micronutrients

Question 1

what are micronutrients

Answer 1

Vitamins, minerals and trace elements are fundamental groups of nutrients to sustain life
Physiological role at cellular level
Vitamins are organic molecules derived from plants, act as co-enzymes in metabolic pathways
Minerals and trace elements participate in a wide range of cellular mechanism

Question 2

what are vitamins

Answer 2

Require 13
4 fat soluble A D E K
9 water soluble – C and 8 B vitamins (thiamine B1, riboflavin B2, niacin B3, pantothenic B5, vitamin B6, folate B9 and vitamin B12)

Question 3

why is a balanced diet important

Answer 3

Range of micronutrients
Fortified to manage known population deficiencies
Processed foods tend to be nutrient light and energy dense

Question 4

what deficiencies are present in the UK

Answer 4

Generally well nourished
Concerns about marginalised groups, minority groups, very young and old
associated with poor dietary intake, excessive energy dense/nutrient light diets and extreme diets (removal of one or more food groups)
evidence
iron deficiency and anaemia (low Hb and iron stores) in adult women and older girls
low vitamin D status – implications for bone health
low functional riboflavin
others in normal range

Question 5

how can deficiency be linked to illness

Answer 5

alcohol liver disease – B1, D
IBD – iron, B12, D, K, folic acid, selenium, zinc, B6 and B1
Obesity – D, copper and zinc

Question 6

what are the major site of micronutrient absorption

Answer 6

Duodenum, jejunum and ileum

Question 7

what is vitamin C

Answer 7

Foods of plant origin
Absorbed at buccal mucosa, stomach and SI
Buccal by passive diffusion
GI rapid absorption by carrier mediated transport system
<20mg mucosal conc 98% absorbed, drops to 6% if >100mg
Deficiency can lead to scurvy

Question 8

what is vitamin B1

Answer 8

Common in all food
Absorbed in jejunum and ileum
At low conc absorbed by active Na+ dependant processes
Although con passive diffusion (>8 mg in single dose)
Deficiency can lead to Wernicke korsakoff syndrome

Question 9

what is vitamin B2

Answer 9

In most foods in co-enzyme form

Absorbed in SI by 2 stage process, released from proteins by proteolytic enzymes and hydrolysed by brush border enzymes

Question 10

what is vitamin B12

Answer 10

Synthesised by microorganism (in animals, not plants, concentrated by foods, can contaminate plants by soil bacteria)
Absorbed in distal portion of ileum by pepsin and HCL releasing it from proteins. B12 binds with transcorrin (aka R factor) released from salivary glands/ bile/gastric and pancreatic secretions. In jejunum released from TC to bind to IF (secreted by stomach). Complex binds to receptors in distal ileum for B12 to be absorbed
Pernicious anaemia

Question 11

Why are B vitamins important

Answer 11

B vitamins act as co-enzymes in citric acid cycle

B2 3 and 5 in ETC

Question 12

how to B12 and folate link

Answer 12

Folate and methionine cycles

Can mask deficiency in each other

Question 13

what is vitamin A

Answer 13

Long chain fatty acid found in animals, precursor to carotenoids found in plants
Absorbed in SI (carotenes in upper region D and J).
Animal proteins as Retinol complex hydrolysed by pepsin in stomach and other proteolytic enzymes then absorbed
Carotenes solubilised into micelles and absorbed through membrane and converted to retinol

Question 14

what is vitamin D

Answer 14

Animal food, synthesised in skin from UV light
SI 50% absorbed, Dietary vitamin D2 and UV light Vitamin D3
Absorbed from mixed micelles by passive diffusion into intestinal mucosal cell
Liver 25-hydroxylase enzymes convert D2 and D3 to main circulating form of vitamin 25-hydroxy-vitamin-D. This is active form as converted by kidney and other tissues (vitamin 1,25-dihydroxyvitamin D)

Question 15

what are risk factors for vitamin D deficiency

Answer 15

Pigmented skin
Lack of sunlight exposure
Skin concealing garments or strict sunscreen use
Elderly or housebound
Vegan/vegetarian or high phytate consumption such as in chapatis
Malabsorption (eg IBD, coeliac disease, pancreatic insufficiency)
Use of anticonvulsants, rifampicin, cholestyramine, anti-retrovirals
Immunity link – lots of functions in innate and adaptive

Question 16

how is vitamin D important for immunity

Answer 16

Reduced maturation, increased differentiation of macrophages, inc bacterial killing, lower cytokine production and antigen presentation
T-cells – reduce Th1 cytokines (reduce AI and allergies) and inc Th2 cytokines, dec immunoglobulins, inflammation and AI, inc suppression of TH cells

Question 17

what is calcium

Answer 17

inorganic element
Dairy and plant products
20-30% absorbed in acid medium
Vitamin D dependant calcium transport system when intake low and requirement high in D and passive in J when intake high
Primarily absorbed in duodenum and jejunum and fermentation of plant products in colon
Iron

Question 18

what is iron

Answer 18

inorganic element
Haem iron in animal food and non-haem in plant food
Primarily proximal SI
Haem iron absorbed as intact porphyrin complex and non haem ionised from ferric to ferrous form
35% of iron absorbed when stores are low. 5%with normal iron status

Question 19

what are the roles of iron in the body

Answer 19

component of cytochrome proteins that produce ATP in mt
boost immune system
helps prod nerve signalling NTs
necessary for DNA synthesis
synthesis of proteins
O2 binding site on Hb and myoglobin 
functional role in all cells

Question 20

what are the roles of calcium in the body

Answer 20

developmental 
egg activation
early embryonic events
L-R axis patterning 
organ development 
physiological 
bone formation
blood clotting
brain function and neurotransmission
heart function 
muscle function