Micronutrients Flashcards
Why are vitamins and minerals useful?
Vitamins, minerals and trace elements are fundamental groups of nutrients to sustain life
They have a physiological role at the cellular level
How do vitamins work?
Vitamins often acting as co-enzymes in metabolic pathways
How do minerals and trace elements work?
Minerals and trace elements participate in wide ranging cellular mechanisms
What are processed foods considered to be?
Energy dense and micronutrient light
In which food groups are the micronutrients found?
All of them
Why are foods fortified?
To manage population deficiency
Who are we concerned about regarding micronutrient deficiency?
Generally population is well nourished BUT…
Concerns about marginalised groups, minority groups, the very young and the very old are associated with
-Poor dietary intake
-Excessive energy dense/nutrient light diets
-Extreme diets (removal of one or more food groups)
What evidence is there of a micronutrient deficiency in the UK?
There is evidence of iron-deficiency anaemia (as indicated by low haemoglobin levels) and low iron stores (plasma ferritin) in a proportion of adult women and older girls. This is in line with findings from previous surveys and does have health implications for these groups.
There is evidence of low vitamin D status in adults and older children, both male and female. This has implications for bone health, in particular increased risk of rickets and osteomalacia.
A substantial proportion of adults and older children have functional riboflavin (B2) status values indicative of low status. However the health implications of this are not known.
There is no evidence, at a population level, of low status for other micronutrients where normal ranges or thresholds for low status have been set. Levels of vitamin C, B6, B12, thiamin, retinol and vitamin E fell within the normal range.
What micronutrient deficiency is most closely associated with alcohol liver disease?
Thiamine (B1)
Vitamin D,
What micronutrient deficiency is most closely associated with Inflammatory bowel disease?
iron, B12, vitamin D, vitamin K, folic acid, selenium, zinc, vitamin B6, and vitamin B1
What micronutrient deficiency is most closely associated with Obesity?
Vitamin D
Copper
Zinc
Where is the most common source of vitamin C?
Foods of plant origin
Where is the site of vitamin C absorption?
Buccal mucosa
Stomach
Small Intestine
Describe the mechanism of absorption of vitamin C
Buccal – passive diffusion
Gastrointestinal absorption is rapid and through carrier-mediated transport system
if mucosal concentration less than 6mmol/L
What is the relationship between quantity and absorption of vitamin C?
<20mg ingested – 98% absorbed
>100mg ingested 6% absorbed
What does vitamin C accelerate the absorption of?
Iron
Where is vitamin B1 found?
In most food
Where is vitamin B1 absorbed?
Jejunum and ileum
Describe the mechanism of absorption of B1
At low concentrations by active Na+ dependent processes
At high concentration (>8mg in single dose) passive diffusion
What is the name of a deficiency of B1?
Wernicke Korsakoff syndrome
Where is vitamin B2 (riboflavin) found?
In most food as a coenzyme
How is B2 absorbed?
Small intestine
How is vitamin B2 absorbed?
2 stage process released from proteins - proteolytic enzymes and then hydrolysed by brush border enzymes
Where is vitamin B12 found?
Synthesised by micro oganisms – in animals but not plants. Concentrated through food chain
On plants – contamination by soil bacteria
Where is vitamin B12 absorbed?
Ileum
How is vitamin B12 absorbed?
Pepsin and HCL release B12 from proteins
B12 binds with transcorrin[TC] (also known as R Factor) released from salivary glands/in bile/ gastric and pancreatic secretions.
In jejunum B12 released from TC and binds to intrinsic factor [IF]released from stomach
B12 –IF complex binds with receptors at distal ileum and B12 is slowly absorbed
What is the deficiency of vitamin B12?
Pernicious anaemia
Where is vitamin A found?
Long chain fatty acid found in animals
Precursor – carotenoids found in plants
Where is vitamin A absorbed?
Small Intestine [SI]
Carotenes upper region of SI (duodenum and jejunum)
Describe the mechanism of vitamin A absorption?
Protein- Retinol complex hydrolysed by pepsin in stomach and other proteolytic enzymes in SI and then absorbed
Carotenes solubilised into micelles absorbed through membrane and converted to retinol
In terms of sites of micronutrient absorption, does length matter?
Yes- many different micronutrients absorbed in different places since many different mechanisms and conditions are required
Give some sources of vitamin D
Animal food
Synthesised in skin from UV light
Where is vitamin D absorbed?
Small intestine 50% absorbed
Dietary Vitamin D2
UV light Vitamin D3
How is vitamin D absorbed?
Absorbed from mixed micelle by passive diffusion into intestinal mucosal cell.
The liver 25-hydroxylase enzymes convert vitaminD2 and D3 to the main circulating form of the vitamin, 25hydroxy-vitaminD – also known as 25(OH)D. This is then converted by the kidney and other tissues to the active form of the vitamin 1,25-dihydroxyvitamin D.
Name some fat soluble vitamins
A
D
K
E
Name some water soluble vitmains
C
B1
B2
B12
List some risk factors for vitamin D insufficiency and deficiency
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
Name some inorganic molecules
Iron
Calcium
Where is calcium found?
Dairy products
Plant products
Where is calcium absorbed?
Primarily Duodenum
Jejunum
Fermentation of plant products - colon
Describe the mechanism of absorption of calcium
20-30% is absorbed in an acid medium
Vitamin D-dependent calcium transport system when intake is low and requirement high (duodenum)
Passive process when intakes are high – Jejunum
Where is iron found?
Haem iron in animal food
Non-haem iron in plant food
Where is iron absorbed?
Primarily proximal small intestine
Describe how iron is absorbed
Haem iron is absorbed as intact porphyrin complex
Non-haem iron ionized from ferric to ferrous form
35% of iron absorbed when stores are low. 5%with normal iron status
How can deficiency occur?
Treatment and illness
