Join Date: Mar 2012
Location: Helena, MT
It's kind of funny; I watched a TV special about hyponatremia today!
But honestly, they never shared that. Coming from my background in biology, I can only guess and use logic to answer your question: not really.
I get what you're saying. I'm assuming this is your logic: As water tends to dilute the blood stream, there is a stronger chance of ions rushing out of the cells to create a balance. If the [Na+] in the blood was say, 70 milliequivalents per liter (that's half of normal), and let's say the sodium level in one cell was 100 (made that up; I honestly don't know that average), then the sodium would be sucked out of the cell to equalize the sodium level inside the cell and inside the blood stream.
But see, there are issues with that logic. Of course, blood IS moving continuously, so chances of reaching total equilibrium are low, and our cells don't just rely on diffusion; we actually use a lot of active transport, voltage-gated ion channels, etc. Ions are NOT permeable to cell membranes; it requires active transport. Because of this, I would say what actually ends up happening is that cells are going to begin to swell up to try to equalize the sodium concentration. Water, as I'm sure you know, IS permeable to a membrane. There are two ways to change a concentration: change the amount of solute or change the amount of solvent. If you increase solute, you increase concentration. If you increase solvent, concentration decreases. So, for the cell that is has a concentration of 100 and the blood that has a concentration of 70, because the cell can't give up it's sodium readily, the only substance that can move is water, the solvent. So to decrease the concentration in the cell, water flows to the cell. Now, part of this is that the dilute concentration in the cell DOES cause issues. Having the same amout of ions (say, 500) doesn't matter; it's how many ions are there in relation to how much of the solvent. If you have a concentration of 70, sodium is much less able to react the way it needs to (remember, everything inside a cell is pretty haphazard- the molecules literally have to bump into each other to react). So, the cell can become hyponatremic- which is not good. However, on the flip side This would stabilize the blood's concentration, too, thus balancing it out a bit and saving yourself from that happening again, but lowering blood volume and actually lowering blood pressure, too
But, then, it's a lot more complicated than that... hormones, gene expression, etc can trigger what comes in and out of a cell. And, because cells are not just tightly packed (most of them are in a medium that contains free ions for the cells to use if it needs it), sodium levels do impact some things. Low sodium levels obviously can cause serious problems, but did you know sodium is actually used to fire neurons? It's one of the most abundant ions associated with forming the electrical current known as an action potential that eventually has the axon release signals at the synapse. Anyway, it's important, and as I've said before, our body does a lot to regulate the sodium levels.
So, my point is, yes, drinking a lot of water dilutes sodium levels in the blood, causing hyponatremia, but usually it isn't taking ions away from the cells. It is diluting the levels of sodium (and other essential nutrients). That's what causes hyponatremia. It's not just about what is in the blood per se but about what is in the cell. The cell needs a certain amount of sodium to function properly; with a low sodium level outside, if it needs more sodium, it can't get it, but also it can start to take in too much water and become hyponatremic that way.
People always say eat low sodium and drink a lot of water, but that's because a lot of people actually have hypernatremia. I know most people associate high sodium intake with average water intake as a sure-fire way to "bloat". But, remember where the water is. Having too much sodium ANYWHERE- in blood or in cells- is going to cause people to retain water. The only way sodium in the body cells can be flushed out is if the cells actively transport sodium out... and that's a lot less dependent on concentrations than we think.
^^ That's my logic behind it. I can't say I know 100% it's true because I haven't studied this enough to know all the ins and outs of cellular transports and especially haven't studied enough regarding the brain and how it regulates blood flow. I'm only a lowly undergrad right now (irony is I want to be a neurologist), so take that or leave it. I don't pretend to be a professional!
If you're worried about hyponatremia, start to ask yourself how you're feeling. Are you feeling more fatigued? Memory loss and difficulty to concentrate? How is your balance? If any of those seem off, ask a doc to do a complete blood ion analysis, especially because if you're too low in sodium due to drinking too much water, you might be too low in other ions too.