With its reputation for improving mood and energy, vitamin B12 is the most well-known of the vitamin B complex. So why is B12 so important? We can answer this question by understanding the impact and consequences of the body during vitamin B12 deficiency.
What is vitamin B12?
Vitamin B12 is one of the essential nutrients for metabolism. In nutritional speak, this means that our bodies cannot produce vitamin B12, so we must obtain it from the foods we eat.
Vitamin B12, or cobalamin, is a large, water-soluble, complex molecule that is a necessary assistant for DNA synthesis in every cell of the human body. It shares this important role with vitamin B9 (or folic acid).
Red blood cells and nerve cells, two of the most abundant cell types, rely on B12 for their basic functioning. In particular, B12 is critical to two processes in these cells:
- the creation of myelin, the insulating sheath that surrounds nerve cells and helps them accelerate their signals;
- the maturation of red blood cells (RBCs), the delivery trucks of the body's oxygen transport system, within the bone marrow.
What are the risks of low B12 levels?
Vitamin B12 is obtained in the diet primarily through animal products: beef, fish, pork, chicken, liver, milk, and eggs. Therefore, those who follow a vegan diet must be mindful of their B12 intake. To help vegans avoid the risk of B12 deficiency, the United States and other developed countries require B12 to be added to some staple foods of a vegan diet like soy and almond products, as well as breakfast cereals.
Weight loss surgery is another significant risk factor for vitamin B12 deficiency. The most common type of this surgery (called gastric bypass surgery), creates a small stomach pouch and digested food moves from this pouch to the middle of the small intestine.
The body's B12 "uploading site" is also in the small intestine, and the "password" for the upload, is a protein called intrinsic factor made in the stomach. Without it, B12 passes straight through the digestive tract, unavailable to the bloodstream for the body to use.
So, even if you get enough B12 from your diet, you could be at risk of B12 deficiency if:
- your stomach can't produce intrinsic factor
- your small intestine can't recognize intrinsic factor
Since gastric bypass surgery alters the anatomy and function of both the stomach and small intestine, surgeons typically recommend lifetime B12 supplementation for patients after the procedure.
Others at risk for B12 deficiency include:
- Infants (either from genetic metabolic errors, poor nutrition, or breastfeeding from vegan mothers)
- The elderly (who make less stomach acid and thus less intrinsic factor)
- Patients who have had digestive system surgery
- Residents of developing countries
- People with low socioeconomic status
Most blood cells are produced in the nutrient-rich bone marrow, and without sufficient B12, the bone marrow produces far fewer healthy red blood cells (RBCs). These vitamin B12-lacking RBCs are large, undeveloped, and unable to deliver oxygen to tissues and organs efficiently. This lack of healthy RBCs leads to a type of anemia called megaloblastic anemia.
When megaloblastic anemia is due to a lack of intrinsic factor produced in the stomach, it is called pernicious anemia.
Like all types of anemia, both megaloblastic and pernicious anemia result in poor oxygen delivery to cells — especially those with high oxygen requirements, such as cells in the heart, brain, and exercising muscle.
Symptoms of both types of anemia are similar to the other more common types of anemia:
- Rapid heartbeat (to compensate for the lack of oxygen)
- Shortness of breath
- Pale skin
When doctors suspect one of these types of anemia, the first step is to confirm that the diagnosis is correct. Doctors do this by measuring B12 and folic acid levels in the bloodstream, and by checking the shapes and sizes of red blood cells and related white blood cells.
Pernicious anemia can be detected by using blood tests that detect the presence of intrinsic factor and the presence of the stomach cells that make it.
Peripheral Neuropathy: I've Got A Funny Feeling About This
The other major clinical manifestation of vitamin B12 deficiency stems from its role in nerve cell development. Without the myelin that vitamin B12 helps produce, nerve cells send signals that are slow, inconsistent, messy, and communication between these cells dramatically suffers.
Peripheral nerve cells — which send signals to and from parts of the body farther away from the brain, like hands and feet — are particularly affected when adequate levels of B12 are not present. The name of this condition is peripheral neuropathy, literally meaning "suffering nerves."
Symptoms of peripheral neuropathy include:
- Numbness and tingling in the hands and feet
- Pinprick sensations in the extremities.
- Trouble walking
When a clinical exam reveals neuropathic symptoms, the diagnosis can be confirmed using similar methods to the process used for diagnosing B12 deficiency in anemia.
Common ways of addressing B12 Deficiency include...
Treating B12 deficiency can be accomplished through dietary supplementation or by B12 injection. Injections are often necessary for those who have pernicious anemia since, in this condition, B12 cannot be absorbed from the digestive tract.
If you've taken steps to improve your health through weight loss surgery or adhering to a vegan diet, it may seem like a strange irony that you are at risk for a nutritional deficiency.
With proper attention, supplementation, and prompt action, however, you can continue your pursuit of a healthy life without the danger of a vitamin B12 deficit, and enjoy the benefits of B12 supplementation.
Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on Folate, Other B Vitamins, and Choline. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington (DC): National Academies Press (US); 1998.
Aslinia F, Mazza JJ, Yale SH. Megaloblastic anemia and other causes of macrocytosis [published correction appears in Clin Med Res. 2006 Dec;4(4):342]. Clin Med Res. 2006;4(3):236–241. https://www.nhlbi.nih.gov/health-topics/pernicious-anemia
Ekabe CJ, Kehbila J, Abanda MH, Kadia BM, Sama CB, Monekosso GL. Vitamin B12 deficiency neuropathy; a rare diagnosis in young adults: a case report. BMC Res Notes. 2017;10(1):72.
Guez S, Chiarelli G, Menni F, Salera S, Principi N, Esposito S. Severe vitamin B12 deficiency in an exclusively breastfed 5-month-old Italian infant born to a mother receiving multivitamin supplementation during pregnancy. BMC Pediatr. 2012;12:85.