Can high sodium intake be offset by drinking a lot of water?

February 15, 2012 8:24 AM

Can high sodium intake be offset by drinking a lot of water?

I swear I read/heard somewhere recently that eating a lot of salt isn't really that bad as long as you offset it by drinking a lot of water--it was a relatively legit source (like NPR or something) or I would have just blown it off right away. This seems too good to be true, but I'd like to believe it as I am a salt fiend with a family history of high blood pressure who also happens to be a steadfast water-drinker. Has anyone else ever heard this, and if so, would you please point me in the direction of solid research to support it?

posted by lovableiago to Health & Fitness (10 answers total)

IANAD or human biologist, but from what I gather, the primary issue with salt intake is that it promotes fluid retention, increasing stress on the cardiovascular system. Sodium concentration in the blood is maintained at some equilibrium, so the more salt you eat, the more fluid your body will try to retain. I guess the alternative is that you eat more salt and drink less water, inducing hypernatremia by dehydration. But dehydration is not the mechanism that exposes your heart to additional stress.
posted by Nomyte at 8:32 AM on February 15, 2012

Can high sodium intake be offset by drinking a lot of water? In a manner of speaking, yes. However, extremes are never healthy, and in this case, you would just be making your kidneys work harder as you approach water intoxication and hyponatremia.

Worries about salt intake are kind of overblown -- a recent study has shown that lower salt intake doesn't do anything for heart disease, for example. "Lower sodium intake is recommended for people with high blood pressure and people with heart failure, but recommending it to the population as a whole, I wouldn't do without proving it's completely safe."

So, talk to a doctor. Are you generally healthy? You're probably fine. Don't drink too much water. Don't eat too much salt.
posted by Cool Papa Bell at 8:49 AM on February 15, 2012 [1 favorite]

Sort of. Your kidneys are the major organ responsible for regulating the salt content of your blood, along with different receptors in the cardiovascular system and brain which sense the salt in your blood (osmoreceptors). The receptors don't sense the actual amount of salt, in fact they measure more the concentration of salt in the blood (osmolarity).
When your blood contains more salt than it should, you could drink a lot of water, which would cause the concentration of salt to decrease, but it wouldn't necessarily decrease the overall amount of salt in your body. It this situation, you might feel bloated, and your blood pressure increases because you have a higher volume of liquid in your cardiovascular system.

So, now you have too much liquid in your cardiovascular system. Here a different set of sensors (baroreceptors), start telling your body that the blood pressure is too high. Together, both barosensors and osmoreceptors can signal to your brain that your blood pressure needs regulating. Your brain, in turn, tells your kidneys to go to work. The major way that your kidneys affect blood pressure is by regulating the amount of water and sodium that is allowed to leave the blood. Eventually, your kidneys could probably eliminate all the extra water and sodium. But I think it is probable that such a situation would put strain on your kidneys, and wouldn't really help if you were constantly eating too much salt and a lot of water.

Unfortunately, if you are unlucky enough that you have to reduce salt intake to help your blood pressure problems, I don't see that increasing water intake is the best solution long-term.
posted by nasayre at 9:08 AM on February 15, 2012 [1 favorite]

I'd be worried that you'd lose too many other electrolytes as you pee out the excess water and sodium. You'd probably end up low on potassium, at least, which is bad for your heart function in other ways.
posted by vytae at 9:15 AM on February 15, 2012 [2 favorites]

So would something like water pills (which I'm told make you pee lots and drop water weight) help balance salt intake?

I don't eat a lot of salt on my food, but being single I do eat a lot of frozen dinners which I know are high in sodium...
posted by myShanon at 9:27 AM on February 15, 2012

The news stories were not about merely drinking a lot of water, but instead eating a lot of potassium-rich foods. It's the sodium:potassium ratio that appears to matter most. See, for example, Sodium and Potassium Intake and Mortality Among US Adults.
posted by Ery at 9:36 AM on February 15, 2012 [1 favorite]

Yeah. Get more potassium.

As i understand it, sodium and potassium work together to regulate "membrane potential" in the cell wall; sodium is concentrated outside the cell while potassium is concentrated within. Membrane potential provides the electrical charge needed for a bunch of cell functions, and is especially important for muscle and nerve cell functions. Our bodies are batteries.
posted by notyou at 10:27 AM on February 15, 2012 [1 favorite]

Everything said above is true. Eating a lot of salty food will make you thirsty precisely because your body is trying to keep everything properly balanced. High sodium intake can make you retain more water, which can easily push your blood pressure too high, which is very bad over the long term. But everyone is different -- some people need to restrict sodium intake, some don't.

You don't need to guess or speculate, or decide which medical studies to believe or ignore, or learn a lot of biochemistry. Go directly to the source -- your own body -- to evaluate whether your preferred diet is working well for you. If your blood pressure and kidney function are fine while you're eating what you enjoy, no worries. Next time you see a doctor, talk a bit about your concerns. You're not looking for the medical gospel about what's best on average for the population as a whole; you only need to know what works for you. You can check your BP at home every now and then if you want to be very sure it's staying in line, and your doctor can do basic blood and urine tests to check your kidney function once a year or so. If you don't have a problem, you don't need a solution.
posted by Corvid at 11:09 AM on February 15, 2012 [1 favorite]

Came here to comment on the sodium-potassium ratio. I've seen a few articles about that and it sounds like eating more potassium will offset the sodium more than water alone would.
posted by fromageball at 6:49 PM on February 15, 2012

Answer to myShanon regarding "water pills", no. Generally what people mean by the lay term "water pills" is diuretics, which do make you pee a lot, but depending on which diuretic you take they can end up causing low potassium levels (specifically the two most common diuretics, hydrochlorothiazide/HCTZ and furosemide/Lasix).

But to get at the more important issue, there's a reason why your body tries to maintain a certain ratio of sodium to water. If you try to upset that balance, you're going to end up with a sodium level that is too high or too low, and that can be lethal - for examples, see stories of death resulting from water drinking contests ("water intoxication"), or in the case of people who can't take in enough water to balance out their sodium levels, deaths from dehydration.

Nthing the need to increase potassium intake. But keep in mind that if you take in enough sodium, there comes a point when potassium can't help you anymore. There is no magic bullet. You should still watch your salt.
posted by treehorn+bunny at 11:31 PM on February 15, 2012