B12 and Folate

Question 1

How is B12 absorbed from the diet and taken to the bone marrow?

Answer 1

In the stomach it binds to the glycoprotein intrinsic factor (IF)

The IF-B12 complex binds to the ileum and the B12 is absorbed

B12 binds to transcoblamin in the portal blood and is delivered to the bone marrow and other tissues

Question 2

What can a B12 deficiency result from?

Answer 2

• dietary deficiency…vegan/poor
• lack of IF = pernicious anaemia (parietal cells don’t produce enough) / gastrectomy
• IF-B12 complex binding to ileum is affected: disease of terminal ileum- crohn’s/ileal resection/tropical sprue
• transcobalamin congenital deficiency

Question 3

Where is folate absorbed?

Answer 3

In the duodenum and jejunum

Question 4

How is folate absorbed and transported around the body?

Answer 4

Absorped in the duodenum and jejunum and then converted into methylTHF which circulates in the plasma

Question 5

How can folate deficiencies occur?

Answer 5

Dietary deficiency
Proximal small bowel disease eg coeliac disease
Crohn’s disease drugs which inhibit necessary enzymes (dihydrofolate reductase)
Alcoholism
Urinary loss of folate in liver disease and heart failure

Question 6

When would there be an increased use of folate?

Answer 6

During pregnancy
Increased erythropoiesis eg haemolytic anaemia
Severe skin diseases ie psoriasis, exfoliative dermatitis

Question 7

What does pancytopenia mean?

Answer 7

Low platelets and neutrophil counts

Question 8

What are the neurological effects of a vitamin B12 deficiency?

Answer 8

Neurological disease: you get focal demyelination affecting the spinal cord, peripheral nerves and optic nerves (problems with vision)

Depression and Dementia can also develop