Hypertension & Macrominerals: "Sodium", Potassium, Chloride Flashcards
What are the steps/framework for updating the DRIs?
steps:
1. Review and select the indicator(s) that will inform the DRIs
- Assess intake-response relationships and establish DRI
- Compare current population intake levels to DRI values
- Discuss public health implications and special considerations
Following guiding principles report on establishing DRIs for chronic disease endpoints:
-est. when there’s at least moderate strength of evidence for both casual and intake-response relationships
-ideally based on the chronic disease of interest
tho qualified surrogate markers can be used as supporting evidence
What are the DRs for toxicity and disease reduction?
UL: tolerable upper limit
based on toxicity endpoints
CDRR: chronic disease risk reduction (CDRR)
- based on reducing risk of chronic disease
- reduction of intakes above the CDRR: expected to reduce chronic disease risk within the apparently healthy pop.
What is sodium? (amount in body)
Constitutes ~93% of cations in body total amount = 105 g in 70 kg man ~30% on surface of bone crystals ~60-70% of sodium found in ECF ~10% IC in nerve and muscle tissue
What are some sources of sodium?
~75% sodium currently consumed added during processing & manufacturing food
(used for flavoring and as preservative)
~12% found naturally in food
11% from table salt and added to cooking
1 tsp salt has 2.3 g Na
<1% from tap water
prehistoric diet not high in salt
Are sodium found in salt?
all types of salt are high in sodium
Kosher salt, sea salt…etc.
No healthier choices
What are some sources of sodium in diet?
Most sodium we eat does NOT come from salt shaker but from:
processed food (deli meats, pizza…)
Packaged and ready-to-eat foods
fast foods, restaurant
also found in: salt, sauces, condiments, dressing added during cooking
Naturally small amount in food (milk, fresh meat, fresh/frozen veg.)
What are some other names for sodium?
baking powder, baking soda, brine, onion salt, soy sauce
What are Daily values?
based on HIGHEST recommended intakes
apply to most ppl >2yo
not included extra nutrient needs for preg./lactating women
set by Health Canada
How is sodium absorbed?
~95-100% ingested sodium is absorbed in SI
0-5% excreted in feces
3 basic pathways involved:
-BBM: Na+/glucose cotransporter (throughout SI)
- an electroneutral Na+/Cl- cotransporter exchange (SI and proximal colon)
- electrogenic Na+ absorption mech. (colon)
transported freely in the blood (i.e. not bound to protein)
How does Na+/glucose cotransporter absorb sodium in enterocytes?
Carrier on BBM of enterocyte cotransport sodium together w/ solute (ex. glucose) into the cell
once inside cell Na+/K+ ATPase pump Na+ across basolateral membrane
(glucose exit via facilitated diffusion)
How does Na+/H+ exchange work?
Na+/H+ exchange works in concert w/ a Cl-/HCO3- exchange
-sodium is then pumped basolaterally with Cl- diffusion passively
sodium is pumped basolaterally w/ Cl- diffusing passively
How does electroneutral Na+ and Cl- absorption work?
Sodium enters the luminal membrane via Na+ channel
*Common driving force for Na+ absorption is the inward directed gradient created by the basolateral Na+/K+ ATPase pump (maintains low IC Na+)
What are some functions of sodium?
Serum Na+, K+, and Cl- are maintained within narrow range (~135-145 mEq/L)
(electrolyte balance)
Na+, K+, Cl- maintain osmotic pressure = fluid balance among body compartments
(e.g. blood volume, IC volume)
Na+ role in nerve transmission & muscle contraction (AP)
Na+ is major EC cation
What is the main role of Na+/K+ ATPase
Potassium: major IC cation
principally charged ion in cells
Na+ and Cl- abundant EC
Na+/K+ ATPase maintains conc. gradient
pump accounts for 20-40% resting energy in adults
(2 K+ into cell, 3 Na+ out)
What is the role of Na+ and K+ in nerve conduction and muscle contraction
Stimulus changes membrane permeability to Na
Na+ rushes into cell
–>reverse/depolarizes charge of cell at that location
an electric current is generated
How does sodium Na+ regulate blood pressure?
Decrease in blood volume typically decrease BP
- A decrease in BP triggers kidney to release the enzyme renin
- Renin converts angiotensin to Ang I
- ->ACE converts it to Ang II - Ang II increases BP by constricting walls of bvs
- Ang II stimulates release of aldosterone from adrenal gland
- Aldosterone increases sodium reabsorption by the kidneys
- water follows sodium
- ->helping to maintain bv and BP
How do we excrete sodium?
Excess Na of what is needed is excreted via kidneys and sweat
Aldosterone: major hormone that controls Na+ excretion
What are some interactions of Na+ w/ other nutrients?
Dietary Na+ intake increases urinary calcium excretion
mitigated at least in part by increased absorption
How do we assess the level of sodium in body?
24h urinary sodium excretion level
collection of multiple 24-h samples is best to assessment due to day to day variability
What are some Sodium reduction strategy Canada has taken/proposed?
published in 2010
- sodium reduction targets for foods’ defined time lines: VOLUNTARY appraoch
- mech. for public commitment by industry to the targets
- plan for independent evaluation of success of the program w/ option of taking stronger measures as necessary depending on progress
2012 Health Ca. published Voluntary targets for … by end of 2016
-develop through consultation w/ industry
encourage gradual reduction
maintaining food safety, quality, and consumer acceptance
What was the outcome of the sodium reduction strategy carried out by Ca?
some progress, not as much as anticipated
processed food decreased only 240 mg (8% in average daily sodium intake)
86% food categories did not meet final targets
Voluntary approach did NOT work
