11 ms·

Our understanding of the way the body handles salt may be wrong

195 points by mherrmann 9y ago

xaedes 9y ago
That is interesting. I see an advantage this adaption offers when trapped with only salty sea water. Excessive salt intake may occur naturally when in the ocean for whatever reason. When this reduces thirst and offers an (internal) alternative for water this may help you survive until you strand somewhere to find fresh water. Not the worst trait evolution could select for.
- Freestyler_3 9y ago
  There is a negative side to it, you use up more calories. (unrelated, I think fast food companies are already aware of the more hunger from salty food.)
Mz 9y ago
And, Dr. Titze said, high glucocorticoid levels are linked to such conditions as osteoporosis, muscle loss, Type 2 diabetes and other metabolic problems. And cystic fibrosis, which is perhaps best tldr'd as a salt wasting condition, frequently leads to Cystic Fibrosis Related Diabetes, which is neither type 1 nor type 2 diabetes.
- carbocation 9y ago
  CFTR, being a chloride channel, most likely leads to diabetes as a consequence of its effects on the voltage-regulated insulin release in beta cells from glucose sensing. [1] It strikes me as unlikely to be related to the salt-wasting that occurs from failure to reabsorb chloride in the epithelium. 1 = https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4104438/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4104438/
  - Mz 9y ago
    I think it is probably a lot more complicated than that. CF does a great many things to the body. It is an inflammatory condition and I have seen multiple articles linking diabetes and inflammation. People with CF tend to be seriously underweight and I have recently seen articles that link inadequate muscle protein to insulin resistance. There is no doubt more than that going on, those are just a couple of things that occur to me off the top of my head.
    - carbocation 9y ago
      "I think it is probably a lot more complicated than that." That's an evergreen, accurate response to anything in human biology!
      - Mz 9y ago
        So you're saying I'm right! ;-)
    - Steer 9y ago
      It would be nice of you to provide some sources for your claims. I don't know if you are right or not, but at least providing links to the articles you are referring to would be appreciated.
      - Mz 9y ago
        Diabetes and inflammation is actually easily googled, but here is a respectable source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1087185/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1087185/ PDF: The underappreciated role of muscle in health and disease http://ajcn.nutrition.org/content/84/3/475.full.pdf http://ajcn.nutrition.org/content/84/3/475.full.pdf There is a long and wordy section about muscle and insulin resistance, some choice outtakes: However, over the past few years it has become evident that changes in the metabolic function of muscle itself plays a more direct role in the genesis of insulin resistance than previously appreciated. (This is rebutting the idea that higher fat levels explain insulin resistance.) as little as a single bout of exercise [thereby stimulating triacylglycerol deposition in muscle intramuscular triacylglycerol (IMTG) oxidation] can transiently reverse insulin resistance (44). The section concludes with: Regardless of the specific intracellular mechanisms at the molecular level, it is clear that insulin resistance is not simply the result of increased fat mass and release of FFAs into plasma at an accelerated rate, with the muscle responding to elevated plasma FAA concentrations. Rather, alterations in the metabolic function of muscle are central to the development of insulin resistance and ultimately diabetes. I am not finding an exact point at which it explicitly says "Muscle loss causes insulin resistance" but that was my personal takeaway from reading this some time back. (On the other hand, maybe it does explicitly say that and I am just rushed for time and have crap eyesight, so maybe I am just not finding it. Whatever.)
reitanqild 9y ago
I think Thor Heyerdahl or someone on one of his crews noted that when they added seawater to the freshwater to make it last longer it also made them less thirsty. IIRC they thought it was an interesting observation since it was against all common understanding, but I don't think they ever came close to a solution to why.
- abovemypaygrade 9y ago
  Did he (or they) happen to mention the ratios of salt water to fresh? I don't know a whole lot about this topic, but I do recall reading somewhere that thirsty seafarers who succumbed to the urge to drink seawater ended up dying more quickly. I wonder if they figured out how much was okay to drink before it started negatively impacting health.
  - pilsetnieks 9y ago
    The negative impact is due to water loss via vomiting or diarrhea, and thus having a negative water balance. It's not like saltwater in itself kills you. In fact, you could drink the water of some less salty seas, e.g. the Baltic Sea.
    - int_19h 9y ago
      The real bad impact is from disrupting the way your kidneys work. Basically, seawater has a higher concentration of salt than it is possible for your kidneys to remove via urine (due to the physics of that process). For one thing, your body will try to use its existing water supply to flush the extra salt, which means that you'll be urinating (= dehydrating) more than usual. Once that's all gone, and seawater is the sole source for water in your body, your body will no longer be able to produce urine to carry the usual toxins out. Eventually your kidneys will fail. Although in practice, you will feel like a wreck both physically and mentally long before then, and given that people in a situation where they can only drink seawater generally have other dangerous conditions to deal with, these debilitating effects can well kill you before that. This also explains why diluting seawater is potentially viable - so long as you keep the salt concentration below the level your kidneys can handle, you can keep them working normally.
scandox 9y ago
This didn't surprise me so much. In several hot countries I have noted people taking salt to relieve thirst. In Mongolia I drank heavily salted tea (the usual there) all summer and it becomes quite natural. Maybe I'm missing some of the subtleties here?
- Swizec 9y ago
  You'll notice the same behavior from long distance runners, cyclists, hikers, etc. At some point you start feeling dehydration because you're missing electrolytes. If your water intake isn't salted or packed with minerals in some other way, it just makes you thirstier and thirstier. Especially when it's hot out.
  - PKop 9y ago
    This simple lesson was taught to us day one in boot camp when I was in the army, and reiterated constantly over the years. We were required to take our salt packet out of our MRE's and eat the entire contents. The amount of water consumed (and flushed out through perspiration) throughout the day would have severely dehydrated anyone who didn't consume adequate (high) levels of salt.
    - mistermann 9y ago
      I drink tons of water and I get lots of cramps, presumably from electrolyte shortage. Is there any way of knowing what the right amount of salt is to be consuming?
      - sz4kerto 9y ago
        Drink isotonic fluids (one of the best: alcohol-free beer).
        lostlogin 9y ago
        But the very best is beer. Garage Project Garagista more specifically.
dottrap 9y ago
This needs to be paired with Scientific American: It's time to end the war on salt https://www.scientificamerican.com/article/its-time-to-end-the-war-on-salt/ https://www.scientificamerican.com/article/its-time-to-end-t...
- SepUltra 9y ago
  Actually, the Scientific American article is wrong. This space study also concludes that salt is harmful. Now possibly in more ways than was previously known.
  - Retric 9y ago
    Salt intake over years is not the same as salt intake over a month making this study meaningless in terms of long term heath impacts.
    - SepUltra 9y ago
      Nope.
      - Retric 9y ago
        The US recommended salt intake is limited to 1.5g to 2.3g grams of salt depending on some risk factors. Their 'low' intake was 6g and high was 12grams / day. https://sodiumbreakup.heart.org/how_much_sodium_should_i_eat https://sodiumbreakup.heart.org/how_much_sodium_should_i_eat So, I am saying almost 5x the recommended limit for a month might not generalize very well. Sorry, 'Nope' is not going to cut it. Further, the human body climatizes to various situations over time suck as heat or altitude, I suspect salt intake is probably good example of that.
        SepUltra 9y ago
        Nope. Try again. If you bother to read the study, this describes how salt induces breakdown of proteins and carbohydrates in body. That's in addition to other ill effects salt has that we are more aware of.
tetraodonpuffer 9y ago
my n=1: I am on an extremely low sodium diet (around 500mg/day) and I didn't find any difference in thirst or hunger levels compared to when I was on a more typical 4000-5000mg/day one. The only change for me (besides of course a period of adjustment where food didn't taste like much) has been a significantly lower blood pressure (from typically 145/85 to 105/65), everything else has remained pretty much the same.
- cannonpr 9y ago
  That's interesting, did you control for changes in other diet elements, exercise, and water intake ? Some more recent studies show that except for short term spikes in blood pressure, salt isn't that guilty for high blood pressure in healthy individuals.
  - dhimes 9y ago
    I'm going to throw a wrench into the gears by sharing the following: I had high blood pressure- not medication-triggering, just high-eyebrow stuff when I was younger (30s-early 40s). As a teenager I learned of the dangers of salt and weaned it out of my diet. I got married and am the cook of the family, so after much complaining I started to add salt to my dishes when I cooked. My blood pressure when down. Not by a little, but to the "wow your blood pressure is amazing" category (105 or 110). So, yeah, I don't think we know how salt works. NB my exercise/habits stayed pretty much the same in this period.
    - closure 9y ago
      My cardiologist told me never to try a low-sodium diet without talking with him first. He is very up-to-date on research and said that an equal number of people see blood pressure increase on low-sodium as see blood pressure decrease but for many (most?) people the difference is negligible. In other words if you are one of the ones who is very sensitive to changes in sodium you are as likely to be harmed as helped by lowering sodium.
      - 9y ago
vmarsy 9y ago
> Instead of drinking more, the crew were drinking less in the long run when getting more salt. So where was the excreted water coming from? “There was only one way to explain this phenomenon,” Dr. Titze said. “The body most likely had generated or produced water when salt intake was high.” That's odd, what if simply a high-level of sodium reduces your perspiration? Wikipedia[1] says "The volume of water lost in sweat daily is highly variable, ranging from 100 to 8,000 mL/day." so between 0.1 and 8 liters per day! [2] even says 10 to 12 liters per day! If on average over a long period the subjects drank let's say exactly 1 liter per day and peed strictly more than 1 liter of water, then I'd agree with what this Dr. said, but neither this nytimes article, nor the 2 papers mentioned [3][4] mention the word perspiration or sweat in their abstracts/summaries, why not? Off-topic: Did nytimes.com made it hard on purpose to select text from their article? On Chrome and Firefox I can't select text easily, only Edge lets me. [1] https://en.wikipedia.org/wiki/Perspiration https://en.wikipedia.org/wiki/Perspiration [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267797/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267797/ [3] https://www.jci.org/articles/view/88530 https://www.jci.org/articles/view/88530 [4] https://www.jci.org/articles/view/88532 https://www.jci.org/articles/view/88532
- maxerickson 9y ago
  It's not odd though, water is one of the outputs of our energy metabolism.
jrapdx3 9y ago
For the past year I've been on a low sodium diet, not so easy to achieve. After reviewing the renal physiology I learned about years ago re: sodium and calcium regulation, I'll testify it's every bit as complex as I remember and then some. I'll be interested in reading the articles the newspaper report is based on, but ATM not sure how much the new findings contradict (vs. extend) what's thought to be true about the physiological roles of sodium. In terms of implications for health issues, conditions like hypertension are enormously heterogeneous in origin, salt intake being only one factor among a huge number of factors involved. I was interested in the comment that high salt intake was potentially adverse for bone health via glucocorticoid stimulation. One thing I've recently learned is how high dietary sodium negatively affects bone calcium balance via mechanisms within bone cells, and in some people, excessive renal calcium excretion as well. These issues aren't AFAIK primarily mediated by elevated cortisol. So it seems to be suggesting another way high sodium intake promotes bone loss. Goes to show we know a lot less than we think we know, in this case about body regulation of essential minerals like sodium and calcium. When we realize that also applies to every other factor we think related to high blood pressure or osteoporosis, it's very humbling indeed.
- epmaybe 9y ago
  A random theory, if you will: glucocorticoids have a weak affinity for the mineralocorticoid receptors (aldosterone, salt and water retention). The increased salt reabsorption caused by this could cause an osmotic gradient driving calcium excretion. It sounds a bit too complicated though, where a transporter would fit in nicely.
  - jrapdx3 9y ago
    I don't have any direct info re: mineralocorticoid effect on renal reabsorbtion of calcium, however the interaction of sodium and calcium has been studied as it is important in kidney disease, for example kidney stones, and osteoporosis as well. Here is an article on an excellent site that discusses some of the significant aspects of sodium/calcium regulation: http://kidneystones.uchicago.edu/does-too-much-protein-increase-stones-or-damage-bones/ http://kidneystones.uchicago.edu/does-too-much-protein-incre....
runeks 9y ago
I have a hypothesis that all the negative effects associated with increased salt intake are really negative effects of overeating. If we measure the salt intake of people who primarily eat fast food -- which has a constant salt content -- the amount of salt ingested will be proportional to the amount of food ingested. So the person who eats five Big Mac meals a day will ingest, roughly, five times as much salt as a person eating only one, but I would claim the adverse effects associated with this are related to overeating, not the increased salt intake. Is anyone familiar with studies that study the health effects of salt with this in mind? I.e. keeping food amounts constant over different groups, while varying only salt content?
- stinos 9y ago
  all the negative effects associated with increased salt intake are really negative effects of overeating I'd also say that plays a role to some degree in real life, but only some. Net effects of higher salt intake (given oter things remain equal) can exist as well: the article clearly mentions higher salt intake leading to higher glucocorticoid levels which in turn are linked to osteoporosis, muscle loss, type 2 diabetes and other metabolic problems
givan 9y ago
Salt as far as I know is the only mineral (non plant) spice we use, it's purpose is to enhance taste. There is a common confusion between salt (sodium chloride) and sodium, many falsely believing salt is not used only for taste but it's essential for health. Sodium is a vital element that is found in almost all plants and animals and there is no need for an extra sodium intake because our food has plenty. Sodium and potassium balance in the body is essential for cell physiology and our health https://en.wikipedia.org/wiki/Na%2B/K%2B-ATPase https://en.wikipedia.org/wiki/Na%2B/K%2B-ATPase I don't add salt in my food and avoid products with salt for more than a year, "heavy food" doesn't feel as heavy, my skin is not as dry as before and looks better and injuries seem to heal faster.
- vixen99 9y ago
  its purpose
- godmodus 9y ago
  human habits include many activities that consume a lot of water too - if you drink alcohol, salt consumption on that day/night is a must! i find adding some soysauce to a cup of water and chugging that before bed takes care of most side effects. and food does taste better with salt added, i must admit, esp. meat.
  - gosheroo 9y ago
    >food does taste better with salt added Right, so the mode of intake matters, not just the salt itself. For example one could eat bland (unsalted) food and drink salt water later which would produce less pleasure for the same quantity of sodium consumed. So there might be different physiological effects.
    - godmodus 9y ago
      taste + pleasure centers in the brain. used to be useful when we were huntergatherers! these days, it's just nice for food to taste good!
- 9y ago

195 points by mherrmann 9y ago

That is interesting. I see an advantage this adaption offers when trapped with only salty sea water. Excessive salt intake may occur naturally when in the ocean for whatever reason. When this reduces thirst and offers an (internal) alternative for water this may help you survive until you strand somewhere to find fresh water. Not the worst trait evolution could select for.

Freestyler_3 9y ago
There is a negative side to it, you use up more calories. (unrelated, I think fast food companies are already aware of the more hunger from salty food.)

Mz 9y ago

And, Dr. Titze said, high glucocorticoid levels are linked to such conditions as osteoporosis, muscle loss, Type 2 diabetes and other metabolic problems. And cystic fibrosis, which is perhaps best tldr'd as a salt wasting condition, frequently leads to Cystic Fibrosis Related Diabetes, which is neither type 1 nor type 2 diabetes.

carbocation 9y ago
CFTR, being a chloride channel, most likely leads to diabetes as a consequence of its effects on the voltage-regulated insulin release in beta cells from glucose sensing. [1] It strikes me as unlikely to be related to the salt-wasting that occurs from failure to reabsorb chloride in the epithelium. 1 = https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4104438/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4104438/
- Mz 9y ago
  I think it is probably a lot more complicated than that. CF does a great many things to the body. It is an inflammatory condition and I have seen multiple articles linking diabetes and inflammation. People with CF tend to be seriously underweight and I have recently seen articles that link inadequate muscle protein to insulin resistance. There is no doubt more than that going on, those are just a couple of things that occur to me off the top of my head.
  - carbocation 9y ago
    "I think it is probably a lot more complicated than that." That's an evergreen, accurate response to anything in human biology!
    - Mz 9y ago
      So you're saying I'm right! ;-)
  - Steer 9y ago
    It would be nice of you to provide some sources for your claims. I don't know if you are right or not, but at least providing links to the articles you are referring to would be appreciated.
    - Mz 9y ago
      Diabetes and inflammation is actually easily googled, but here is a respectable source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1087185/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1087185/ PDF: The underappreciated role of muscle in health and disease http://ajcn.nutrition.org/content/84/3/475.full.pdf http://ajcn.nutrition.org/content/84/3/475.full.pdf There is a long and wordy section about muscle and insulin resistance, some choice outtakes: However, over the past few years it has become evident that changes in the metabolic function of muscle itself plays a more direct role in the genesis of insulin resistance than previously appreciated. (This is rebutting the idea that higher fat levels explain insulin resistance.) as little as a single bout of exercise [thereby stimulating triacylglycerol deposition in muscle intramuscular triacylglycerol (IMTG) oxidation] can transiently reverse insulin resistance (44). The section concludes with: Regardless of the specific intracellular mechanisms at the molecular level, it is clear that insulin resistance is not simply the result of increased fat mass and release of FFAs into plasma at an accelerated rate, with the muscle responding to elevated plasma FAA concentrations. Rather, alterations in the metabolic function of muscle are central to the development of insulin resistance and ultimately diabetes. I am not finding an exact point at which it explicitly says "Muscle loss causes insulin resistance" but that was my personal takeaway from reading this some time back. (On the other hand, maybe it does explicitly say that and I am just rushed for time and have crap eyesight, so maybe I am just not finding it. Whatever.)

reitanqild 9y ago

I think Thor Heyerdahl or someone on one of his crews noted that when they added seawater to the freshwater to make it last longer it also made them less thirsty. IIRC they thought it was an interesting observation since it was against all common understanding, but I don't think they ever came close to a solution to why.

abovemypaygrade 9y ago
Did he (or they) happen to mention the ratios of salt water to fresh? I don't know a whole lot about this topic, but I do recall reading somewhere that thirsty seafarers who succumbed to the urge to drink seawater ended up dying more quickly. I wonder if they figured out how much was okay to drink before it started negatively impacting health.
- pilsetnieks 9y ago
  The negative impact is due to water loss via vomiting or diarrhea, and thus having a negative water balance. It's not like saltwater in itself kills you. In fact, you could drink the water of some less salty seas, e.g. the Baltic Sea.
  - int_19h 9y ago
    The real bad impact is from disrupting the way your kidneys work. Basically, seawater has a higher concentration of salt than it is possible for your kidneys to remove via urine (due to the physics of that process). For one thing, your body will try to use its existing water supply to flush the extra salt, which means that you'll be urinating (= dehydrating) more than usual. Once that's all gone, and seawater is the sole source for water in your body, your body will no longer be able to produce urine to carry the usual toxins out. Eventually your kidneys will fail. Although in practice, you will feel like a wreck both physically and mentally long before then, and given that people in a situation where they can only drink seawater generally have other dangerous conditions to deal with, these debilitating effects can well kill you before that. This also explains why diluting seawater is potentially viable - so long as you keep the salt concentration below the level your kidneys can handle, you can keep them working normally.

scandox 9y ago

This didn't surprise me so much. In several hot countries I have noted people taking salt to relieve thirst. In Mongolia I drank heavily salted tea (the usual there) all summer and it becomes quite natural. Maybe I'm missing some of the subtleties here?

Swizec 9y ago
You'll notice the same behavior from long distance runners, cyclists, hikers, etc. At some point you start feeling dehydration because you're missing electrolytes. If your water intake isn't salted or packed with minerals in some other way, it just makes you thirstier and thirstier. Especially when it's hot out.
- PKop 9y ago
  This simple lesson was taught to us day one in boot camp when I was in the army, and reiterated constantly over the years. We were required to take our salt packet out of our MRE's and eat the entire contents. The amount of water consumed (and flushed out through perspiration) throughout the day would have severely dehydrated anyone who didn't consume adequate (high) levels of salt.
  - mistermann 9y ago
    I drink tons of water and I get lots of cramps, presumably from electrolyte shortage. Is there any way of knowing what the right amount of salt is to be consuming?
    - sz4kerto 9y ago
      Drink isotonic fluids (one of the best: alcohol-free beer).
      - lostlogin 9y ago
        But the very best is beer. Garage Project Garagista more specifically.

dottrap 9y ago

This needs to be paired with Scientific American: It's time to end the war on salt https://www.scientificamerican.com/article/its-time-to-end-the-war-on-salt/ https://www.scientificamerican.com/article/its-time-to-end-t...

SepUltra 9y ago
Actually, the Scientific American article is wrong. This space study also concludes that salt is harmful. Now possibly in more ways than was previously known.
- Retric 9y ago
  Salt intake over years is not the same as salt intake over a month making this study meaningless in terms of long term heath impacts.
  - SepUltra 9y ago
    Nope.
    - Retric 9y ago
      The US recommended salt intake is limited to 1.5g to 2.3g grams of salt depending on some risk factors. Their 'low' intake was 6g and high was 12grams / day. https://sodiumbreakup.heart.org/how_much_sodium_should_i_eat https://sodiumbreakup.heart.org/how_much_sodium_should_i_eat So, I am saying almost 5x the recommended limit for a month might not generalize very well. Sorry, 'Nope' is not going to cut it. Further, the human body climatizes to various situations over time suck as heat or altitude, I suspect salt intake is probably good example of that.
      - SepUltra 9y ago
        Nope. Try again. If you bother to read the study, this describes how salt induces breakdown of proteins and carbohydrates in body. That's in addition to other ill effects salt has that we are more aware of.

tetraodonpuffer 9y ago

my n=1: I am on an extremely low sodium diet (around 500mg/day) and I didn't find any difference in thirst or hunger levels compared to when I was on a more typical 4000-5000mg/day one. The only change for me (besides of course a period of adjustment where food didn't taste like much) has been a significantly lower blood pressure (from typically 145/85 to 105/65), everything else has remained pretty much the same.

cannonpr 9y ago
That's interesting, did you control for changes in other diet elements, exercise, and water intake ? Some more recent studies show that except for short term spikes in blood pressure, salt isn't that guilty for high blood pressure in healthy individuals.
- dhimes 9y ago
  I'm going to throw a wrench into the gears by sharing the following: I had high blood pressure- not medication-triggering, just high-eyebrow stuff when I was younger (30s-early 40s). As a teenager I learned of the dangers of salt and weaned it out of my diet. I got married and am the cook of the family, so after much complaining I started to add salt to my dishes when I cooked. My blood pressure when down. Not by a little, but to the "wow your blood pressure is amazing" category (105 or 110). So, yeah, I don't think we know how salt works. NB my exercise/habits stayed pretty much the same in this period.
  - closure 9y ago
    My cardiologist told me never to try a low-sodium diet without talking with him first. He is very up-to-date on research and said that an equal number of people see blood pressure increase on low-sodium as see blood pressure decrease but for many (most?) people the difference is negligible. In other words if you are one of the ones who is very sensitive to changes in sodium you are as likely to be harmed as helped by lowering sodium.
    - 9y ago

vmarsy 9y ago

> Instead of drinking more, the crew were drinking less in the long run when getting more salt. So where was the excreted water coming from? “There was only one way to explain this phenomenon,” Dr. Titze said. “The body most likely had generated or produced water when salt intake was high.” That's odd, what if simply a high-level of sodium reduces your perspiration? Wikipedia[1] says "The volume of water lost in sweat daily is highly variable, ranging from 100 to 8,000 mL/day." so between 0.1 and 8 liters per day! [2] even says 10 to 12 liters per day! If on average over a long period the subjects drank let's say exactly 1 liter per day and peed strictly more than 1 liter of water, then I'd agree with what this Dr. said, but neither this nytimes article, nor the 2 papers mentioned [3][4] mention the word perspiration or sweat in their abstracts/summaries, why not? Off-topic: Did nytimes.com made it hard on purpose to select text from their article? On Chrome and Firefox I can't select text easily, only Edge lets me. [1] https://en.wikipedia.org/wiki/Perspiration https://en.wikipedia.org/wiki/Perspiration [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267797/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267797/ [3] https://www.jci.org/articles/view/88530 https://www.jci.org/articles/view/88530 [4] https://www.jci.org/articles/view/88532 https://www.jci.org/articles/view/88532

maxerickson 9y ago
It's not odd though, water is one of the outputs of our energy metabolism.

jrapdx3 9y ago

For the past year I've been on a low sodium diet, not so easy to achieve. After reviewing the renal physiology I learned about years ago re: sodium and calcium regulation, I'll testify it's every bit as complex as I remember and then some. I'll be interested in reading the articles the newspaper report is based on, but ATM not sure how much the new findings contradict (vs. extend) what's thought to be true about the physiological roles of sodium. In terms of implications for health issues, conditions like hypertension are enormously heterogeneous in origin, salt intake being only one factor among a huge number of factors involved. I was interested in the comment that high salt intake was potentially adverse for bone health via glucocorticoid stimulation. One thing I've recently learned is how high dietary sodium negatively affects bone calcium balance via mechanisms within bone cells, and in some people, excessive renal calcium excretion as well. These issues aren't AFAIK primarily mediated by elevated cortisol. So it seems to be suggesting another way high sodium intake promotes bone loss. Goes to show we know a lot less than we think we know, in this case about body regulation of essential minerals like sodium and calcium. When we realize that also applies to every other factor we think related to high blood pressure or osteoporosis, it's very humbling indeed.

epmaybe 9y ago
A random theory, if you will: glucocorticoids have a weak affinity for the mineralocorticoid receptors (aldosterone, salt and water retention). The increased salt reabsorption caused by this could cause an osmotic gradient driving calcium excretion. It sounds a bit too complicated though, where a transporter would fit in nicely.
- jrapdx3 9y ago
  I don't have any direct info re: mineralocorticoid effect on renal reabsorbtion of calcium, however the interaction of sodium and calcium has been studied as it is important in kidney disease, for example kidney stones, and osteoporosis as well. Here is an article on an excellent site that discusses some of the significant aspects of sodium/calcium regulation: http://kidneystones.uchicago.edu/does-too-much-protein-increase-stones-or-damage-bones/ http://kidneystones.uchicago.edu/does-too-much-protein-incre....

runeks 9y ago

I have a hypothesis that all the negative effects associated with increased salt intake are really negative effects of overeating. If we measure the salt intake of people who primarily eat fast food -- which has a constant salt content -- the amount of salt ingested will be proportional to the amount of food ingested. So the person who eats five Big Mac meals a day will ingest, roughly, five times as much salt as a person eating only one, but I would claim the adverse effects associated with this are related to overeating, not the increased salt intake. Is anyone familiar with studies that study the health effects of salt with this in mind? I.e. keeping food amounts constant over different groups, while varying only salt content?

stinos 9y ago
all the negative effects associated with increased salt intake are really negative effects of overeating I'd also say that plays a role to some degree in real life, but only some. Net effects of higher salt intake (given oter things remain equal) can exist as well: the article clearly mentions higher salt intake leading to higher glucocorticoid levels which in turn are linked to osteoporosis, muscle loss, type 2 diabetes and other metabolic problems

givan 9y ago

Salt as far as I know is the only mineral (non plant) spice we use, it's purpose is to enhance taste. There is a common confusion between salt (sodium chloride) and sodium, many falsely believing salt is not used only for taste but it's essential for health. Sodium is a vital element that is found in almost all plants and animals and there is no need for an extra sodium intake because our food has plenty. Sodium and potassium balance in the body is essential for cell physiology and our health https://en.wikipedia.org/wiki/Na%2B/K%2B-ATPase https://en.wikipedia.org/wiki/Na%2B/K%2B-ATPase I don't add salt in my food and avoid products with salt for more than a year, "heavy food" doesn't feel as heavy, my skin is not as dry as before and looks better and injuries seem to heal faster.

vixen99 9y ago
its purpose
godmodus 9y ago
human habits include many activities that consume a lot of water too - if you drink alcohol, salt consumption on that day/night is a must! i find adding some soysauce to a cup of water and chugging that before bed takes care of most side effects. and food does taste better with salt added, i must admit, esp. meat.
- gosheroo 9y ago
  >food does taste better with salt added Right, so the mode of intake matters, not just the salt itself. For example one could eat bland (unsalted) food and drink salt water later which would produce less pleasure for the same quantity of sodium consumed. So there might be different physiological effects.
  - godmodus 9y ago
    taste + pleasure centers in the brain. used to be useful when we were huntergatherers! these days, it's just nice for food to taste good!
9y ago