Micronutrients

Question 1

Causes of micronutrient deficiency

Answer 1

Poor dietary intake 
Excessive energy dense/nutrient light diets
Extreme diets (removal of one or more food groups)

Question 2

Vit C absorbed at

Answer 2

SI, Stomach and Buccal mucosa

Question 3

Vit C mechanism of absorption

Answer 3

Buccal - passive diffusion
GI rapid if mucosal conc < 6mmol/L
20mg - 98%
100mg - 6%

Scurvy

Question 4

B1 absorbed at

Answer 4

jejunum and ileum

Question 5

B1 mechanism of absorption

Answer 5

Low conc - Na dependent process 
High conc (>8mg single dose) passive diffusion

Question 6

B2 absorbed at

Answer 6

Small intestine

Question 7

B2 mechanism of absorption

Answer 7

2 stages from proteins - proteolytic enzymes and hydrolyses (brush border enzymes)

Question 8

B12 absorbed at

Answer 8

Ileum - distal portion

Question 9

B12 mechanism of absorption

Answer 9

Pepsin and HCL from proteins
B12 binds transcorrin - secretions
Jejunum: B12 released and binds intrinsic factor from stomach
Pernicious anaemia

Question 10

Vit A absorbed at

Answer 10

Small intestine - duodenum and ileum

Carotenes

Question 11

Vit A mechanism of absorption

Answer 11

Protein-retinol complex hydrolyses (pepsin) in SI and absorbed

Carotenes solubilised into micelle by passive diffusion through membrane -> convert to retinol

Question 12

Vit D absorbed at

Answer 12

Small intestine

Question 13

Vit D mechanism of absorption

Answer 13

Mixed micelle by passive diffusion into intestinal mucosal cell
Liver 25-hydroxylase enzyme convert D2 and D3 to main circulating form of 25 hydroxy-bit D

Question 14

Vit D deficiency risk factors

Answer 14

Pigmented skin (non-white ethnicity)
 Lack of sunlight exposure
 Skin concealing garments or strict sunscreen use
 Multiple, short interval pregnancies
 Elderly or housebound
 Vegan / vegetarian or high phytate consumption such as in chapatis
 Malabsorption (e.g., inflammatory bowel disease, coeliac disease, pancreatic
insufficiency)
 Use of anticonvulsants, rifampicin, cholestyramine, anti-retrovirals

Question 15

Calcium absorption site

Answer 15

Primarily duodenum

jejunum

Question 16

Iron absorption site

Answer 16

Primarily proximal small intestine