1.5.4.h. Vitamin B12 (Cobalamin)

Cobalamins

What is the general name for the group of vitamin B₁₂ compounds that contain cobalt?

Cyanocobalamin

Which form of vitamin B₁₂ is considered the most biologically active in the text?

Cyanocobalamin, hydroxocobalamin, and nitrosocobalamin

What are the principal forms of cobalamin mentioned in the text?

It contains the mineral cobalt as part of its chemical structure.

Why is vitamin B₁₂ called cobalamin?

Antipernicious anemia factor, erythrocyte maturation factor (EMF), and animal protein factor

What older names were used for vitamin B₁₂?

It functions in methyl-group transfer (methylation) reactions.

What is the major metabolic role of vitamin B₁₂ in protein metabolism?

Folate (folic acid)

Vitamin B₁₂ works closely with which vitamin in one-carbon and methyl-group metabolism?

Normal erythrocyte maturation and red blood cell formation

What blood-forming process depends on vitamin B₁₂?

Heme and nucleic acids (DNA)

Vitamin B₁₂ contributes to the synthesis of which major cellular compounds?

It is required for normal nerve function and maintenance of neurologic integrity.

Why is vitamin B₁₂ important to the nervous system?

Nervous system, bone marrow, and gastrointestinal tract

Which body systems or tissues particularly depend on vitamin B₁₂ for normal function?

It supports normal growth and development.

What general developmental role does vitamin B₁₂ have?

No. Folate may improve the anemia, but it does not correct the neurologic damage of vitamin B₁₂ deficiency.

Can folic acid alone correct all manifestations of vitamin B₁₂ deficiency?

No. Vitamin B₁₂ cannot replace folate when folate itself is deficient.

Can vitamin B₁₂ substitute for folic acid in folate-deficiency conditions such as sprue?

Both can cause megaloblastic anemia, but vitamin B₁₂ deficiency can additionally cause irreversible neurologic injury if left untreated.

Why is it important to distinguish vitamin B₁₂ deficiency from folate deficiency before treatment?

Terminal ileum

Where is vitamin B₁₂ primarily absorbed?

Intrinsic factor (IF)

What gastric substance is required for normal vitamin B₁₂ absorption?

By parietal cells of the stomach

Where is intrinsic factor produced?

It binds vitamin B₁₂ and allows the B₁₂–intrinsic factor complex to be absorbed in the ileum.

What is the role of intrinsic factor in vitamin B₁₂ absorption?

Vitamin B₁₂

Which B vitamin can be stored in substantial amounts for several years?

Liver

What is the major storage site of vitamin B₁₂?

The body has large hepatic stores that can last for several years.

Why may vitamin B₁₂ deficiency take years to appear after intake or absorption becomes inadequate?

Kidneys, brain, spleen, pancreas, bone marrow, muscles, and testes

Besides the liver, which tissues contain relatively high concentrations of vitamin B₁₂?

Yes, but this synthesis is not nutritionally significant in humans.

Can intestinal bacteria synthesize vitamin B₁₂?

Pernicious anemia

What classic disease is associated with vitamin B₁₂ deficiency caused by impaired intrinsic factor–dependent absorption?

Megaloblastic macrocytic anemia

What type of anemia is classically produced by vitamin B₁₂ deficiency?

They become abnormally large and fail to mature normally, reducing effective RBC production.

What happens to red blood cells in vitamin B₁₂ deficiency?

Anorexia, vomiting, diarrhea, achlorhydria, abdominal pain, and weight loss

What gastrointestinal symptoms may occur in vitamin B₁₂ deficiency?

Paresthesia, loss of vibration sense, spinal cord degeneration, and difficulty walking

What neurologic manifestations may occur in advanced vitamin B₁₂ deficiency?

Yellowish skin and enlargement of the liver and spleen

What skin or organ changes may accompany severe vitamin B₁₂ deficiency according to the text?

Paresthesia, or tingling of the limbs.

What sensory symptom may be an early clue to neurologic involvement in vitamin B₁₂ deficiency?

Walking becomes difficult because of neurologic impairment.

What happens to gait in advanced vitamin B₁₂ deficiency?

Failure of vitamin B₁₂ absorption due to intrinsic factor deficiency, usually from autoimmune loss of gastric parietal-cell function.

What is the fundamental problem in classic pernicious anemia?

Macrocytic megaloblastic anemia

Pernicious anemia belongs to which morphologic type of anemia?

2.4 µg/day

What Philippine RNI for vitamin B₁₂ is listed for males and females 10 years and older?

+0.2 µg/day

How much additional vitamin B₁₂ is listed for pregnancy?

+0.4 µg/day

How much additional vitamin B₁₂ is listed for lactation?

Animal-derived foods

What type of foods naturally provide significant amounts of vitamin B₁₂?

Unfortified plant foods

Which food group contains little to essentially no naturally occurring vitamin B₁₂?

Liver

Which food is especially concentrated in vitamin B₁₂?

Milk, yogurt, eggs, sardines, and other animal foods

What common foods listed in the text are good sources of vitamin B₁₂?

Strict vegan diet

Which dietary pattern places a person at increased risk for vitamin B₁₂ deficiency if no fortified foods or supplements are used?