Vitamin B12 is a unique vitamin for many reasons. It was the most recent vitamin to be discovered when scientists finally isolated its pure form in 1948. Until that time, doctors knew only that an “extrinsic factor” existed (a compound that had to be ingested) and was necessary to prevent pernicious anemia.
This deficiency disease was reported as early as the 1820s but it wasn’t until the 1920’s that an extract from the liver was found to be the cure, and still more years passed before the “extrinsic factor” was finally identified as vitamin B12.
The digestion and absorption of vitamin B12 is more complicated than other vitamins: Three components are necessary for a human to be able to absorb adequate amounts. If one of these is missing, injections become the only way to prevent a deficiency.
First, the stomach must be present. This may sound obvious at first, but in fact, many nutrients are actually absorbed in the small intestine and a stomach is not necessary for human survival.
In the case of vitamin B12, however, “intrinsic factor” must be present in the stomach to combine with the “extrinsic factor” (vitamin B12) for absorption to occur. The stomach produces this intrinsic factor.
A person may have to have their stomach removed due to severe ulcers, polyps, or cancer, and afterward will not be able to absorb oral B12. In this case, they would need injections of the vitamin because no matter how much they eat, it will not be absorbed.
The second component is stomach acid. Even if the stomach is present, a condition of low acid production (achlorhydria) is not uncommon in the elderly. This acid environment is necessary for the intrinsic and extrinsic factors to combine.
Another cause of low stomach acid is when antacid medications are taken consistently over long periods of time. If stomach acid is lacking and a person becomes B12 deficient, monthly injections are needed to prevent pernicious anemia.
The third component necessary is the functioning area of the small intestine where the vitamin is actually absorbed. Known as the terminal ileum, it is the last part of the small intestine just before the GI tract leads into the large intestine.
Some people may need to have this part of their ileum removed due to inflammation from Crohn’s disease, or other chronic bowel irritations. Even if the ileum is present, if it is inflamed or scarred from irritable bowel disease, the vitamin will not be absorbed adequately. For these people, vitamin B12 injections are a lifesaver.
Who else needs vitamin B12 injections? Not healthy people who eat balanced diets. Not people who feel tired all the time and lack energy but have not been diagnosed with a deficiency of the vitamin.
Not even strict vegetarians who don’t get a source of the vitamin in their diet. Even though B12 is only found in animal products, there are other ways to consume it orally: Some can be found in certain nutritional yeasts; many bowls of cereal are fortified with B vitamins including B12, and other foods such as energy bars are also fortified in many instances.
The back-up plan for strict vegans (who consume no animal products) is taking a daily vitamin B12 pill from the bottle-no injection is needed because there is no problem absorbing the vitamin!
Injections are only necessary for people who are missing their stomach, their stomach acid, or their terminal ileum. Taking injections when your body is perfectly capable of absorbing the vitamin orally will not serve any purpose, change any symptoms, or resolve any feelings of low energy.
This myth comes from the fact that a person who is truly B12 deficient has a deadly form of anemia and can be cured by the shots. The only thing a B12 injection can cure is a B12 deficiency.
To check for possible deficiency disease, a simple lab test (the MCV or mean corpuscular volume) indicates that red blood cells are not dividing and multiplying at the appropriate rate. Known as megaloblastic anemia, these large cells could indicate potential pernicious anemia.
If further diagnostics are needed there are specific absorption tests available. It certainly makes sense to have your doctor diagnose the problem and identify the source before starting any injection treatments.
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