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>>How could something as simple as salt stymie scientists for so long? The human body has numerous overlapping pathways for salt regulation. Salt (sodium chlor

>>How could something as simple as salt stymie scientists for so long? The human body has numerous overlapping pathways for salt regulation. Salt (sodium chloride) plays a major role in the osmolality (electrolyte concentration) of blood. A drop in the sodium concentration results in the release of renin, which causes changes in vascular constriction, sympathetic activity, and sodium reabsorption itself. This seems like a great research question for systems biology, although it would require some detailed modeling.

userbinator 12y ago
Indeed there are many feedback loops that regulate various things in the body, so I think the general idea is that anything within the range the regulator can compensate for won't cause any immediately harmful effects. On the other hand, making these regulators work constantly near one end of their input range could have long-term effects.
s_q_b 12y ago
Electrolyte balance in general seems like a good research question. We load our food with sodium chloride, but natural diets are far higher in potassium chloride. The relationship between the various electrolytes is something about which we know very little.
- logfromblammo 12y ago
  The function of the various proteins used in the sodium-potassium pump, which transports Na+ out of cells and K+ into cells, against their natural diffusion gradient, suggests that the ratio between Na+ ions and K+ ions in the diet, and their relative concentrations in intercellular fluid is far more important than the absolute quantity you consume. If your Na+ to K+ balance is healthy, consuming too much of both could be solved as easily as drinking more water. But consuming too little of either one will cause the sodium-potassium pumps to function poorly. My hypothesis is that there is an optimal ratio of Na+ to K+ such that the saltiest water (containing only NaCl and KCl) that a human could drink for prolonged periods without observable ill effects has that ratio. A different ratio would require more water for the kidneys to clear the ions present in excess, and that would lower the total concentration of dissolved salts. Learning that value could possibly enable the production of drinkable water by partial desalination with potassium supplementation rather than complete desalination. I have heard that water that is 40% seawater and 60% freshwater can sustain someone in a survival emergency. Perhaps 50% seawater and 50% dilute potassium chloride solution could extend the water supply on a life raft by another 20%? You could hardly do the experiment if an ethical monitor for human experimentation thinks that supplying that much of an absolute quantity of dietary sodium is dangerous, independent of relative concentrations.
  - s_q_b 12y ago
    Instinctually, I'd be a little wary of that, because Na+ and Ka+ do more than act as ions within the neurological system. I'm not sure a higher concentration, even at the right relative concentrations, wouldn't have adverse effects.
    - logfromblammo 12y ago
      It's a bit difficult to figure out the highest concentration that doesn't have adverse effects if you're not allowed to produce adverse effects.
      - s_q_b 12y ago
        We could probably do this with an animal model for testing, and work up to human subjects pretty quickly.

userbinator 12y ago

Indeed there are many feedback loops that regulate various things in the body, so I think the general idea is that anything within the range the regulator can compensate for won't cause any immediately harmful effects. On the other hand, making these regulators work constantly near one end of their input range could have long-term effects.

s_q_b 12y ago

Electrolyte balance in general seems like a good research question. We load our food with sodium chloride, but natural diets are far higher in potassium chloride. The relationship between the various electrolytes is something about which we know very little.

logfromblammo 12y ago
The function of the various proteins used in the sodium-potassium pump, which transports Na+ out of cells and K+ into cells, against their natural diffusion gradient, suggests that the ratio between Na+ ions and K+ ions in the diet, and their relative concentrations in intercellular fluid is far more important than the absolute quantity you consume. If your Na+ to K+ balance is healthy, consuming too much of both could be solved as easily as drinking more water. But consuming too little of either one will cause the sodium-potassium pumps to function poorly. My hypothesis is that there is an optimal ratio of Na+ to K+ such that the saltiest water (containing only NaCl and KCl) that a human could drink for prolonged periods without observable ill effects has that ratio. A different ratio would require more water for the kidneys to clear the ions present in excess, and that would lower the total concentration of dissolved salts. Learning that value could possibly enable the production of drinkable water by partial desalination with potassium supplementation rather than complete desalination. I have heard that water that is 40% seawater and 60% freshwater can sustain someone in a survival emergency. Perhaps 50% seawater and 50% dilute potassium chloride solution could extend the water supply on a life raft by another 20%? You could hardly do the experiment if an ethical monitor for human experimentation thinks that supplying that much of an absolute quantity of dietary sodium is dangerous, independent of relative concentrations.
- s_q_b 12y ago
  Instinctually, I'd be a little wary of that, because Na+ and Ka+ do more than act as ions within the neurological system. I'm not sure a higher concentration, even at the right relative concentrations, wouldn't have adverse effects.
  - logfromblammo 12y ago
    It's a bit difficult to figure out the highest concentration that doesn't have adverse effects if you're not allowed to produce adverse effects.
    - s_q_b 12y ago
      We could probably do this with an animal model for testing, and work up to human subjects pretty quickly.