Vitamin B-12 (Cobalamine)

Question 1

B-12 food sources

Answer 1

• animal products only
• meat
• poultry
• fish
• shellfish*best source
• eggs
• milk

Question 2

B-12 digestion

Answer 2

• attached to polypeptides in foods
• released by actin of gastric acid and pepsin
• interacts with:
• R-protein(in saliva/gastric juice)
• Intrinsic Factor (in parietal cell in stomach)

Question 3

B-12 absorption

Answer 3

-R-protein in salvary glands-intrinsic factor released 
to 
trypsin 
to 
pancreas 
to 
absorbed in the blood stream and then recycled back into the body 
-medication- passive(used if IF is not produced)
-malabsorption:
--achlorydria 
--low gastric acid secretion 
--lack of IF
--insufficient pancreas

Question 4

B-12 functions

Answer 4

1. methylcobalamine- required for methionine synthesis from Hcy
2. adenosylcobalmin-required for propinyl CoA oxidation pathway to succinyl CoA
   - -elevated in blood/urine with methylmalcinic acid (MMA)=indicator of B-12 deficiency
3. nerve functions- maintains myelin sheath-messages carried through conductivity

Question 5

B-12 deficiency

Answer 5

methylmalonyl CoA to succinyl CoA

homocysteine and folic acid to methionine

Question 6

B-12 RDA

Answer 6

in 1998=2.4 ug/d

No UL

Question 7

B-12 toxicity

Answer 7

none reported

• CVD risk= increase HCY
• megaloblastic anemia= decrease in DNA synthesis
• neuropathy=defective mylination

Question 8

B-12 symptoms

Answer 8

-fatigue, short of breath
-palputation*
-numbness
-muscle weakness
-staggering
-sore mouth
-headache
-confusion, forgetfulness*
insomnia*

Question 9

population at risk for B-12 deficiency

Answer 9

• vegans and their breast fed infants
• elderly- atrophic gastritis
• long-term use of antacids
• alcoholics

Question 10

B-12 nutrition assessment

Answer 10

• serum B-12/histology
• maintenance of heme
• MMA=good indicator
• Hcy=not good
• Schiling Test= most accurate
• -measures urine output