For several months during the summer of 2022, my dog Scout vomited almost every day at 3 in the morning. If you have a dog, you know the sound. And each time, she’d eat her shit before I even got to it, making it hard to pinpoint the cause.
The vet and I eventually settled on my hydrangeas as the source of the problem – but keeping Scout away from them didn’t work. He seemed tired all the time – overly anxious typically in hyper yellow lab pups.
Then one day Scout vomited up a hairball — but not just any hairball. In dogs, hair usually passes easily through the digestive tract, but this hairball wrapped around a Brillo pad was just too big. Once this foreign object was removed, the overnight vomiting ceased. Scout still needed treatment, however, for a different and surprising reason: The object had blocked 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 vital processes in the body.
I’m a registered dietitian, and I teach nutrition and food science to college students, but I still remembered the B12 deficiency that was causing my puppy’s fatigue. Doctors can easily be blind to this in people – even though B12 deficiency is a common health problem affecting an estimated 6% to 20% of the US population.
B12 is rare in the diet, and is only found in foods from animal sources. Fortunately, humans only need 2.4 micrograms of B12 per day, which is about 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.
Signs and symptoms
A primary symptom of B12 deficiency is fatigue — a level of tiredness or fatigue so severe that it affects activities of daily living.
Other symptoms are neurological and may include tingling in the extremities, confusion, memory loss, depression, and difficulty maintaining balance. Some of these can be permanent if the vitamin deficiency is not corrected.
Although these symptoms can have many causes, health care providers may overlook the possibility of B12 deficiency and fail to test for it. In addition, any vitamin deficiencies can be overcome by consuming a healthy diet. Case in point: Because I knew Scout’s diet was good, I didn’t consider a B12 deficiency to be the source of her problems.
How is B12 absorbed
Research is clear that people who consume a plant-based diet should generally take B12 supplements in the amount provided by a standard multivitamin. However, the hundreds of millions of Americans who consume B12 may also be at risk due to conditions that may hinder their bodies’ absorption of B12.
B12 absorption is a complex multistep process that begins in the mouth and ends at the distal end of the small intestine. When we chew, our food gets mixed with saliva. When food is ingested, a substance in saliva called R-protein – a protein that protects B12 from being destroyed by stomach acid – travels with the food to the stomach.
Specialized cells in the lining of the stomach, called parietal cells, secrete two substances that are important for B12 absorption. One is stomach acid – this breaks down food and B12, allowing the vitamin to bind to the R-protein of saliva. Another substance, called intrinsic factor, mixes with the contents of the stomach and travels with them into the duodenum – the first part of the small intestine. Once in the duodenum, the pancreatic juice releases B12 from the R-protein and passes it on to intrinsic factor. This coupling allows B12 to be absorbed into cells, where it may help maintain nerve cells and form healthy red blood cells.
B12 deficiency usually involves a breakdown at one or more of these points along the way to absorption.
Risk factors for B12 deficiency
Without saliva, B12 will not be able to 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, which results in too little saliva being produced. They include opioids such as Xanax, inhalers, decongestants, antidepressants, blood pressure drugs, and benzodiazepines used to treat anxiety.
The last three categories alone easily account for 100 million prescriptions each year in the US.
Another possible contributor to B12 deficiency is low levels of stomach acid. Millions of Americans take anti-ulcer drugs that reduce the stomach acid that causes ulcers. Researchers have strongly linked the use of these drugs to B12 deficiency – although this possibility may not outweigh the need for the drug.
The production of stomach acid can also decrease with age. More than 60 million people in the US are over the age of 60, and some 54 million are over the age of 65. There is a high risk of B12 deficiency in this population – which may be exacerbated by the use of acid-reducing medications.
The production of gastric acid and intrinsic factor by specialized parietal cells in the stomach is important for B12 absorption to occur. But damage to the stomach lining can stop the production of both.
In humans, the 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.
Another common culprit of B12 deficiency is insufficient function of the pancreas. About one-third of patients with poor pancreas function develop B12 deficiency.
And finally, metformin, a drug used by some 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-screened test includes only a complete blood count and a metabolic panel, neither of which measures B12 status. Is. If you experience possible symptoms of B12 deficiency and also have one of the above risk factors, you should visit a doctor for testing. A proper lab workup and discussion with a physician is necessary to determine whether B12 levels may be insufficient.
In the case of my dog Scout, his symptoms prompted the vet to run two blood tests: a complete blood count and B12 test. These are good starting points for humans as well. Scout’s symptoms went away after a few months of taking an oral B12 supplement that also contained an active form of the B vitamin folate.
In humans, the type of treatment and recovery period depend 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 administered through the nose, or it may require various types of injections. B12 supplementation or a balanced multivitamin may be sufficient to correct the deficiency, as was the case for Scout, but it is best to work with a health care provider to ensure proper diagnosis and treatment.