What is vitamin B12? What is Cobalamin?

What is vitamin B12? What is Cobalamin?


MNT Knowledge CenterVitamin B12, also known as Cobalamin is one of the eight B vitamins. It is a water soluble vitamin, meaning it dissolves in water and travels through the bloodstream. The human body does not store cobalamin – any excess or unwanted amounts are excreted through urine.

Cobalamin plays a vital role in normal brain and nervous system functioning, as well as the formation of red blood cells.

Experts say vitamin B12 plays a role in the metabolism of every cell in our bodies. It especially affects DNA regulation and synthesis, as well as the synthesis of fatty acids and energy production.

Vitamin B12 is structurally the most complicated vitamin, it is also the largest. Cobalamin can only be industrially produced through bacterial fermentation synthesis.

Those with B12 deficiency have a serious risk of permanent nerve and brain damage. Individuals with Crohn’s disease involving the small intestine, as well as those who have undergone small intestine resection may not be able to absorb cobalamin properly and may experience deficiency.

Vegans, those who consume no animal sourced food products at all, have a considerably higher risk of developing vitamin B12 deficiency, especially during pregnancy and lactation. Plant sourced foods do not have enough cobalamin to guarantee long-term human health (See paragraph for vegans further down this page).

According to Medilexicon’s medical dictionary:

Cobalamin is a “General term for compounds containing the dimethylbenzimidazolylcobamide nucleus of vitamin B12.”

Vitamin B12 is a “generic descriptor for compounds exhibiting the biologic activity of cyanocobalamin; the antianemia factor of liver extract that contains cobalt, a cyano group, and corrin in a cobamide structure. Several substances with similar formulas and with the characteristic hematinic action have been isolated and designated: B12a, hydroxocobalamin; B12b, aquacobalamin; B12c, nitritocobalamin; B12r, cob(II)alamin; B12s, cob(I)alamin; B12III, factors A and V1a (cobyric acid) and pseudovitamin B12. Vitamins B12a and B12b are known to be tautomeric compounds; B12b has been obtained from cultures of Streptomyces aureofaciens; B12c has been obtained from cultures of Streptomyces griseus and is distinguishable from B12 by differences in its absorption spectrum. The physiologically active vitamin B12 coenzymes are methylcobalamin and deoxyadenosinecobalamin. A deficiency of vitamin B12 is often associated with certain methylmalonic acidurias.”

A research team from Japan and Italy wrote in the Journal of Agricultural Food Chemistry that vegetarians and vegans are more likely to develop vitamin B12 deficiency. The human body is unable to use the plant-based form of the vitamin, they explained.

Vitamin B12 deficiency

Vitamin B12 deficiency can result in irreversible and potentially severe damage, especially to the human nervous system and brain. Even at slightly lower-than-normal B12 levels, a person can experience depression, memory problems and tiredness. However, these symptoms are not specific enough to diagnose vitamin B12 deficiency.

Some people who do not get enough vitamin B12 have a higher risk of developing psychosis, mania, or pernicious anemia.

Pernicious anemia – also known as Addison’s anemia, addisonian anemia, and Biermer’s anemia, is a blood disorder. Patients do not have enough IF (intrinsic factor), a protein substance in the stomach that allows the body to absorb vitamin B12. Treatment involves administering vitamin B12 injections. It has to be injected because pernicious anemia patients do not have an effective form of IF, and thus do not absorb orally administrated vitamin B12 properly.

Signs and symptoms of pernicious anemia include:

  • Fatigue
  • Dizziness, especially when standing up from a seated or lying position
  • Shortness of breath
  • Headache
  • Cold hands and/or feet
  • Chest pain
  • Pale skin
  • Pale gums
  • Arrhythmias
  • Heart murmur
  • Enlarged heart
  • Long-term risk of heart failure.

As mentioned earlier in this text, strict vegetarians (vegans) risk developing vitamin B12 deficiency if they do not take supplements (See paragraph for vegans further down this page).

Signs and symptoms of vitamin B12 deficiency include:

    Nervous system symptoms

  • Tingling in hands and feet
  • Numbness in hands and feet
  • Loss of reflexes
  • Muscle weakness
  • Balance problems which may affect standing still or walking
  • Confusion (severe deficiency)
  • Dementia (severe deficiency)
  • Depression (more common in severe deficiency)
  • Memory loss (severe deficiency).
  • Digestive tract symptoms

  • Nausea
  • Vomiting
  • Abdominal bloating
  • Abdominal gas
  • Diarrhea
  • Constipation
  • Loss of appetite
  • Weight loss.
  • Other symptoms

  • Enlarged liver
  • A beefy, red, smooth tongue
  • Inflants may have unusual movements (e.g. face tremors), reflex problems, feeding difficulties, irritation, and eventual growth problems if left untreated.

Good food sources of vitamin B12

Vitamin B12 can be found naturally in animal products, such as fish, meat, poultry, eggs, etc. It is not typically found in naturally presented plant foods, but exists in fortified cereals. Some nutritional yeast products may contain vitamin B12.

The following foods are known to be good sources of vitamin B12

  • Beef, pork, lamb
  • Fish
  • Yogurt
  • Haddock
  • Tuna
  • Milk
  • Cheese
  • Some nutritional yeast products
  • Ham
  • Eggs
  • Poultry.

Vegans – people who consume no animal sourced proteins at all should take vitamin B12 dietary supplements to avoid deficiency. Supplements are usually presented as cyanocobalamin, which the human body easily converts to the active forms of methylcobalamin and 5-deoxyadenosylcobalamin. Some dietary supplements may also contain methylcobalamin and other forms of vitamin B12.

According to experts, there is no evidence which suggests any of the forms differ in absorption or bioavailability. However, our ability to absorb this vitamin from dietary supplements is mainly limited by the capacity of intrinsic factor. In healthy people, for example, only approximately 10mcg of a 500mcg oral supplement is actually absorbed by the body.

Pregnant and lactating strict vegans need to make sure their vitamin B12 is adequate.

The majority of children and adults in North America and Europe ingest adequate amounts of vitamin B12. Some individuals, such as seniors, patients with pernicious anemia, and those with achlorhydria or intestinal disorders may have problems absorbing vitamin B12 from food properly, and even oral supplements. Consequently, US authorities estimate that between 1.5% and 15% of the general American population may be affected by some level of vitamin B12 deficiency.

The Framingham Offspring Study indicated that vitamin B12 prevalence in the USA may be higher than experts had previously assumed.

How much vitamin B12 should I consume?

The Institute of Medicine, USA has the following recommended daily intakes (RDAs) for vitamin B12:

  • Infants 0 to 6 months 0.4 mcg
  • Infants 7 to12 months 0.5 mcg
  • Babies/toddlers 1 to 3 years 0.9 mcg
  • Children 4-8 years 1.2 mcg
  • Children 9 to 13 years 1.8 mcg
  • Teens and adults14+ years 2.4 mcg
  • Pregnant mothers 2.6 mcg
  • Lactating (breastfeeding) mothers 2.8 mcg.

Further reading:
What Is Vitamin B12 Deficiency? What Causes Vitamin B12 Deficiency?

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