sodium Flashcards
is sodium the main intra cellular or extracellular ion
major extracellular ion – so concs outside cell are higher
Na conc in cells is low and varies with what and give an example
cell type
eg. 3-4 mmol/l in muscle and 20 mmol/l in red blood cells.
does Total body sodium vary between the sexes
yes
how many g of sodium is there in the average adult
90 - 100g
what the conc of sodium in men and women in mmol/kg
adult male 52-60 mmol/kg
adult female 48-55 mmol/kg
what percentage of body sodium is intracellular
10%
what percentage of body sodium is extracellular
50%
what percentage of body sodium is in skeleton
40%
(35-40 g)
(non-exchangable Na pool – i.e. not readily available)
Sodium content of unprocessed foods varies between what
0.1 and 3.3 mmol/kg
Processed foods have higher sodium content of what and why
11 to 48 mmol/100 g as is added
what is sodium added to foods for
enhancing taste, and preservative as has antibacterial qualities (sodium nitrate).
whats the link between processing level and sodium content
Higher the level of processing the higher the level of salt in the food
what percentage of our salt in the diet comes from bread and cereals
30-35%
what percenatge of diet intake of salt comes from salt addition during cooking or at table
35%
what do requirements of sodium depend on
on amount of sweat produced, so varies from country to country due to their climate temp
how much NaCl is adequate in temperate climates
2-3 g NaCl
(equivalent to LRNI; 4 g NaCl is equivalent to RNI)
why is sodium often expressed as sodium chloride
sodium is always present as a salt so is why its always expressed as this as this is what we consume
what are the RNI and LRNI for sodium on its own
LRNI: 25 mmol/d (conc) 575mg/d
RNI: 70 mmol/d (conc) 1 600 mg/d
what is the UKs intake of salt and which gender consumes the most
9-10 g/d (men usually consume more than women).
Excess sodium is normally excreted where
in the urine
explain sodium content in different foods in relation to processing
Low salt options are natural food – such as buying eggs and cooking them at home. Buying them processed will have added salt. Same happens with ready made soups. Same happens with fruits and veg such as with buying pre baked potatoes and chips, and ready meals.
Pre made sauces and seasonings have added extra salt
Desserts and sweet snacks also have extra salt added
what foods are fairly low in sodium
Wheat flour
Rice
Beef
Herring
Milk (cow)
Potatoes (boiled)
Carrots
Tomatoes (raw)
what foods are high in sodium
processed foods
white bread
rice crispies
beef sausage
bacon
tinned carrots
salted butter
what is the RNI for children under age 4 for sodium
500 mg/d equivalent to only 1.25 g salt/d
why can babies under age 1 not consume sodium
as have undeveloped kidney function and so cannot handle Na+
what happens to milk for babies as they cannot consume sodium
cow’s milk not suitable infant feed
breast milk provides about 500 mg NaCl/d, so human milk is fine
But 2-3 x this in cow’s milk than in breast milk
Infant formula/baby foods should be low salt. infant formulas removes the salt from the milk.
People who are unknowledged on this should be educated
why do we need sodium
Regulates
- electrolyte balance
- acid/base balance – these are tightly regulated
- conductive capacity of nerves
- muscle contractions
- production of adrenaline
- production of amino acids
Most important cation (electrolyte) in maintaining the volume of extracellular fluid (and osmotic concentration of the intracellular fluid)
what does changes in levels of sodium in extracellular fluid cause
movements of water into or out of cells
So if levels of sodium get high in extracellular fluid then it removes water out of tissues causing dehydration which is adverse to their function
Sodium in body is regulated via the what
renin-angiotensin-aldosterone system, which is under homeostatic control. Its very readily absorbed so will easily enter body.
what happens in states where sodium is depleted
aldosterone levels are increased and reduces urinary excretion of sodium.
aldosterone levels are controlled by what and what does it do
not sodium levels
The system is activated by loss of blood volume which causes a fall in blood pressure e.g. due to dehydration; haemorrhage.
Aldosterone system will reduce the urinary excretion reducing loss of sodium so it can be take back into body, dragging water with it, so conc can increase
describe high blood pressure
High blood pressures caused by generated force by the extra water and sodium in blood increasing the vein diameter and causing more force required to push the blood to the tissues
what is the definition of hyponatraemia
low level plasma Na+
indicates severe Na+ depletion.
what causes hypoantraemia
- e.g. excessive sweating (marathon in hot climate) – so why they take isotonic drinks
- e.g. fluid losses: diarrhoea#
- e.g. disease states: diabetes mellitus, Addison’s disease, medications renal failure –Na+ loss in urine
Any reduced body sodium pool leads to reduced what
extracellular fluid volume.
explain the impact of water excess and low sodium conc
ADH hormone controls excretion off water, ADH syndrome causes extra storage of water(cancers), renal failure, cirrhosis etc. – known as a dilutional hyponatraemia – low sodium conc as more water so diluting the sodium conc as in water excess.
Water excess cant occur by drinking too much water as we would pee it out. Something would have to disrupt the mechanism
what is the definition of hypernatraemia
high level plasma Na+
what does hypernatraemia indicate
H2O deficiency (rarely Na+ excess) i.e. Dehydration, but not always dehydration
explain insufficient water intake in relation to Hypernatraemia
