Medical Does the net charge of sodium and chloride ions cancel out in salt consumption?

[mktsgm]

It is generally said that excess salt consumption leads to water accumulation as a compensating mechanism as the cations of sodium builds up excessively.

My doubt is, if the sodium chloride (salt) consists of chloride (anions) as many as sodium (cations), don't the net effect of the increase of ions cancel each other? Why don't the chlorides give counter ion effect?

It seems I miss some important theory here. Kindly elucidate. Thanks.

 

[BvU]

Both ions like to be surrounded by water (hydrated). The important effect here is the osmotic pressure that builds up.

 

[BillTre]

In water, the ions (mostly) dissociate, resulting in two particles (the Na⁺ and Cl^-) from the single original NaCl molecule.
Osmotic and related collogative properties are related to the number of independently moving particles in the solution.
It is my understanding that this drives the thermodynamics of the system and osmotic differences of solutions.

 

[Delta2]

ok so the "stupid" (though it is being said there are no stupid questions , maybe only stupid answers) question I want to ask:

The osmotic pressure due to concentration of Na+ ions isn't canceled out by the osmotic pressure due to Cl- because they have equal and opposite charges?

 

[Ygggdrasil]

The osmotic pressure due to concentration of Na+ ions isn't canceled out by the osmotic pressure due to Cl- because they have equal and opposite charges?

No. Osmotic pressure depends only on the total concentration of dissolved particles, irrespective of whether they a positive charge, negative charge or no charge.

 

[jim mcnamara]

I think we are looking at this backwards. Renal (kidneys and friends) systems and sweat glands are the way out of the body for sodium. For a variety of reasons mostly relating to environmental factors like the K/Na (potassium/sodium) ratio in the long term diet, and the functioning of the renal system, water is held osmotically in tissues because the body cannot or will not excrete sodium fast enough.

Considering just diet in healthy people, modern humans consume far higher sodium than in the past, and potassium consumption is down slightly, so the ratios of the past with K >> Na have nearly reversed with Na nearly equal to K.

Here is a new paper discussing outcomes for patients when lowering sodium and increasing potassium, i.e, changing the K/Na ratio, and why worrying about both is important for clinicians: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5537815/

Before you ask: Cook and eat without any salt added. If you use fresh foods or preserved foods with low sodium, things will work out just fine, K/Na -wise. No worries. So now you know at least one of several reasons why many countries require nutrient labeling on processed/preserved foods.

PS: RDI for Na is 1500mg Na per day and 4200mg K per day. On diets like the one above: ~1000-1500mg Na and ~4000mg K

 

[BvU]

The osmotic pressure due to concentration of Na+ ions isn't canceled out by the osmotic pressure due to Cl- because they have equal and opposite charges?

It's not a stupid question, but for this effect the sign of the charge doesn't play a role.

Both ions like to be surrounded by water (hydrated). The important effect here is the osmotic pressure that builds up.

The sign of the charge of the ion makes that the water molecules around the positive Na⁺ ion have their (slightly negative) oxygen side towards the Na⁺ ion. And the water molecules around the negative Cl^- ion have their (slightly positive) hydrogen side towards the Cl^- ion. See the last few seconds here (or check out one of the then following videos).