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I know that sodium deficiency can be deadly. But why is it deadly? Is it because of your muscles getting so rigid that you can't get something with salt in it? Is it because of your brain not able to send signals? Is it because of excess urination to try to get the sodium levels right? Is it because of anemia leaving red blood cell ghosts(the membranes of rbcs) in your bloodstream? Is it a combination of all these factors?

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    $\begingroup$ Can you define "sodium deficiency"? Hyponatremia (not enough sodium in the blood) is usually not caused by insufficient sodium intake. If you eat, you'll get enough sodium. $\endgroup$ – anongoodnurse Dec 14 '15 at 0:14
  • $\begingroup$ As @anongoodnurse said hyponatremia causes a lot of very bad things to happen to the human body. Also, as anongoodnurse said, I have never heard of it from lack of consumption. I have only heard of it when people have consumed too much water causing electrolyte imbalance and is basically just a function of osmosis. Remember that cells have aquaporins, so water is exchanged freely. This seems to be an issue during marathons. Now not consuming enough iodine can be a problem, but that is different than hyponatremia. $\endgroup$ – AMR Dec 14 '15 at 0:57
  • $\begingroup$ I mean too little sodium in the whole body when I say sodium deficiency. In other words not only is the blood affected but everything else that needs sodium(muscles, neurons, blood cells(leading to anemia), and kidneys(leading to dehydration) just to name a few. I don't mean too much water intake(mild water toxicity) $\endgroup$ – Caters Dec 14 '15 at 1:31
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    $\begingroup$ What you are suggesting pretty much will not happen. Because of osmoregulation, your kidneys recirculates the sodium to keep levels constant. It is only in cases of extremes such as water poisoning, extreme exertion, or severe gastric distress that fatal electrolyte imbalance results. On average a serving of rice and fish will give you about 410mg of sodium (a typical meal for large portions of the world). The RDA in the US is no greater than 2300mg per day, but that is the upper limit. An average serving of vegetables gives 32mg, so as @anongoodnurse said if you eat, you'll get enough. $\endgroup$ – AMR Dec 14 '15 at 5:50
  • $\begingroup$ But if, for arguments sake, you could have too little salt, then the result would likely be exactly the same as death by hypernatremia or cholera. $\endgroup$ – AMR Dec 14 '15 at 5:53
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Part of this depends on the exact nature of "salt depletion" you're referring to. I have never actually heard of a case of hyponatremia being caused by low consumption of salt. We don't need to consume NaCl. It's present in the foods we eat in adequate amounts. We may want to salt our food, but it's not necessary for life.

Hyponatremia is an electrolyte imbalance, be it due to excess intake of H2O, inappropriate H2O retention, excess Na+ loss, hyperglygemia or other osmotic force, or other cause. For ease of explanation, I'll address acute hyponatremia, as it leads to death more rapidly. Hyponatremia kills because of the difference in the concentration of sodium across cell membranes.

Normal serum Sodium (Na+) is ~140mEq/L. Acute severe hyponatremia occurs when serum Na+ falls rapidly below 120 mEq/l (some authors use 125mEq/L) in less than 48 hours.

Water accounts for 60% of total body weight, with approximately two-thirds being intracellular and one-third extracellular; of that extracellular water, ~75% is in the fluid between/surrounding cells, and 25% is in blood vessels. Distribution of water/Na+ throughout the body is very tightly regulated.

When serum sodium falls too low, free water moves from areas of lower concentration to higher (into the cells). Tissue becomes edematous. While this isn't a great problem for some tissues, it is for the brain.

The brain is enclosed in a rigid compartment (the skull) with a small amount of fluid (cerebrospinal fluid, or CSF) surrounding it. Inferiorly, there is an small opening called the foramen magmun, where the brainstem leads to the spinal cord.

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When water moves from the blood into the cells of the brain attempting to establish osmotic equilibrium, the brain compensates for the increase in volume by forcing CSF out. This buys some time, but not enough; there is headache and nausea. As the brain continues to expand, intercellular fluid is forced out into CSF (which is being displaced by the brain.) This causes hyperexcitability which leads to seizures. In the meantime, astrocytes swell. Blood flow to the brain is reduced because of increased intracranial pressure, which further damages the cells, increases cellular edema and coma ensues.

If this isn't bad enough (it is; it's an almost irreparable cascade of events), the edema can actually "push" the lower part of the brain down through the foramen magnum resulting in brain stem compression and respiratory arrest. At this point, few people make it back intact with even the best help.

You say,

Basically with too little sodium, it goes from bad to worse until the heart and lungs are affected and the person dies.

Not really. In acute hyponatremia, the brain goes before the rest. Once the brain goes, so follows the body.

in layman's terms
not layman's terms but still easily understandable

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  • $\begingroup$ It is a big problem for the rbcs as well. Water rushes into the rbcs and they burst leaving behind their cell membranes. This helps balance the sodium levels but it leads to anemia. Anemia then leads to less oxygen transport. Less oxygen transport leads to faster heart rate. This eventually isn't enough to raise oxygen transport because it makes atherosclerosis related heart problems more likely and widespread. $\endgroup$ – Caters Dec 14 '15 at 7:34
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    $\begingroup$ Um... no. I don't think you're prioritizing the effects of hyponatremia. Hemolysis isn't one of the major players in morbidity and mortality from hyponatremia. The red blood cells have leeway. The brain does not. If you already have strong opinions about all this stuff, why are you asking this question? $\endgroup$ – anongoodnurse Dec 14 '15 at 8:51
  • $\begingroup$ I am talking about chronic here, not acute. In chronic sodium deficiency it is mainly urination, blood, and the heart and lungs that are affected as well as neurons and muscles $\endgroup$ – Caters Dec 14 '15 at 9:22
  • $\begingroup$ @Caters- I really think you should post your own answer with references. I'm always up for learning new stuff! $\endgroup$ – anongoodnurse Dec 14 '15 at 23:15

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