For several months in the summer of 2022, my dog Scout vomited at 3 in the morning almost every day. If you have a dog, you know the sound. And every time, she ate the mess she made before I got there, making it hard to diagnose the cause.
The vet and I eventually decided that my hydrangeas were the source of the problem; but keeping Scout away from them did not work. She began to appear tired all the time, something very concerning in a typically hyperactive Labrador retriever.
Then one day Scout vomited up a furball, but not just any furball. In dogs, hair normally passes easily through the digestive system. But this ball of fur was wrapped around a cleaning rag that was too big to move.
Once this foreign object was removed, the overnight vomiting stopped. However, Scout still needed treatment for a different and surprising reason: the object had inhibited a step in her body’s absorption of vitamin B12.
Importance of B12
B12 is an essential nutrient involved in the proper function of blood cells, nerves, and many other critical processes in the body. I am a registered nutritionist and I teach nutrition and food science to college students. But I still missed the B12 deficiency that was causing my pup’s fatigue.
Doctors can easily ignore it in people, even though B12 deficiency is a common health problem, affecting approximately 6% to 20% of the US population. Vitamin B12 is in short supply in the diet and is it is found only in foods of animal origin.
Fortunately, humans only need 2.4 micrograms of B12 per day, a very, very small amount. Without an adequate amount of vitamin B12 in the body, general health and quality of life are negatively affected.
Signs and symptoms
One of the main symptoms of vitamin B12 deficiency is fatigue, a level of tiredness or exhaustiveness so profound that it affects activities of daily living. Other symptoms are neurological and can include tingling in the extremities, confusion, memory loss, and depression, and difficulty to maintaining balance. Some of these may be permanent if the vitamin deficiency is not addressed.
However, since there can be so many causes for these symptoms, doctors may miss the possibility of a vitamin B12 deficiency and fail to detect it. Also, having a healthy diet seems to rule out any vitamin deficiencies. Case in point: Since I knew Scout’s diet was good, I did not consider vitamin B12 deficiency the source of her problems.
How is vitamin B12 absorbed?
The research is clear that people who eat plant-based diets should take B12 supplements in amounts normally provided by standard multi-vitamins. However, hundreds of millions of Americans who consume B12 may also be at risk due to conditions that could be hindering the absorption of B12 into their body.
A tired woman
B12 absorption is a complex, multi-step process that begins in the mouth and ends at the other end of the small intestine. When we chew, our food is mixed with saliva. When food is swallowed, a substance in the saliva called the R protein. It is a protein that protects B12 from being destroyed by stomach acid, travels to the stomach along with the food.
Specific cells in the stomach lining, called parietal cells, secrete two substances that are important for B12 absorption. One is stomach acid: it separates food and vitamin B12, allowing the vitamin to bind to the R protein in saliva.
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 liberate B12 from the R protein and deliver 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 vitamin B12 deficiency usually involves a breakdown at one or more of these points on the path to absorption.
Risk factors for B12 deficiency
Without saliva, vitamin B12 will not bind to the R protein in saliva and the body’s ability to absorb it is inhibited. And there are hundreds of different medications that can cause dry mouth, resulting in saliva production that is too low.
They include opioids, inhalants, decongestants, antidepressants, blood pressure medications, and benzodiazepines, such as Xanax, which are used to treat anxiety. Another potential contributor to vitamin 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 strongly linked the use of these drugs with vitamin B12 deficiency, although that possibility may not outweigh the need for the drug.
Stomach acid production can also decrease with aging. 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 faces a higher risk of vitamin B12 deficiency, which can be further increased by the use of acid-reducing medications.
The production of gastric acid and intrinsic factor by specialized parietal cells in the stomach is critical for B12 absorption to occur. But damage to the stomach lining can prevent the production of both. In humans, deterioration of the stomach lining is due to gastric surgery, chronic inflammation or pernicious anemia, a medical condition characterized by fatigue, and a long list of other symptoms.
Another common culprit for vitamin B12 deficiency is improper function of the pancreas. About a third of patients with a malfunctioning pancreas develop a vitamin B12 deficiency. And finally, metformin, a drug used by around 92 million Americans to treat type 2 diabetes, has been associated with vitamin B12 deficiency for decades.
Treatment for B12 deficiency
While some doctors routinely measure levels of B12 and other vitamins, a routine checkup includes only a complete blood count and metabolic panel, neither of which measure B12 status. If you are experiencing potential symptoms of a B12 deficiency and also have one of the risk factors above, you should see a doctor for testing.
A proper laboratory analysis and discussion with a doctor is needed 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 resolved 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 vitamin B12 deficiency. Full recovery can take up to a year, but it is quite possible with proper treatment.
Treatment for vitamin B12 deficiency can be taken orally, applied under the tongue or administered through the nose, or it may require various types of injections. A vitamin B12 supplement or balanced multivitamin may be enough to correct the deficiency, as it was for Scout, but it’s best to see a doctor to ensure proper diagnosis and treatment.