OVERVIEW
Vitamin B12 is important for neural function and formation of DNA for cellular regeneration.
Vitamin B12 and Vitamin B9 (folate) often work together and often must be supplemented together since only supplementing one may "mask" symptoms of deficiency of the other.
FUNCTIONS
Important functions of Vitamin B12 include:
- Required for carbohydrate metabolism and neural function.
- Required for many biochemical synthesis processes that transfer one carbon from one molecule to another (methylation).
- Required for DNA synthesis.
- Required for many detoxification reactions.
- Required to maintain homocystene levels low.
SYMPTOMS OF DEFICIENCY
Deficiency symptoms may include [AAFP]:
- Macrocytic anemia and other blood dyscrasias.
- Weakness, fatigue, brain fog.
- Cognitive impairment or psychosis.
- Nerve damage: peripheral neuropathy, loss of reflexes, proprioception and vibratory sense.
- Gait abnormalities.
- Loss of sense of smell.
Dosage:
- Optimum Dose (Adults): 100-500mcg/day [Marz1999, pg 221]
- Typical USA Daily Intake: In the United States, the prevalence of vitamin B12 deficiency is approximately 6% in persons younger than 60 years, and nearly 20% in those older than 60 years. Deficiency prevalence may be as high as 80% in some parts of the world [AAFP].
DETAILS
Although Vitamin B12 is water soluble, its absorption from food requires a unique process, in which the stomach secretes a small protein called "intrinsic factor", which helps transport Vitamin B12 across the gut barrier into the blood in the small intestines. A rare disorder called "pernicious anemia" occurs when the body is unable to make intrinsic factor (due to an autoimmune condition). Much more commonly, production of intrinsic factor can be blocked by antacid medications such as proton-pump inhibitors and H-2 blockers. In these cases, oral Vitamin B12 is poorly absorbed, but can be administered via other routes, such as sub-lingual, IM, or IV.
GENETICS
Some people have a genetic predisposition to require more Vitamin B12 than others.
SOURCES
The main sources of Vitamin B12 are animal products, and "fortified" non-animal products which contain the synthetic form called cyanocobalamin.
Bacteria in our large intestine can make Vitamin B12, but unfortunately we cannot absorb the Vitamin B12 from our large intestine (we absorb any available Vitamin B12 in our small intestine, which flows down into the large intestine.
Bacteria in the soil can make Vitamin B12, but only if the trace mineral cobalt is present; with modern agricultural practices this does not provide a reliable source [aminomantra].
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