http://lpi.oregonstate.edu/infocente...ns/vitaminB12/

Neurologic symptoms:
The neurologic symptoms of vitamin B12 deficiency include
numbness and tingling of the arms and more commonly the legs,
difficulty walking,
memory loss,
disorientation, and dementia, with or without mood changes.

Although the progression of neurologic complications is generally gradual, they are not always reversible with treatment of vitamin B12 deficiency, especially if they have been present for a long time. Neurologic complications are not always associated with megaloblastic anemia, and are the only clinical symptom of vitamin B12 deficiency in about 25% of cases (5).

Although vitamin B12 deficiency is known to damage the myelin sheath covering cranial, spinal, and peripheral nerves, the biochemical processes leading to neurological damage in B12 deficiency are not well understood (2).


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Alzheimer's disease and dementia

Individuals with Alzheimer's disease often have low blood levels
of vitamin B12.

One study found lower vitamin B12 levels in the cerebrospinal fluid of patients with Alzheimer's disease than in patients with other types of dementia, though blood levels of vitamin B12 did not differ (15).

The reason for the association of low vitamin B12 status with Alzheimer's disease is not clear. Vitamin B12 deficiency, like folate deficiency, may lead to decreased synthesis of methionine and S-adenosylmethionine, adversely affecting methylation reactions essential for the metabolism of components of the myelin sheath of nerve cells, as well as neurotransmitters.


Moderately increased homocysteine levels, as well as decreased folate and vitamin B12 levels have also been associated with Alzheimer's disease and vascular dementia. A case-control study of 164 patients with dementia of Alzheimer's type included 76 cases in which the diagnosis of Alzheimer's disease was confirmed by examination of the brain cells after death (16). Compared to 108 control subjects without evidence of dementia, subjects with dementia of Alzheimer's type and confirmed Alzheimer's disease had higher blood homocysteine levels and lower folate and vitamin B12 levels. Measures of general nutritional status indicated that the association of increased homocysteine levels and diminished vitamin B12 status with Alzheimer's disease was not due to dementia-related malnutrition. Low serum vitamin B12 (< 150 pmol/L) or folate (< 10 nmol/L) levels were associated with a doubling of the risk of developing Alzheimer's disease in 370 elderly men and women followed over 3 years (17). In a sample of 1092 men and women without dementia followed for an average of 10 years, those with higher plasma homocysteine levels at baseline had a significantly higher risk of developing Alzheimer's disease and other types of dementia (18). Those with plasma homocysteine levels greater than 14 mmol/L had nearly double the risk of developing Alzheimer's disease.

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references : micronutrient information center: Linus Pauling Institue

http://lpi.oregonstate.edu/infocente...2/b12refs.html

NEURODEGENERATIVE ILLNESS
http://lpi.oregonstate.edu/infocente...eurodegen.html

Great post about one of my favorite topics. On the same subject, may I add ~
eMedicine link on vitamin B12 associated neurological diseases:

eMedicine on Nutritional Neuropathy

AAFP on Vitamin B12 Deficiency

Subacute combined degeneration: clinical, electrophysiological, and magnetic resonance imaging findings JNNP

and on B12 deficiency/Alzheimers:

High-dose vitamin B12 for at-home prevention and reversal of Alzheimer's disease and other diseases - Townsend Letter May 2006

Familial Alzheimer's disease and vitamin B12 deficiency - Age and Ageing July 1994

Dear jccglutenfree,
thank you soooooooooo much for all the informational links