Vitamin B12 deficiency is a common health problem that can have serious consequences, but doctors often overlook it

For several months in the summer of 2022, my dog ​​Scout vomited at 3am almost every day. If you have a dog, you know the sound. And each time she gobbled up her mess before I could get to it, making diagnosing the cause difficult.

The vet and I eventually concluded that my hydrangeas were the source of the problem – but keeping Scout away from them didn’t work. She started looking tired all the time – very concerning in a typical hyper yellow Lab puppy.

Then one day Scout vomited a hairball – but not just any hairball. In dogs, hair normally passes easily through the digestive system, but this hairball was wrapped around a brillo pad that was too large to move through. Once this foreign object was removed, the vomiting ended overnight. However, Scout still needed treatment for another and surprising reason: the object had inhibited a step in her body’s absorption of vitamin B12. B12 is an essential nutrient involved in the proper functioning of blood cells, nerves and many other critical processes in the body.

I am a registered dietitian and teach nutrition and nutritional science to college students, yet I missed the B12 deficiency that caused my puppy’s fatigue. Doctors might as well be blind to people — even though B12 deficiency is a common health problem that affects an estimated 6% to 20% of the US population.

B12 is scarce in the diet and is only found in foods of animal origin. Fortunately, humans only need 2.4 micrograms of B12 each day, which is equivalent to one ten-millionth of an ounce — a very, very small amount. Without enough B12 in the body, overall health and quality of life are negatively affected.

An overhead view of an array of B12-containing foods, including oysters, fish, eggs, red meat, and more.
A range of vitamin B12 rich foods – all sourced from animals.
photo/iStock via Getty Images Plus

Signs and Symptoms

A primary symptom of B12 deficiency is fatigue – a degree of tiredness or exhaustion that is so profound that it affects daily activities.

Other symptoms are neurological and may include tingling in the extremities, confusion, memory loss, depression, and difficulty keeping balance. Some of these may be permanent if the vitamin deficiency is not addressed.

However, because there can be so many causes for these symptoms, health care providers may overlook the possibility of a B12 deficiency and not screen for it. Furthermore, having a healthy diet seems to rule out a vitamin deficiency. Example: Because I knew Scout’s diet was sound, I didn’t consider a B12 deficiency to be the cause of her problems.

How B12 is absorbed

Research has clearly shown that people following a plant-based diet should take B12 supplements in amounts typically provided by standard multivitamins. However, hundreds of millions of Americans who do consume B12 may also be at risk due to conditions that could interfere with their body’s absorption of B12.

B12 absorption is a complex multi-step process that begins in the mouth and ends at the end of the small intestine. When we chew, our food is mixed with saliva. When the food is swallowed, a substance in the saliva called R-protein — a protein that protects B12 from being destroyed by stomach acid — travels with the food to the stomach.

Specific cells in the stomach lining, called parietal cells, secrete two substances important for B12 absorption. One is stomach acid — it splits food and B12 apart, allowing the vitamin to bind to saliva’s R protein. The other substance, called intrinsic factor, mixes with the stomach contents and travels with them to the first part of the small intestine – the duodenum. Once in the duodenum, pancreatic juices release B12 from R protein and pass it on to intrinsic factor. This linkage allows B12 to be taken into cells, where it can then help maintain nerve cells and form healthy red blood cells.

A B12 deficiency is usually accompanied by a breakdown at one or more of these points on the way to absorption.

Dr. Darien Sutton explains the symptoms of B12 deficiency in this December 2021 segment of the ABC TV show “Good Morning America.”

Risk factors for B12 deficiency

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 medications that can cause dry mouth, resulting in low saliva production. They include opioids, inhalers, decongestants, antidepressants, blood pressure medications, and benzodiazepines, such as Xanax, which are used to treat anxiety.

The last three categories alone account for easily 100 million prescriptions in the US each year.

Another possible cause of B12 deficiency is low stomach acid. Hundreds of millions of Americans take ulcer medications that reduce the stomach acid that causes stomach ulcers. Researchers have firmly linked the use of these drugs to B12 deficiency — although that possibility may not outweigh the need for the medication.

Stomach acid production may also decrease with age. More than 60 million people in the US are over the age of 60 and about 54 million are over the age of 65. This population group is at a higher risk of B12 deficiency – which can be further increased by the use of acid-lowering drugs.

The production of gastric acid and intrinsic factor by the specialized parietal cells in the stomach is critical for B12 absorption. But damage to the stomach lining can prevent the production of both.

In humans, a compromised stomach lining results from gastric surgery, chronic inflammation, or pernicious anemia — a medical condition characterized by fatigue and a long list of other symptoms.

Another common culprit of B12 deficiency is inadequate pancreatic function. About one-third of patients with poor pancreatic function develop a B12 deficiency.

And finally, metformin, a drug used by about 92 million Americans to treat type 2 diabetes, has been linked to B12 deficiency for decades.

Treatment for B12 deficiency

While some health care providers routinely measure B12 and other vitamin levels, a typical well-check exam only includes a complete blood count and metabolic panel, neither of which measure B12 status. If you experience possible symptoms of a B12 deficiency and also have any of the above risk factors, you should see a doctor to get tested. A good laboratory test and consultation with a doctor are necessary to discover or rule out whether there may be insufficient B12 levels.

In my dog ​​Scout’s case, her symptoms prompted 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 resolved after a few months of taking oral B12 supplements that also contained an active form of the B vitamin folic acid.

In humans, the type of treatment and the length of recovery depends on the cause and severity of the B12 deficiency. Full recovery can take up to a year, but is very possible with proper treatment.

Treatment for B12 deficiency may be oral, applied under the tongue, or given through the nose, or different types of injections may be required. A B12 supplement or balanced multivitamin may be enough to correct the deficiency, as with Scout, but it’s best to work with a healthcare provider to ensure proper diagnosis and treatment.

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