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What Is Vitamin B12
B12 is a vitamin produced by bacteria in the soil and water. Prior to modern times, our ancestors consumed enough B12 from vegetation since they didn't have the same hygienic practices of washing it before eating (or chlorinating the water to kill bacteria) like we do now. Animals get their B12 in the same manner—they eat the grass and vegetation that has a bit of soil on it containing B12. However, it's important to note that livestock are typically supplemented B12 because pesticides often kill the bacteria that produce B12 in soil and antibiotic use kills the bacteria in the guts of farm animals.
Why Do We Need It
B12 is essential since all cells in the body need it. The first effects of it are seen in the blood and nervous system. Megaloblastic anemia, characterized by large red blood cells, is a common result of deficiency. A patient even with severe deficiency can tolerate the low red blood cell count which can always be cured by taking small amounts of B12. You only need 4-7 micrograms a day but your chances of getting anemia from being deficient is less than one in a million.
Additionally, it has been observed that B12 can be recycled by the body for up to 20 or even 30 years (assuming you don't consume any more during that time). However, it is very unlikely that you'd be able to completely avoid it for that long. So many foods these days are fortified with it. Though there are recommendations that if you're on a whole food plant-based diet that you should be supplementing it after three years. This is because even an omnivore can be deficient in B12. If you start off deficient when switching to a vegan diet a supplement can immediately correct this deficiency. It's best to get your blood tested first, and then decide whether supplementation is necessary.
Most of the time though the deficiency is related to intestinal diseases and not the diet. But again, the chances are one in a million of developing a disease from being deficient.
Click Here for Part 2 where I talk about the best vegan sources for getting B12.