Vitamin B12, or cobalamin, is not produced by plants. Sources of B12 include fish, shellfish, meat, eggs, and dairy products. Therefore, for vegans, it is necessary to supplement their diet with B12.
What Does Vitamin B12 Do?
Vitamin B12 is important in the function of the brain and nervous system, as well as in the formation of red blood cells. It also plays a role in producing DNA and RNA, and in the health of nerve cells. Intrinsic factor, produced by the parietal cells in the stomach, is needed to absorb B12 (cobalamin) on location in the small intestine. If there is an issue with intrinsic factor, such as in the case of pernicious anemia, then B12 cannot be absorbed and megaloblastic anemia occurs, resulting in red blood cells that are deficient because they are unable to divide, and an insufficient number of circulating red blood cells.
Required for metabolism in each of the cells in the body, Vitamin B12 is stored mainly in the liver, with some stored in the muscles. However, if you never replenish your B12 stores, you will run out of B12 and run into health problems. B12 deficiency symptoms include weakness, fatigue, paranoia and hallucinations, jaundice, numbness or tingling of the extremities, balance issues, problems with cognition and memory loss. There are blood detection tests to determine whether someone is deficient in B12 levels.
What Can a Vegan Do?
The daily recommended dietary allowance of B12 for an adult is 2.4 micrograms, according to the National Institutes of Health. You can get B12 as a dietary supplement in the form of cyanocobalamin, which the body changes to methylcobalamin and 5-deoxyadenosylcobalamin, the active forms of vitamin B12. You can also get the already active form, methylcobalamin, as a supplement. If you don’t have a health problem with intrinsic factor, then you should be able to absorb approximately 10 micrograms of a 500 microgram oral supplement of B12. As you can see, very little of your B12 supplement is actually absorbed, even if you are healthy. In addition to oral supplements, sublingual B12 supplements are also available. I have taken the sublingual B12, and they are fun in that they melt under your tongue.
Some nutritional yeast products contain B12, and some foods like breakfast cereals are fortified with B12, so these are extra ways in which you can boost your daily dose of B12.
Synthetic Vitamin B12 Requires One Less Step for Absorption
The vitamin B12 that is naturally available in foods such as fish and meat are bound to the protein, and can be released only upon exposure to hydrochloric acid in the stomach and in the presence of the enzyme, gastric protease. The synthetic vitamin B12 available in dietary supplements and fortified foods does not need to be cleaved and released as such, and can already be used in the body. Once B12 is free, it joins with intrinsic factor, and then together, the complex is absorbed in the distal ileum of the small intestine.
Bottom Line: For Vegans, Vitamin B12 Must Be Supplemented in the Diet