Not getting enough B can lead to devastating results. Cases reported of paralysis, blindness, even death.
Where do we get vitamin B12? Not necessarily from meat, as you might expect. Instead, we get B12 from microbes in the earth. We used to get them in the water we drink. Today we sanitize our water supply which kills off any living microbes.
Anyone eating a plant-based diet needs to supplement with a good reliable source of B12. If you are under 65, the easiest way to get B12 is to take at least one 2,000 mcg supplement each week or a daily dose of 50mcg. The preferred supplement for B12 is cyanocobalamin. Other forms have not been proven to be effective. ( like methylcobalamin)
After 65, though, our ability to absorb B12 declines. In which case, Plant-Based adults over 65 need to increase their B12 intake to 1,000 mcg daily.
Some foods are fortified with vitamin B12. However, we would need to eat at least four servings a day of each, making sure it is eaten four to six hours apart. New labeling mandates from January 1, 2020, we need 4.5 mcg three times a day. For B12-fortified nutritional yeast, two teaspoons three times a day would be enough. Taking a supplement is cheaper and more convenient. As Dr. McGregor likes to say, " Our fellow great apes get all the B12 they need eating bugs, dirt, and feces, but I'd suggest supplements instead!"