B-12

Question 1

Food sources

Answer 1

animal products only

Question 2

Digestion/Absorption

Answer 2

Released from food matrix, attached to polypeptides in foods, released by action of gastric acids and pepsin, in duodenum

• Interactions with r proteins in saliva and gastric juices
• -intrinsic factor docking station on receptor for absorption of VB12

Question 3

Absorption

Answer 3

• Pharmacological Dose- passive diffusion, used for people not producing IF
• Malabsorption- older than 51/supplement needed,
• -achlorydia- low gastic acid secretion
• -lack of IF-used for those with anemia-deficient of IF
• • pancreatic insufficiency
• Decreased with increased intake

Question 4

Therapy

Answer 4

Many factors can disrupt this process
monthly injections of vit B12
Vit B 12 nasal get - effective form of therapy
Megadoses of vit B12 to allow to passive diffusion

Question 5

Functions

Answer 5

Methylcobalamin
Adenosylcobalamin
Nerve Functions

Question 6

Methlycobalamin

Answer 6

Coenzyme form of methionine synthesis

required for methionine synthesis from HCY

Question 7

Adenosylcobalmin

Answer 7

Coenzyme of methylmaloyl CoA mutase
-without enough of B12 L-methlymalonyl CoA will not transfer to succinyl CoA
-elevated in blood urine with methymalonia acid (MMA)
Nerve function
-maintains myelin sheath ( not sure the role)

Question 8

RDA

Answer 8

2.4 mcg/day NO UL

Question 9

Disease related to vB12

Answer 9

CVD risk, Megoblastic anemia, neuropathy

specific- confusion/forgetfulness, insomnia

Question 10

Population Risk

Answer 10

Vegan & their breastfed infants
elderly & atrophic gastritus
Long term use of acid reducing drugs
Alcoholics

Question 11

Nutritional Status

Answer 11

Serum b12
maintain hematological status 
methylmalony Acid [increase conc.] 
HCY- not a good source
Schilling test-most convient, absorption test- administer radioactive vB12--> measure urinary excretion