For several months in the summer of 2022, my dog Scout threw up at 3 a.m. most days. If you have a dog, you know the sound. And each time, she would gobble up her mess before I could get to it, making it difficult to diagnose the cause.
The vet and I ultimately singled out my hydrangeas as the source of the problem, but pushing Scout away from them didn’t work. She started to look tired all the time – which is very worrying in a typically hyper yellow Lab pup.
Then one day, Scout threw up a hairball – but not just any hairball. In dogs, hair normally passes easily through the digestive system, but this ball of hair was wrapped around a brillo pad that was too big to pass through. Once this foreign object was removed, the nighttime vomiting ended. However, Scout still needed treatment for a different and surprising reason: the item had inhibited a step in his 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 dietitian and I teach nutrition and food science to students, but I still missed the vitamin B12 deficiency that was causing my pup to be tired. Physicians can just as easily be blind in humans – even though B12 deficiency is a common health condition that affects around 6% to 20% of the American population.
Vitamin B12 is rare in the diet and only found in foods of animal origin. Fortunately, humans only need 2.4 micrograms of B12 per day, which equals one ten-millionth of an ounce – a very, very small amount. Without adequate vitamin B12 in the body, overall health and quality of life are negatively affected.
Signs and symptoms
One of the main symptoms of a B12 deficiency is fatigue – a level of tiredness or exhaustion so profound 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 them can be permanent if the vitamin deficiency is not treated.
However, because there can be so many causes for these symptoms, healthcare providers may overlook the possibility of a B12 deficiency and not screen for it. Also, having a healthy diet can seem to rule out any vitamin deficiency. Example: Because I knew Scout’s diet was healthy, I did not consider a vitamin B12 deficiency to be the source of her problems.
How B12 is Absorbed
The research is clear that people who consume plant-based diets must take B12 supplements in amounts typically provided by standard multivitamins. However, hundreds of millions of Americans who consume B12 may also be at risk due to conditions that could interfere with their body’s absorption of B12.
The absorption of B12 is a complex multi-step process which begins in the mouth and ends at the end of the small intestine. When we chew, our food mixes with saliva. When food is swallowed, a substance in the saliva called R-protein – a protein that protects vitamin B12 from being destroyed by stomach acid – travels to the stomach with food.
Specific cells in the stomach lining, called parietal cells, secrete two substances important for the absorption of B12. One is stomach acid – it separates food and vitamin B12, allowing the vitamin to bind to protein R in saliva. The other substance, called intrinsic factor, mixes with the contents of the stomach and travels with it to the first part of the small intestine, the duodenum. Once in the duodenum, pancreatic juices release B12 from the R protein and pass it on to intrinsic factor. This pairing allows B12 to be taken up into cells, where it can then help maintain nerve cells and form healthy red blood cells.
A B12 deficiency usually involves a breakdown at one or more of these points on the absorption pathway.
Risk factors for vitamin B12 deficiency
Without saliva, B12 does 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 too little saliva production. They include opioids, inhalers, decongestants, antidepressants, blood pressure medication and benzodiazepineslike Xanax, used to treat anxiety.
The last three categories alone easily account for 100 million prescriptions in the United States each year.
Another potential contributor to vitamin B12 deficiency is low stomach acid. Hundreds of millions of Americans take anti-ulcer drugs which reduce stomach acids causing ulcers. Researchers have firmly established a link between the use of these drugs and B12 deficiency – although this possibility may not compensate for the need for medication.
Production of stomach acid may also decrease with age. More than 60 million people in the United States are over 60and some 54 million are over 65. This population faces a higher risk of B12 deficiency – which can be further increased by the use of antacid medications.
The production of gastric acid and intrinsic factor by the specialized parietal cells of the stomach is essential for the absorption of B12. But damage to the stomach lining can prevent the production of both.
In humans, the alteration of the stomach lining comes from gastric surgery, chronic inflammation or pernicious anemia – a medical condition characterized by fatigue and a long list of other symptoms.
Treatment of B12 deficiency
While some healthcare providers routinely measure levels of B12 and other vitamins, a typical wellness checkup exam includes only a complete blood count and metabolic panel, which measure neither. the other the B12 status. If you have potential symptoms of vitamin B12 deficiency and also have any of the above risk factors, you should see a doctor to get tested. Proper lab workup and discussion with a physician is necessary to discover or rule out whether inadequate levels of B12 might be involved.
In the case of my dog Scout, his symptoms led the vet to perform two blood tests: a complete blood count and a B12 test. They are also good starting points for humans. Scout’s symptoms resolved after a few months of taking oral vitamin B12 supplements that also contain an active form of vitamin B folate.
In humans, the type of treatment and recovery time depend on the cause and severity of vitamin B12 deficiency. Full recovery can take up to a year, but is entirely possible with proper treatment.
Treatment of B12 deficiency can be oral, applied under the tongue or administered through the nose, or it can require various types of injections. A B12 supplement 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.