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Vitamin B12

What is vitamin B12?

Vitamin B12, also known as cobalamin, is a water soluble vitamin containing cobalt in its structure. Like folic acid, vitamin B12 deficiency also causes anemia. It is an essential micronutrient found in several foods such as meat, fish, and dairy products. B12 is an essential vitamin that controls nerve tissue, brain function, and red blood cell production.

Vitamin B12 also known as cobalamin structure with deficiency, natural food sources, functions

It is the first natural product that contains cobalt atom in its structure. The elemental analysis gives the various structures of vitamin B12 but the structure which is now accepted requires a formula of C63H88CoN14O14P.

Vitamin B12 structure

It has been obtained as a red crystalline solid that dissolves in water to give red solutions. It is a coordination complex of cobalt. The cobalt atom in vitamin B12 is placed on the center of a corrin ligand which is further bound by a benzimidazole ligand and adenosyl group given above the picture.

The different values of molecular weight are obtained by the ebullioscopic and X-ray methods. Therefore, vitamin B12 is the collection of chemical compounds which are different molecular weights. All these chemical compounds are similar structures and show vitamin activity in the biological system.

  • In cyanocobalamin, the adenosyl ligand is replaced by the cyanide group.
  • In hydroxocobalamin, the adenosyl ligand is replaced by the hydroxide group.
  • In methylcobalamin, the adenosyl ligand is replaced by the methyl group.

The hydrolysis of vitamin B12 or cyanocobalamin with hydrochloric acid under different conditions produces ammonia, 1-aminopropyl-2-ol, 5,6-dimethylbenzimidazole, 5,6-dimethylbenzimidazole-1-α-D-ribofuranoside, and 3-phosphate of 5,6-dimethylbenzimidazole-1-α-D-ribofuranoside.

Source of vitamin B12

Like other B vitamins, it is an essential nutrient that cannot be produced in our bodies. Therefore, we need to get vitamin B12 from external sources like diet or supplements. The animal products such as meat and dairy products are the main sources of vitamin B12.

Like folic acid, the deficiency also causes anemia. It can be easily treated by supplements or food sources that contain high levels of vitamin B12. The food sources which contain a huge amount of B12 are,

  • Beef, liver, and chicken
  • Fish and shellfish like trout, salmon, tuna fish, and clams
  • Milk and dairy products like yogurt, and cheese
  • Eggs
  • Fortified cereal
  • Fortified nutritional yeast


Most people in the United States and other well-developed counties get enough B12 in their daily nutrients. Vitamin B12 deficiency can occur in two ways,

  • When people do not get enough B12 in their daily nutrients.
  • When our body does not absorb or store this nutrient.

The most common symptoms shown due to B12 deficiency are,

  • Feeling tired and weak causes difficulty walking.
  • Mania and psychosis cause depression
  • Poor memory, poor reflexes, and confusion.
  • Breathlessness.
  • Headaches.
  • Pale skin.

It is an important B vitamin that serves a crucial role in nerve tissue health, brain function, and the production of red blood cells.

It is an essential nutrient for healthy blood. The deficiency of vitamin B12 leads to decreased normal red blood cells or causes iron deficiency anemia. Megaloblastic anemia or nutritional deficiency anemia is also caused by the deficiency of B12 or folate which affects our blood oxygen levels.

Functions of vitamin B12

Vitamin B12 functions or control several biological processes in our body. The main functions of B12 are,

  • It functions on red blood cell production to prevent anemia.
  • It functions on the brain and nervous system of our body to increase cognition or thinking power.
  • It helps to create or regulate deoxyribonucleic acid (DNA).
  • It helps to protect our eyes from macular degeneration.
  • Like other vitamins, vitamin B12 is also useful for energy production in biological systems.

Intake requirements

  • According to the National Institutes of Health (NIH), vitamin B12 for women and men ages 14 and up is 2.4 micrograms (mcg) per day.
  • For pregnant or breastfeeding women the daily requirement of B12 increases. Therefore, pregnant women should need 2.6 mcg per day during pregnancy, and for breastfeeding women, it should be 2.8 mcg per day.
  • Excessive intake of B12 does not cause any toxic or harmful effects on our bodies.

Older peoples have a high risk for deficiency of B12 because they are unable to absorb B12 from naturally occurring foods.  A high risk of vitamin B12 deficiency for vegetarians comes due to their diet excluding food products that come from animal sources.