Food High In Vitamin B 12
Vitamin B12 , also called cobalamin , is a water soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins. It is normally involved in the metabolism of every cell of the body, especially affecting DNA synthesis and regulation, but also fatty acid synthesis and energy production.
Vitamin B12 is a class of chemically-related compounds, all of which have vitamin activity. It is structurally the most complicated vitamin and it contains the biochemically rare element cobalt. Biosynthesis of the basic structure of the vitamin can only be accomplished by bacteria, but conversion between different forms of the vitamin can be accomplished in the human body. A common synthetic form of the vitamin, cyanocobalamin, does not occur in nature, but is used in many pharmaceuticals and supplements, and as a food additive, due to its stability and lower cost. In the body it is converted to the physiological forms, methylcobalamin and adenosylcobalamin, leaving behind the cyanide, albeit in minimal concentration. More recently, hydroxocobalamin (a form produced by bacteria), methylcobalamin, and adenosylcobalamin can also be found in more expensive pharmacological products and food supplements. The utility of these is presently debated.
Historically, vitamin B12 was discovered from its relationship to the disease pernicious anemia, which is an autoimmune disease that destroys parietal cells in the stomach that secrete intrinsic factor. Intrinsic factor is crucial for the normal absorption of B12, so a lack of intrinsic factor, as seen in pernicious anemia, causes a vitamin B12 deficiency. Many other subtler kinds of vitamin B12 deficiency, and their biochemical effects, have since been elucidated.
Terminology
The name vitamin B12 , known as vitamin B (commonly B or B12 for short) or also cyanocobalamin generally refers to all forms of the vitamin. Some medical practitioners have suggested that its use be split into two different categories, however.
- In a broad sense B12 refers to a group of cobalt-containing vitamer compounds known as cobalamins: these include cyanocobalamin (an artifact formed as a result of the use of cyanide in the purification procedures), hydroxocobalamin (another medicinal form, produced by bacteria), and finally, the two naturally occurring cofactor forms of B12 in the human body: 5'-deoxyadenosylcobalamin (adenosylcobalamin—AdoB12), the cofactor of Methylmalonyl Coenzyme A mutase (MUT), and methylcobalamin (MeB12), the cofactor of 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR).
- The term B12 may be properly used to refer to cyanocobalamin, the principal B12 form used for foods and in nutritional supplements. This ordinarily creates no problem, except perhaps in rare cases of eye nerve damage, where the body is only marginally able to use this form due to high cyanide levels in the blood due to cigarette smoking, and thus requires cessation of smoking, or else B12 given in another form, for the optic symptoms to abate. However, tobacco amblyopia is a rare enough condition that debate continues about whether or not it represents a peculiar B12 deficiency which is resistant to treatment with cyanocobalamin.
Finally, so-called Pseudo-B12 refers to B12-like substances which are found in certain organisms, including Spirulina (a cyanobacterium) and some algae. These substances are active in tests of B12 activity by highly sensitive antibody-binding serum assay tests, which measure levels of B12 and B12-like compounds in blood. However, these substances do not have B12 biological activity for humans, a fact which may pose a danger to vegans and others on limited diets who do not ingest B12 producing bacteria, but who nevertheless may show normal "B12" levels in the standard immunoassay which has become the normal medical method for testing for B12 deficiency.
Structure
Vitamin B12 is a collection of cobalt and corrin ring molecules which are defined by their particular vitamin function in the body. All of the substrate cobalt-corrin molecules from which B12 is made must be synthesized by bacteria. However, after this synthesis is complete, the body has a limited power to convert any form of B12 to another, by means of enzymatically removing certain prosthetic chemical groups from the cobalt atom. The various forms (vitamers) of B12 are all deeply red colored, due to the color of the cobalt-corrin complex.
Cyanocobalamin is one such "vitamer" in this B complex, because it can be metabolized in the body to an active co-enzyme form. However, the cyanocobalamin form of B12 does not occur in nature normally, but is a byproduct of the fact that other forms of B12 are avid binders of cyanide (-CN) which they pick up in the process of activated charcoal purification of the vitamin after it is made by bacteria in the commercial process. Since the cyanocobalamin form of B12 is easy to crystallize and is not sensitive to air-oxidation, it is typically used as a form of B12 for food additives and in many common multivitamins. However, this form is not perfectly synonymous with B12, inasmuch as a number of substances (vitamers) have B12 vitamin activity and can properly be labeled vitamin B12, and cyanocobalamin is but one of them. (Thus, all cyanocobalamin is vitamin B12, but not all vitamin B12 is cyanocobalamin).
Hydroxocobalamin is another form of B12 commonly encountered in pharmacology, but which is not normally present in the human body. Hydroxocobalamin is sometimes denonoted B 12a . This form of B12 is the form produced by bacteria, and is what is converted to cyanocobalmin in the commercial charcoal filtration step of production. Hydroxocobalamin has an avid affinity for cyanide ion and has been used as an antedote to cyanide poisoning. It is supplied typically in water solution for injection. Hydroxocobalamin is thought to be converted to the active enzymic forms of B12 more easily than cyanocobalamin, and since it is little more expensive than cyanocobalamin, and has longer retention times in the body, has been used for vitamin replacement in situations where added reassurance of activity is desired. Intramuscular administration of hydroxocobalamin is also the preferred treatment for pediatric patients with intrinsic cobalamin metabolic diseases, for vitamin B12 deficient patients with tobacco amblyopia (which is thought to perhaps have a component of cyanide poisoning from cyanide in cigarette smoke); and for treatment of patients with pernicious anemia who have optic neuropathy.
B12 is the most chemically complex of all the vitamins. The structure of B12 is based on a corrin ring, which is similar to the porphyrin ring found in heme, chlorophyll, and cytochrome. The central metal ion is cobalt. Four of the six coordination sites are provided by the corrin ring, and a fifth by a dimethylbenzimidazole group. The sixth coordination site, the center of reactivity, is variable, being a cyano group (-CN), a hydroxyl group (-OH), a methyl group (-CH 3 ) or a 5'-deoxyadenosyl group (here the C5' atom of the deoxyribose forms the covalent bond with Co), respectively, to yield the four B12 forms mentioned above. Historically, the covalent C-Co bond is one of first examples of carbon-metal bonds to be discovered in biology. The hydrogenases and, by necessity, enzymes associated with cobalt utilization, involve metal-carbon bonds.
Synthesis
Vitamin B12 cannot be made by plants or animals. Only bacteria have the enzymes required for its synthesis. The total synthesis of B12 was reported by Robert Burns Woodward and Albert Eschenmoser, and remains one of the classic feats of organic synthesis.
Species from the following genera are known to synthesize B12: Aerobacter , Agrobacterium , Alcaligenes , Azotobacter , Bacillus , Clostridium , Corynebacterium , Flavobacterium , Micromonospora , Mycobacterium , Nocardia , Propionibacterium , Protaminobacter , Proteus , Pseudomonas , Rhizobium , Salmonella , Serratia , Streptomyces , Streptococcus and Xanthomonas . Industrial production of B12 is through fermentation of selected microorganisms. Streptomyces griseus , a bacterium once thought to be a yeast, was the commercial source of vitamin B12 for many years. The species Pseudomonas denitrificans and Propionibacterium shermanii are more commonly used today. These are frequently grown under special conditions to enhance yield, and at least one company, Rhône-Poulenc of France, at one point used genetically engineered versions of one or both of these species. It is not clear whether Sanofi-Aventis, the company which the pharmaceutical division of Rhône-Poulenc merged into, has continued the use of genetically modified organisms.
Functions
Vitamin B 12 is normally involved in the metabolism of every cell of the body, especially affecting the DNA synthesis and regulation but also fatty acid synthesis and energy production. However, many (though not all) of the effects of functions of B12 can be replaced by sufficient quantities of folic acid (another B vitamin), since B12 is used to regenerate folate in the body. Most vitamin B 1
Vitamin B 12 - High Performance Fitness
High Potency Vitamin B-12 Supplement. Vitamin B-12, the energy ... percent of older adults are B-12 deficient, most often related to an inability to absorb vitamin B-12 found in food.*
Vitamin B12 - Wikipedia, the free encyclopedia
The name vitamin B12, known as vitamin B 12 (commonly B ... Therefore, absorption of food vitamin B12 requires an ... supplements carry such large doses of the vitamin that 1% to 5% of high ...
What foods are naturally rich in vitamin B12?|B12 Patch ...
Even if you are using supplementation like the vitamin B-12 patch, it's still important to make sure you're eating foods that are high in vitamin B-12.
Food Standards Agency - Eat well, be well - Vitamin B12
... the food we eat; is needed to process folic acid; What happens if I take too much? There isn't enough evidence to know what the effects might be of taking high doses of vitamin B 12 ...
Vitamin B12 - The Linus Pauling Institute
In fact, high-dose oral therapy is considered to be as effective as intramuscular injection (7-10). Food-bound vitamin B 12 malabsorption. Food-bound vitamin B 12 malabsorption is ...
Top 10 Foods Highest in Vitamin B12
Vitamin B-12 is the largest and most complex vitamin currently known to man. A slight deficiency of vitamin B-12 can lead to anemia, fatigue, mania, and depression, while a long ...
Dietary Supplement Fact Sheet: Vitamin B12
Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods ... No effect of vitamin B-12 treatment on cognitive function and depression: a ...
Vitamin B-100 by NOW Foods
Vitamin B-100, 100 Caps High Potency B-Complex Regular Retail: $17.99 Our low price: $12.99 ... Vitamin B-50 Caps by NOW Foods, 100 Caps: Vitamin B-12 5000mcg by NOW Foods, With Folic Acid ...
Foods rich in Folic Acid and Vitamin B12
Foods rich in folic acid and vitamin B 12. Why are folic acid and vitamin B 12 so important ... Include more foods that are high in Folic Acid in the diet; Fruit and vegetables ...
Foods rich in Vitamin B12 high food sources
B12 Vitamin foods A big list of different common foods very high in vitamin B12. Highest B vitamin sources of food