Is it true that you can counter excess salt intake by consuming more water?
Thanks,
Rob
For the most part, yes. Without getting into too much detail, here’s what happens:
The salt (NaCl) gets into your bloodstream. The extra amount of Na and Cl increase the osmotic pressure of the blood. Since cells all have semi-permeable membranes, and physics being what it is, the body has to take fluid from the cells and interstitial space to equalize the osmotic pressure in the blood. This both lowers the osmotic pressure of the blood and increases the osmotic pressure of the cells and interstitial space until they equal each other. Your kidneys will then make concentrated urine, which as the name suggests has more salt (Na and Cl) in it than normal. With the excess salt removed from the blood, it now has a lower osmotic pressure than the cells and interstitial fluid, so it can give water back to them and everyone is happy.
But, if you take in too much salt, and your kidneys can’t remove it fast enough, more fluid has to be taken from the cells and interstitial space. If you keep taking in too much salt, or you had too much initially, then the amount of fluid taken is too great, and the cells crenate (shrink.) If too much crenation occurs, then there isn’t enough fluid for a cell to work, and it dies. If too many cells start to die, then you’ll start to suffer from dehydration, and eventually die.
But, if you take a lot of water with that salt, then you can avoid the problem. The salt and the water will get into the blood at about the same time (the water a little bit first actually, IIRC.) If the water you take in makes the total solution of water and salt isotonic (ie, the same osmotic pressure as the cells in your body,) then no fluid has to be taken from the cells. You kidneys will then remove both the excess water and excess salt, and you’ll be just fine.
But if you take in a LOT of salt initially, or your kidneys aren’t up to par, then this might not always work. Eventually, you will run into a scenario where you can take in too much salt, even with drinking a lot of water.
Even thought I’m not the OP, thank you for the explanation. I read this in one of Alton Brown’s books, and I’m a bit relieved to know he was right. 
ETA: ‘this’ being that the amount of sodium in food wasn’t really an issue as long as you drank plenty of water.
I’ve always wondered why people aren’t told to drink more water instead of eliminating salt from their diet. Coming from a family with grandparents who didn’t put salt into any food they ever cooked, I know that I’d much prefer the “drink more water” approach.
I don’t feel as if I can fully address the OP, but I think it’s worth throwing in a word of caution about this idea that you can just cancel out your salt intake with water. First, barring any acute medical crisis from water intoxication or consuming a very large amount of salt over a short period, I presume that we’re putting the risks of salt intake in the hypertension and its associated health risks.
Kidney physiology is a compex thing. Yes, theroretically increasing water intake will facilitate sodium clearance by the kidneys. But also, theroretically your kidneys should easily be able to handle a relatively high salt diet anyway even if you have a very low urinary output. Nevertheless, the relationship between salt intake and hypertension is well established. The homeostatic regulatory mechanisms that govern this have not been entirely elucidated, and we don’t know exactly why a high salt intake can lead to hypertension.
In the absence of experimental data demonstrating that increased water intake has a protective effect against sodium mediated hypertension, just saying, “screw it, pass me the TV diner with 2,300 mg of salt and a glass of water,” doesn’t strike me as the conservative line of thought. I believe the topic of the folly of taking medical or diet advice over internet message boards has come up a time or two before in these parts.
Every diet plan and other dietary healt advice I’ve seen says to drink aat least eight glasses of water every day. Of course the fine print says that that water total can include all forms of liquid (except alcohol).
Is alcohol neutral in its effect on hypertension? If I drink a bourbon and sparkling water (or very low sodium seltzer), am I mitigating the salt balancing effects of the water?
Yeah, but most diets are bunk and based on junk science.
What threemae said.
Basically, cutting down on salt intake has been shown (in appropriate double-blinded trials) to decrease blood pressure, decrease the risk of developing hypertension, and to decrease morbidity and mortality in folks with congestive heart failure.
Just adding more water has not been shown to decrease blood pressure or the risk of hypertension, and has been shown to actually increase morbidity and mortality in folks with CHF.
Everyone wants a softer, easier way, don’t they? And that includes me, too.
As Pops Mercotan used to tell me (usually after he observed me looking for an excuse to not do what I ought to), “everybody wants to go to heaven, but noone wants to die”.
Sorry, I’m gonna have to disagree with you bouv. To a very large extent, salt and water are regulated by independent mechanisms. Ingesting more water will have little effect on your net salt balance.
Salt (i.e. Na[sup]+[/sup]) in the bloodstream is a major determinant of blood volume. Blood volume is tightly regulated and a number of hormonal systems will be activated if blood volume is getting too high (or, even more critically, too low). For example, assuming that everything is functioning normally, increased salt intake, by virtue of tending to increase blood voluem, will lead to inhibition of the renin-angiotensin system and stimulation of natriuretic (salt losing) hormones. The net effect will be loss of salt in the urine and a decline in blood volume. This will occur whether or not water is co-ingested.
On the other hand, water in the body and bloodstream is regulated by another hormone - ADH (antidiuretic hormone). ADH causes water (but NOT salt) to be held onto by the kidney. Among other factors, ADH is released if blood osmolality rises or if blood volume decreases. Conversely, it is turned off when osmolality decreases or blood volume increases.
Given that the effect of taking in salt will be to raise blood volume, it follows that taking in salt will inhibit ADH. That will lead to water loss by the kidneys. So, drinking lots of water simultaneously while taking in salt will simply provide even more water for the kidneys to pee out due to the suppressed ADH levels. If anything, then, taking in water at such a time will tend to prevent loss of water from the bloodstream and body cells. In some sense that would actually augment the effect of the salt intake to raise blood volume. Regardless, it won’t counter the increased salt intake.
One last point. I suppose one could argue that taking in water with salt would tend to increase blood volume even more than by taking in salt alone. As mentioned above, increased blood volume leads to hormone changes which promote salt loss by the kidneys (i.e. in order to get blood volume back towards normal). So, if water and salt were both taken in, the blood volume might increase more than occurs when only salt is ingested. Hence, the hormone changes to promote urine salt loss would be especially stimulated. Alas, the flaw in this argument is that water ingestion has essentially NO effect on blood volume (only about 1/12 of ingested water stays in the blood). Hence, ingesting water with salt doesn’t help stimulate salt loss by the kidneys.
You da man, KG!
I asked this same question a few years back, and basically, it’s a bad idea.