Lecture 13 Flashcards
What is the evidence of micronutrient deficiency in 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 deficiencies are associated with illness
Alcohol liver disease – thiamine (B1), Vitamin D,
Inflammatory Bowel disease - iron, B12, vitamin D, vitamin K, folic acid, selenium, zinc, vitamin B6, and vitamin B1
Obesity – vitamin D, copper, zinc
Discuss the dietary source, site of absorption and mechanism of absorption of vitamin C
DS- Foods of plant origin
SA- Buccal mucosa, Stomach, Small Intestine
MA-Buccal – passive diffusion
Gastrointestinal absorption is rapid and through carrier-mediated transport system if mucosal concentration less than 6mmol/L
<20mg ingested – 98% absorbed
>100mg ingested 6% absorbed
Scurvy
Discuss the dietary source, site of absorption and mechanism of absorption of vitamin B1
DS- Common in all food
SA- Jejunum and Ileum
MA- At low concentrations by active Na+ dependent processes
At high concentration (>8mg in a single dose) passive diffusion
Wernicke Korsakoff syndrome
Discuss the dietary source, site of absorption and mechanism of absorption of vitamin B2 riboflavin
DS- In most foods in co enzyme form
SA- Small Intestine [SI]
MA- 2 stage process released from proteins- proteolytic enzymes and then hydrolysed by brush border enzymes
Discuss the dietary source, site of absorption and mechanism of absorption of vitamin B2
DS- Synthesised by micro organisms – in animals but not plants. Concentrated through food chain
On plants – contamination by soil bacteria
SA- Ileum – distal portion
MA- 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 the stomach
B12 –IF complex binds with receptors at distal ileum and B12 is slowly absorbed
Pernicious anaemia
Discuss the dietary source, site of absorption and mechanism of absorption of vitamin A
DS- Long chain fatty acid found in animals
Precursor – carotenoids found in plants
SA- Small Intestine [SI]
Carotenes upper region of SI (duodenum and jejunum)
MA- 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
Discuss the dietary source, site of absorption and mechanism of absorption of vitamin D
DS- Animal food
Synthesised in skin from UV light
SA- Small intestine 50% absorbed
Dietary Vitamin D2
UV light Vitamin D3
MA- 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.
What are the risk factors of 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
Discuss the dietary source, site of absorption and mechanism of absorption of calcium
DS- Dairy products Plant products SA- Primarily Duodenum Jejunum Fermentation of plant products - colon MA- 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
Discuss the dietary source, site of absorption and mechanism of absorption of iron
DS- Haem iron in animal food
Non-haem iron in plant food
SA- Primarily proximal small intestine
MA- 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
