Vitamin B12 Methylcobalamin and Cyanocobalamin

Vitamin B12 is a water soluble vitamin and plays a key role for proper brain, heart, nervous system function, red blood cell formation and DNA synthesis.

Vitamin B12 is mainly found in animal foods such as meats, eggs, fish and dairy products. This is why taking a B12 supplement is highly recommended for anyone who's on a vegetarian or vegan diet in order to prevent deficiency. Evidence also indicates benefits for diabetics in preventing neuropathy (tingling, numbness in extremeties).

Applied Health's Methylcobalamin B12 is the most potent form of Vitamin B12 available today. More information on Sublingual Methylcobalamin B12

Description

Vitamin B-12 is a component of the water-soluble vitamin B-Complex. It is essential for normal growth, nucleic acid synthesis, protein and lipid synthesis, and the maintenance of epithelial cells and the nervous system, which is why it has been proven beneficial for diabetes sufferers.

Vitamin B-12 was given the name cobalamin because of the presence of cobalt. The active form of the vitamin is hydroxyocobalamin, and the vitamin is produced commercially as cyanocobalamin and methylcobalamin, the most bioavailable form of the vitamin.
 

Method of Action

Calcium is necessary for the proper absorption of vitamin B-12. However, the vitamin is poorly absorbed from the intestinal tract unless a mucoprotein intrinsic factor is present. This intrinsic factor is part of the gastric juices and assists in absorption by binding to vitamin B-12, which helps attach the vitamin to a receptor in the membranes of the lower small intestine. The vitamin is then transported into the cells.

Vitamin B-12 is transported in the bloodstream bound to transcobalamin I and II. In this way it circulates to the tissues, and is concentrated in the liver and, to some extent, the kidneys. Vitamin B-12 is then released as needed to other tissues of the body and to bone marrow.

Vitamin B-12 is involved in nucleic acid synthesis as well as protein, fat, and carbohydratemetabolism. Its primary function is the removal and transfer of methyl groups. In folacin metabolism a methyl group is removed by vitamin B-12 to form the active species tetrahydrofolate. Vitamin B-12 is also essential for the normal metabolism and growth of all cells, especially those of the gastrointestinal tract, bone marrow, and nervous system tissues. It has been reported that vitamin B-12 assists in maintaining hormone balance.

Absorption appears to decrease with aging, iron deficiency, and vitamin B-6 deficiency. Tobacco, alcohol, coffee, and laxatives prevent absorption of the vitamin. Vitamin B-12 is destroyed by heating, acid, or alkali. Vitamin B-6, vitamin B-Complex, choline, inositol, vitamin C, potassium, and sodium assist absorption. Absorption increases during pregnancy.
 

Properties & Uses

Vitamin B-12 has been promoted as a treatment for night blindness, psoriasis, warts, problems related to menopause, and general malaise. However, no scientific evidence suggests these problems result from a lack of vitamin B-12, or they can be cured by its use. Currently the only clinical use for vitamin B-12 is to treat a metabolic defect in its absorption, such as pernicious anemia.

Vitamin B-12 supplements contain the active vitamin, as well as several analogs; the analogs have little or no vitamin activity. The presence of vitamin C, thiamine, and vitamin E in vitamin B-12 supplements may cause the creation of undesirable analogs, which can interfere with normal vitamin function.

Commercially produced vitamin B-12 is still commonly produced in the form of cyanocobalamin, which is produced by bacterial fermentation, and is the cheaper, less bioavailable version. Most vitamin suppliers use the cheaper version knowing that few consumers read the label closely, only looking for the term "Vitamin B12", and not really understanding the difference.  However, if given the choice, wise consumers have learned to look for "methylcobalamin" on the label, understanding that it is far more absorbable, realizing greater benefits.
 

Consequence of Deficiency

If normal vitamin B-12 levels of 100 to 1,000 micrograms per milliliter fall to below 100 micrograms, pernicious anemia occurs. Pernicious anemia can result from an inadequate dietary intake of the vitamin; a diminished secretion of intrinsic factor by the glands of the stomach; the partial or complete removal of the stomach; or from a lack of the transport proteins transcobalamin I and II.

An additional cause of vitamin B-12 deficiency is the atrophy of the mucosal cells lining the stomach. This atrophy can result from genetic facts, alcoholism, iron deficiency, or thyroid gland disorders. An infection with the intestinal parasite Diphyllobothrium latum can produce pernicious anemia; the worm absorbs the available vitamin B-12, leaving little or none for the host's use. In the latter case, the anemia is easily cured by expulsion of the worm from the intestines.

Injections of vitamin B-12 can control pernicious anemia; however, the anemia must be detected at an early stage so that treatment starts prior to irreversible nerve degeneration. It is possible to diagnose vitamin B-12 deficiency on the basis of blood levels of the vitamin using microbiological techniques.

Since the body is efficient in storing vitamin B-12, it could take up to six years before vitamin B-12 deficiency symptoms develop in a diet devoid of the vitamin. Children of vegetarian parents can become vitamin B-12 deficient in two to three years, as they have no vitamin B-12 stores in their bodies.
 

Toxicity Factors

Vitamin B-12 is nontoxic to humans in doses exceeding the RDA by 10,000 times. Water-soluble vitamins in excess tend to be excreted in the urine, rather than stored in the tissues as are fat-soluble vitamins.
 

Recommended Dietary Allowance

 

age	RDA (mcg)	RNI (mcg)
infants/children
0-6 months	0.3	0.3
6-12 months	0.5	0.4
1-3 years	0.7	0.5
4-6 years	1.0	0.8
7-10 years	1.4	1.0
males
11-14 years	2.0	1.2
15+	2.0	1.5
females
11-14 years	2.0	1.2
15+	2.0	1.5
pregnancy	2.2	-
lactation	2.6	2.0

The amount of dietary vitamin B-12 needed for normal human metabolism appears to be very small. Reported minimum requirements have been from 0.6 to 1.2 mmicrograms per day, with a range to approcimately 2.8 micrograms to allow for individual variance. The ordinary diet easily provides this amount. For exammple, one cup of milk, one egg, and four ounces of meat provide 2.4 micrograms. The Recommended Daily Allownce standards recommends a daily intake of 3.0 micrograms for adults.

For over thirty years, Recommended Daily Amounts has existed in the United Kingdom. It has been used to measure the adequacy of an individual's diet. However, in 1991 the Committee on Medical Aspects of Food Policy (COMA) gave forth a whole new set of figures upon the request of the Department of Health's Chief Medical Officer. Reference Nutrient Intake (RNI) is one of these sets collectively known as "Dietary Reference Values." RNI is an amount of a nutrient that is enough for almost every individuals, even someone who has high needs for the nutrient. This level of intake is, therefore, considerably higher than what most people would need. If individuals are consuming the RNI of a nutrient they are most unlikely to be deficient in that nutrient.

Food Sources

Low: (0.5 - 5 mg/100 g)
 

Beef	Cheese
Chicken	Cod
Egg	Flounder
Haddock	Halibut
Lamb	Lobster
Milk	Pork
Scallop	Shrimp
Swordfish	Tuna
Whale

Medium: (5 - 50 mg/100 g)
 

Beef heart	Chicken heart
Chicken liver	Clams
Crab	Egg yolk
Frankfurters	Herring
Oysters	Rabbit kidney
Rabbit liver	Rabbit heart
Salmon	Sardines

High: (50 - 500 mg/100 g)
 

Beef brain	Beef kidney
Beef liver	Lamb kidney
Lamb liver	Pork liver
Veal liver

 

Abstracts

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