Cobalamin - Vitamin B12

Vitamin B12 is a member of the B-complex vitamins. It is water-soluble, cobalt-containing and stable to heat. Vitamin B12 is necessary for the formation of blood corpuscles, nerve sheaths, and is involved in protein, fat, and carbohydrate metabolism.

Absorption decreases with age and with deficiencies of vitamin B6, calcium, and iron. After absorption, vitamin B12 is bound to serum proteins (globulins) and is transported in the bloodstream to tissues.

The main cobalamins in humans are hydroxocobalamins, adenosylcobalamin and methylcobalamin, the last two being the active coenzyme forms.

FOOD SOURCES

Red meat and offal, blue cheese, seafood, dairy products, eggs, Loss of activity from cooking is approximately 70%. Vitamin B12 slowly loses its activity when exposed to light, oxygen, and acid or alkali environments.

SUPPLEMENTATION

Cyanocobalamin is widely used as a supplement because of its availability and stability, and is transformed into the active factors in the body. Vitamin B12 is produced commercially from bacterial fermentation.

SIGNS OF DEFICIENCY

Appetite loss, bleeding gums, brain damage resembling schizophrenia, confusion, depression, difficulty in walking and speaking, difficulty walking, diminished reflex response and sensory perception, fatigue, feeling of deadness, headache, jerking of the limbs, menstrual disorders, nausea, nervousness, neuritis, numbness or stiffness, pale gums, lips and tongue, pins-and-needles or hot-or-cold sensations, poor memory, shooting pains, shortness of breath, sore mouth, sore tongue, soreness and weakness in the legs and arms, unpleasant body odor, weight loss, yellow eyes and skin. Vegetarians are usually deficient in vitamin B12. Laxatives reduce the levels of vitamin B12.

SIGNS OF TOXICITY

There are no known signs of toxicity from vitamin B12 and a study of high doses of 1mg/day (500 times the RDA) for 5 years has shown no adverse effects.

DAILY REQUIREMENT

5-10mcg.