Vitamin B12 (Cobalamin)

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Vitamin B12 - Tulsa Nutritional Supplements - Functional MedicineIn contrast to the other water soluble vitamins, cobalamin is stored in the body (~4-5 mg).

There are 2 primary forms with which most people supplement: cyanocobalamin and methylcobalamin. Hydroxycobalamin is a stable form that is converted to the active, methylcobalamin form.

How it absorbs

When taken orally, Vitamin B12 binds to intrinsic factor which is produced in the stomach. The complex of Vitamin B12 & intrinsic factor is absorbable. Without intrinsic factor we cannot absorb Vitamin B12 through the gastrointestinal tract.

This issue is the most common reason that people don’t have adequate levels. We also commonly see deficiency in vegetarians and vegans because there are not good plant sources of B12.

Autoimmune attack of the gastric parietal cells destroys the bodies ability to produce intrinsic factor.

The B12-Intrinsic Factor complex is absorbed in the ileum of the small intestine. Some people may also have a gut disorder that could decrease the absorption of B12.

Good sources

This vitamin is not found in plants! It is synthesized only by microorganisms. Animals obtain cobalamin from intestinal flora or by eating the meats of other animals. Especially liver, whole milk, eggs, oysters, fresh shrimp, pork, and chicken.

DRI: 1.8-2.4 mg/d

Our sublingual methylcobalamin is 2.5mg per day and also contains 5-MTHF 1mg. We also give methylcobalamin as an injection and it is included in several of our IV nutritional formulas.


Vitamin B12 (cobalamin) is essential for 2 enzymatic reactions: synthesis of methionine and isomerization of methylmalonyl CoA that arises from odd fatty acid chains. Cobalamin converts some forms of TetraHydroFolate (THF) to the active form (5-MTHF). If cobalamin is deficient, the inactive forms build up and cannot be converted. Therefore, cobalamin deficiency can resemble folic acid deficiency and vice versa. This process is further discussed on the Methylation post.

Check out our podcast about methylation as well.

  • Cofactor in mitochondrial respiratory chain to produce energy via ATP
  • Cofactor in methionine synthase, an enzyme that methylates homocysteine to form methionine (see methylation post)
  • Cofactor in the synthesis of S-Adenosylmethionine (SAMe) which synthesizes neurotransmitters
  • Cofactor in the L-methylmalonyl-CoA mutase which synthesizes succinyl-CoA which metabolizes proteins and fats
  • Cofactor in folate metabolism (prevents folate derivatives from staying in non-bioactive form)
  • Cofactor in the metabolism of odd-chain fatty acids
  • Cofactor in the metabolism of branched chain amino acids (leucine, isoleucine, and valine)
  • Cofactor in the formation of red blood cells (RBCs) (succinyl-CoA is required for hemoglobin)
  • Cofactor in the formation of white blood cells (WBCs)
  • Modulates melatonin secretion via its role as a methyl donor, thus normalizing circadian rhythms
  • Key role in methylation and synthesis of DNA (low B12 causes hypomethylation of DNA)
  • Cofactor in donating methyl groups to myelin sheath around nerves (via SAMe)
  • Reduces neuropathic pain
  • Raises cysteine and glutathione (GSH) levels
  • Scavenges nitric oxide (NO); inhibits nitric oxide synthase
  • Repletion improves treatment response in depression
  • Inhibits proliferations of malignant cells in vivo
  • May enhance efficacy of methotrexate
  • Protects retinal neurons against N-methyl-D-aspartate receptor mediated glutamate neurotoxicity


Pernicious anemia. Deficiency is most often due to an inability to absorb the vitamin rather than an inadequate amount in the diet. Vitamin B12 deficiency can also lead to CNS symptoms. Folic acid supplementation can correct the anemia associated with vitamin B12 deficiency but not the CNS effects. Make sure you know which is deficient!

Deficiency causes excess methylmalonic acid which decreases fatty acid synthesis for nerve cells.

Toxicity: None known

I often look at methylcobalamin as a ‘litmus test’ of the quality of nutritional supplements. It is slightly more expensive to produce so it helps me to understand how important quality may be to the manufacturer. I only recommend methylcobalamin, adenosylcobalamin, or hydroxycobalamin supplementation whether it be orally or injectable. Most traditional doctors use the cyanocobalamin version in their ‘B12 injections.’

Cyanocobalamin has a cyanide molecule attached to it. Do you want to inject your body with cyanide?

We recommend a supplement with B12 (methycobalamin) in a sublinqual form. Sublinqual forms are absorbed directly into the blood system so we don’t have to worry about intrinsic factor and gut health for absorption.