proactive health

[tommyturkey]

Is the absorption rate of a B12 tablet so small that one has to take 1000 micro grams in order to provide the RDA of 2-3 micrograms?

Is chewing a tablet and dissolving it under the tongue comparable to sublingual?

[nixmandy]

the thing about the tablet form is that tablets are not easily digested in the body. the did tests in NY awhile back and the studies show that the body does not usually break down vitamin tablets completely. They found tablets that had only partially been broken down before finding their way to the sewer system.
I think as long as your body can actually get in the nutrients that you will be fine. if you crunch it up then your body can get to and break down what is left of the tablet. It will probably tastes terrible but you will get the same affect as sublingual.

[Red_Star]

With intrinsic factor, 56% of a 1 mcg dose of vitamin B12 is absorbed.  However, if you exceed the capacity of intrinsic factor (between 1 and 2 mcg) the percentage of B12 absorbed is reduced.  Approximately 10 mcg of B12 is absorbed from a 500 mcg supplement.  

A small percentage (1 to 3%) of vitamin B12 intake is absorbed through passive diffusion without intrinsic factor.  In 2006, a study found that sufficiently high doses of oral B12 was as effective as intramuscular injection in treating vitamin B12 deficiency.  An older study, from 1998, concluded "In cobalamin deficiency, 2 mg of cyanocobalamin administered orally on a daily basis was as effective as 1 mg administered intramuscularly on a monthly basis and may be superior."

Almost any substance may be used sublingually if it dissolves easily in saliva.  However, factors that can affect absorption include oral pH, salivary enzymes, lipid solubility, and molecular weight (molecules may be too large to pass through the mucous membranes). A sublingual product, specifically created to ensure effective absorption, is recommended.