Specific cells in the stomach lining, called parietal cells, secrete two substances that are important to B12 absorption. One is stomach acid – it splits food and B12 apart, allowing the vitamin to bind to the saliva’s R-protein. The other substance, called intrinsic factor, mixes with the stomach’s contents and travels with them into the first part of the small intestine – the duodenum. Once in the duodenum, pancreatic juices release B12 from R-protein and hand it to intrinsic factor. This pairing allows B12 to be absorbed into cells, where it can then help maintain nerve cells and form healthy red blood cells.
A B12 deficiency typically involves a breakdown at one or more of these points on the way to absorption.
Without saliva, B12 will not bind to the saliva’s R-protein, and the body’s ability to absorb it is inhibited. And there are hundreds of different drugs that can cause dry mouth, resulting in too little saliva production. They include opioids, inhalers, decongestants, antidepressants, blood pressure drugs and benzodiazepines, like Xanax, used to treat anxiety.
The last three categories alone account for easily 100 million prescriptions in the U.S. each year.
Another potential contributor to B12 deficiency is low levels of stomach acid. Hundreds of millions of Americans take anti-ulcer medications that reduce ulcer-causing stomach acids. Researchers have firmly linked the use of these drugs to B12 deficiency – although that possibility may not outweigh the need for the medication.
Production of stomach acid can also decrease with aging. More than 60 million people in the U.S. are over age 60, and some 54 million are over the age of 65. This population faces a higher risk of B12 deficiency – which may be further increased by use of acid-reducing medications.
Production of gastric acid and intrinsic factor by the specialized parietal cells in the stomach is critical for B12 absorption to occur. But damage to the stomach lining can prevent production of both.
In humans, impaired stomach lining stems from gastric surgery, chronic inflammation or pernicious anemia – a medical condition characterized by fatigue and a long list of other symptoms.
While some health care providers routinely measure B12 and other vitamin levels, a typical well-check exam includes only a complete blood count and a metabolic panel, neither of which measures B12 status. If you experience potential symptoms of a B12 deficiency and also have one of the risk factors above, you should see a doctor to be tested. A proper lab workup and discussion with a physician are necessary to discover or rule out whether inadequate B12 levels could be at play.
In the case of my dog Scout, her symptoms led the vet to run two blood tests: a complete blood count and a B12 test. These are also good starting points for humans. Scout’s symptoms went away after a few months of taking oral B12 supplements that also contained an active form of the B vitamin folate.
In humans, the type of treatment and length of recovery depend on the cause and severity of the B12 deficiency. Full recovery can take up to a year but is very possible with appropriate treatment.
Treatment for B12 deficiency can be oral, applied under the tongue or administered through the nose, or it may require various types of injections. A B12 supplement or balanced multivitamin may be enough to correct the deficiency, as it was for Scout, but it’s best to work with a health care provider to ensure proper diagnosis and treatment.
This article is republished from The Conversation, an independent nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Diane Cress, Wayne State University. Like this article? subscribe to our weekly newsletter.
Diane Cress does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.