea sources (kelp, dulse flakes, etc.) is far healthier than from iodized table salt. (The government mandated the addition of iodine to table salt years ago to make sure the population got iodine, a non-optional ingredient. Table salt is nothing but a delivery vehicle for the iodine which we do need. Gov: "What does every American crave to which we can iodine?" Answer: "Table salt.")
Lots of vegans STILL don't take B-12 regularly, to their detriment. Omnivores get B-12 from meat, vegans and vegetarians have to get it from other sources. Supplements are the safest, most predictable way. It's inexpensive and plentiful. (The methylcobalamin version of B-12 is supposedly better absorbed than cyanocobalamin -- look on the label for the kind. But either is better than none.)
n.b.—the presence of B-12 in meat is not an argument AGAINST plant-based diets. Animals get the bacteria that synthesizes to B-12 by eating plants in nature, and they process it well because of their extensive gut systems, getting into their flesh which humans consume. We would get the same bacteria from nature if we "grazed" plants like we were created to do (Genesis 1:29). Instead, we eat sterilized plant foods, miss the bacteria, and thus produce little B-12 of our own. (I've made this argument in this space many times before and make it again only to dispel the common myth that the presence of B-12 in meat is an argument against plant-based diets.)
(Thanks to vegan.com for the link.)