Vitamin B12: Why This Essential Nutrient Deserves Your Attention

Vitamin B12 (cobalamin) is a water-soluble vitamin vital for DNA synthesis, red blood cell formation, and neurological function. Despite being required in only microgram quantities, a deficiency can result in serious and often underdiagnosed health consequences.

From fatigue and brain fog to irreversible nerve damage, understanding B12's role in health is crucial for both clinicians and the general public—especially given the growing prevalence of plant-based diets, gastrointestinal disorders, and age-related malabsorption.

What Is Vitamin B12 and Why Is It Important?

Vitamin B12 serves as a cofactor in key enzymatic reactions that regulate:

• DNA synthesis (via methionine synthase)

• Myelin production in the nervous system

• Homocysteine metabolism (linked to cardiovascular health)

• Red blood cell maturation in bone marrow

• It is naturally found in animal-derived foods like meat, fish, dairy, and eggs. Since the body does not produce it, B12 must be obtained through diet or supplementation.

Who Is at Risk of B12 Deficiency?

Despite being widely available in food, B12 deficiency is common and often overlooked, especially in certain populations:

• Older adults (due to decreased intrinsic factor and stomach acid)

• Vegetarians and vegans (lack of dietary intake)

• Patients with gastrointestinal disorders (e.g., Crohn’s, celiac, atrophic gastritis)

• Individuals on long-term medications, such as:

• Proton pump inhibitors (PPIs)

• Metformin

• Deficiency is also seen in pernicious anemia, an autoimmune condition that impairs B12 absorption by attacking intrinsic factor–producing cells.

Symptoms of Vitamin B12 Deficiency

The symptoms of B12 deficiency can be subtle and nonspecific at first but may progress to significant complications:

• Persistent fatigue or weakness

• Numbness or tingling in hands and feet

• Memory loss, brain fog, or confusion

• Pale or jaundiced skin

• Glossitis (inflamed tongue)

• Balance or coordination issues

• Irritability or mood changes

• Neurological symptoms can occur even in the absence of anemia, making clinical suspicion essential.

Diagnosis and Lab Testing

Early detection is key. Common tests include:

• Serum Vitamin B12 levels (<200 pg/mL often indicates deficiency)

• Methylmalonic acid (MMA) – more sensitive marker

• Homocysteine levels – elevated in B12 or folate deficiency

• Complete blood count (CBC) – may show macrocytic anemia

• Treatment: Supplementation and Dietary Strategies

Treatment depends on the cause and severity of deficiency:

• Oral supplements (1,000–2,000 mcg/day) are effective in mild deficiency

• Intramuscular injections are used in:

• Pernicious anemia

• Severe neurological symptoms

• Malabsorption cases

Dietary sources include:

• Liver, shellfish, and red meat (highest concentrations)

• Eggs and dairy (moderate sources)

• Fortified plant-based milks, cereals, and nutritional yeast

• Vegans should routinely supplement B12 to avoid deficiency.

Emerging Research: B12 and Cognitive Health

Recent studies have linked low B12 levels with cognitive decline and increased risk of dementia, particularly in elderly populations. Although causality remains debated, early correction of deficiency appears to slow progression of certain neuropsychiatric symptoms.

There is also interest in B12’s role in homocysteine regulation, with implications for cardiovascular health and pregnancy outcomes.

Conclusion

Vitamin B12 is an essential yet frequently underestimated nutrient. Its deficiency can have profound hematological and neurological consequences, many of which are reversible if detected early. As clinical awareness grows, especially among at-risk populations, proactive screening and timely supplementation can help safeguard long-term health and cognitive function.

Sources

• O’Leary F, Samman S. Vitamin B12 in health and disease. Nutrients. 2010.

• National Institutes of Health – Office of Dietary Supplements. Vitamin B12 Fact Sheet.

• https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/

• Stabler SP. Clinical practice: Vitamin B12 deficiency. N Engl J Med. 2013.

• Smith AD, Refsum H. Vitamin B12 and cognition in the elderly. Am J Clin Nutr. 2009.