Vitamin B12 is generally present as cyanocobalamin in various dietary supplements. Cyanocobalamin is the inactive form which readily and easily gets converted into more usable forms like methylcobalamin and 5-deoxyadenosylcobalamin. methylcobalamin and other forms of vitamin B12 supplements can also be contained in dietary supplements.
In terms of bioavailability, established evidence does not suggest distinction among the varied forms. Also, no major difference is observed with respect to absorption. But the capacity of the intrinsic factor is a limiting factor to the ability of the body to absorb vitamin B12 from dietary supplements. For example, of a 500 microgram of oral supplement, a mere 10 mcg is absorbed by the body of normal healthy people.
It is also available in various sublingual preparations. Thus its presence is not limited to oral dietary supplements only. Various tablets and lozenges can be made to be prepared in order to contain this vital vitamin. Although evidence does not distinguish between the efficiency of oral and sublingual forms, frequent marketing of such preparations often seem to stress on their superior bioavailability.
We may come across vitamin B12 acting as a supplement in processed food items. It is also not uncommon to find it in the form of vitamin pills, including multivitamins. Supplementation of this vitamin in healthy subjects by liquid, transdermal patch, nasal spray, or injection is widespread. The vitamin is available in isolation or in combination with various other important supplements. B12 is one of the ingredients in energy drinks and shots.
In spite of various designs such as lozenges, pills,and lollipops for the purpose of sublingual absorption , the sublingual route (in which the tongue most directly absorbs the vitamin B12) has not proven to be helpful. Various studies and experiments have backed this result. It is not the placement of the tablet but the high dosages that cause sublingual methods of replacement to be effective. These high doses are extremely useful as treatments.
Sometimes digestive absorption is ineffective. In such cases, injection and patches are used. However, modern high potency oral supplements make this course of action unnecessary. Oral route can be used to treat even pericious anemia. The massively large doses carried by these supplements is absorbed by the intestinal regions by the process of passive diffusion. However, treatment with intravenous, transdermal or intramuscular hydroxocobalamin. Vitamin B12 is essential if the patient is characterised by innate problems in the methyltransfer pathway.
Diverting attention to some of the non-cyano forms as suppplements, the following can be noticed. Recently, 1 mg tablets have come out in the markets for sublingual methylcobalamin. These tablets are beneficial in a number of ways. They are seen to have higher bioavailability as compared to the older cyanocobalamin. Methylcobalamin have no side effects in the form of release of cyanide, even thought the amount of cyanide excreted is a very small amount as compared to those absorbed from many natural food items. It is usually seen to be 2% of the weight or about 20 micrograms in a 1 mg cyanocobalamin tablet. There have been no questions raised so far over either the safety of cyanocobalamin or of the other types.