Week 11 revision questions Flashcards
Difference between major and minor minerals
- major >100mg per day
- minor <100mg per day
major minerals
- Sodium
- Potassium
- Chloride
- Calcium
- Phosphorus
- Magnesium
- sulfur
Influences mineral conc in food
- genetic variation in animals (absorption pathways of nutrients from soils and feed)
- variation in mineral content in soil
- in refined pllant produces - milling removes iron, selenium, zinc and copper etc
Factors impairing mineral bioavailability
o Excess fibre (above 38g/day) can lead to lower mineral status
- Phytic acid found in fibre (phytate in legumes and whole grains): binds to minerals & leads to excretion
- Oxalic acid in dark green leafy vegetables (not associated with fibre) : binds minerals and makes them less bioavailable E.g. calcium in spinach: 5% absorbed versus 32% for calcium from dairy
- Polyphenols and tannins can reduce bioavailability of iron and calcium in particular e.g. black tea, dark chocolate, red wine (all contain high levels of tannins that interfere with iron absorption)
- antacids may impair bioavailability of minerals, because of reduced stomach acidity
Factors facilitating/increasing mineral bioavailability
- Vitamin C: improves non-haem iron absorption within the same meal
- Stomach acidity: assists in converting minerals from 3+ to 2+: helps their absorption (as 2+ is the absorption form od minerals)
- Leavened breads with baker’s yeast may break the bonds between the phytates and the minerals: ↑ bioavailability of minerals
- Good vitamin D status facilitates dietary calcium absorption (because vitamin D receptor and calcitriol are involved in the active transport of calcium absorption)
- Human absorption of minerals increases when needs are greater
Main anion and cation in ECF
cation - Sodium
anion - chloride
Main anion and cation in the ICF
cation - Potassium
anion - phosphorus
Sodium comes from the diet
1 - processed foods 77%
2 - naturally occuring 12%
3 - added to food on plate 6%
4 - added to food during cooking 5%
Conversion of sodium to salt
/0.393
conversion of salt to sodium
*0.393
hypertension
Chronic elevation of blood pressure (pressure exerted by blood flow against blood vessels measured in mm Hg
DASH
Dietary approach to stop hypertension
- high potassium to sodium ratio (4700mg:2300mg)
major functions of calcium with their mechanism
- Bone development and maintenance:
- Forms calcium-hydroxyapatite along with phosphate
2- Blood clotting: calcium involved in the blood clotting factors formation cascade. Ca binds to the gamma carboxy glutamic acid in prothrombin - Muscle contraction:
- Calcium ions released when nerve impulse reaches myocytes
- Calcium triggers muscle proteins to contract - Transmission of nerve impulses
Influx of calcium ions when nerve impulse reaches cell
How can potassium assist in reducing hypertension in salt sensitive people?
by trying to achieve high potassium to soidum ratio to induce excretion of sodium->excretion of water->reduce blood volume->reduce hypertension ???
Is having a high calcium diet the only factor for good bone density?
nope bone building nutrients include more than calcium: potassium, vitamin D, vitamin K, protein, magnesium, vitamin C, phosphorus, copper as well as exercise
Contrast/compare a typical high sodium with a high potassium diet, based on the kind of foods they would contain, and their nutrient density
Sodium
high in processed foods, low nutrient density, low in fibre.
Potassium
high in fresh unprocessed and whole foods, nutrient dense, high in fibre.
nutrients important in bone health
Potassium - stops Ca++ excretion (acid base balance -> preventsCa2+ being used as buffer)
Calcium,magnesium and phosphate- form calcium hydroxyapatite to form collage
magnesium
Vit K - cofactor in carboxylation reaction for bone protein
Vit D - enhances calcium absorption
Vit C - cofactor in hydrolase enzyme involved in collagen formation
Protein - amino acid provision for collagen and bone protein
How does the DASH aim to address hypertension?
- high potassium to sodium ratio to induce excretion of sodium -> excretion of water -> reduce blood volume -> reduce hypertension
- calcium can act as a smooth muscle relaxant
- magnesium can act as a vasodilator
2 and 3 make blood vessels more flexible and adapt to blood volume thus reduce blood pressure - fibre - helps cholester to bind to bile so excrete it -> dont reabsorb it -> forces body to produce more bile -> need to use blood cholesterol and therefore minimilising cholesterol absorption
- also appetite control
know mechanism by which calcium homeostasis is maintained in body - low level
low level -> parathyroid gland produces PTH -> promotes bone reabsorption -> increases synthesis of calcitriol -> increase calcium absorption in SI ->normal
know mechanism by which calcium homeostasis is maintained in body - high level
high level -> thyroid gland produces calcitonin -> stops bone absorption -> promotes excretion of calcium through kidney -> normal
Phosphorous absorption is promoted by
hormone calcitriol
oxalic acid found in
green leafy vegetables - bind to minerals and impair absorption by decreasing bioavailibility
phytic acid found in
fibre - bind to minerals and impair absorption by increasing excretion
calcium is more bioavailable in
dairy foods
