Vitamin B12 deficiency: Symptoms and absorption mechanisms

Vitamin B12 plays a critical role in blood formation and the nervous system. Because plant-based foods are not reliable sources, individuals on plant-based diets require special attention to prevent deficiency.

Symptoms of a deficiency can include fatigue, dizziness, paleness, heart palpitations, and shortness of breath. Neurological warning signs are particularly significant, including numbness or tingling in the hands and feet, balance disorders, memory loss, and confusion. According to Oregon State University, tingling in the feet is the most common neurological symptom and can be the only clinical sign in approximately 25 percent of cases. Notably, neurological damage may occur even without detectable anemia in standard blood tests.

Effective absorption requires a coordinated process between the stomach and small intestine. Stomach acid releases the vitamin from food proteins, which then binds to the intrinsic factor produced by the stomach lining to allow absorption in the small intestine. Absorption can be hindered by conditions such as autoimmune gastritis, which affects the production of intrinsic factor, or intestinal diseases like celiac disease and Crohn's disease. Surgical removal or bypass of parts of the stomach or small intestine can also impede the body's ability to absorb the nutrient.