Vitamin B12 Deficiency and Memory Impairment

Neurological Mechanisms

Vitamin B12 is essential for preserving the myelin sheath around neurons, which is critical for proper nerve conduction and neurological function 2
B12 serves as a cofactor for methionine synthase, which transfers methyl groups to form methionine from homocysteine, and for methyl malonyl-CoA mutase in the synthesis of succinyl CoA - both pathways are crucial for brain metabolism 3
B12 deficiency leads to elevated homocysteine levels (hyperhomocysteinemia), which has been associated with cognitive decline and is considered a potential mechanism in the development of dementia 4

Cognitive difficulties, particularly concentration problems and short-term memory loss, are common symptoms of vitamin B12 deficiency, according to the British Medical Journal 1
Vitamin B12 deficiency should be considered in patients presenting with memory problems, especially in those with risk factors such as older age, vegetarian/vegan diets, or use of medications like metformin, as recommended by the British Medical Journal and Clinical Nutrition 1, 3

B12 deficiency impairs one-carbon metabolism, which is crucial for DNA synthesis and repair in neuronal cells, as reported in Nutrition Research Reviews 5
The vitamin is essential for mitochondrial metabolism in brain cells, which is necessary for energy production in neurons, according to Clinical Nutrition 3
B12 deficiency leads to functional folate deficiency, creating a "methyl trap" where 5-methyltetrahydrofolate accumulates and cannot participate in one-carbon transfer reactions, as described in Nutrition Research Reviews 5