Dehydration and salt

[Shasta_man]

I have problems with dehydration when I travel on dive vacations. I'm trying to understand how the body manages hydration and the role salt plays in it. Trying to understand how to change my body to hold more water so I'm not so easily dehydrated. I suspect that the amount of salt may have something to do with managing my hydration.

My home climate is pretty darn dry but moving around normally doesn't have any problems. However, very humid places or when I'm deprived of water for some time, it seems easy to push me over the edge. Go from feeling fine to feeling pretty terrible within about 5 minutes. Get very nauseous, maybe like I want to vomit, drained energy, headache, just want to close my eyes and just deal. Drink water and just as quickly, it mostly goes away.

Problem seems to stem from my body keeping very little water and just dumps "extra". I've been trying to up water intake to get body to keep more but it hasn't seemed to help much. For example, spent last 14 hour flight to Asia drinking before leaving, still getting very dehydrated, then about every hour during the flight cycling through drinking lots of water, then in the restroom putting it out, then dehydration, drinking water, out it goes again, repeat. My body ought to be able to balance it better.

Wondering whether lack of salt in my diet might be contributing. Perhaps I actually need more salt to retain water? I eat mostly fresh foods, have a decent diet though not perfect, and don't salt anything. So no salt from preprocessed food.

Thoughts?

 

[Doc Harry]

Without knowing your past medical history it would difficult for anyone to recommend that you increase your intake of salt.

Salt is very important in maintaining hydration. Infact, the World Health Organization's Oral Rehydration Solution (ORS) contains a special formulation of water, sugar and salt for maximal rehydration.

Your body senses your total vascular volume and the concentration (osmolarity) of the vascular volume. Your body then makes adjustments to salt and water absorption and excretion to maintain proper homeostasis. For instance, if the osmolarity increases (i.e., your blood becomes more concentrated) you get a sensation of thirst and drink more water to dilute the solutes. Your kidneys also excrete less water, also serving to dilute the solutes. There are very complex hormonal and neurological mechanisms to maintain water homeostasis, far too complex to try to explain here.

I make some brief calculations years ago to compare the WHO ORS and "sports drinks" such as Gatorade. What I discovered was that Gatorade diluted 50:50 with water grossly approximated the WHO ORS, except that even this dilute Gatorade still had too much sugar. It was easier for me to just dilute Gatorade than to try to measure out sugar and salt into a container according to the WHO ORS formula. Besides, Gatorade tastes a whole lot better than the WHO ORS.

From my personal experience, I really like Gatorade, which is a combination of water, salt and sugar. I work very long hours inside air-conditioned hospitals and get very dehydrated. I can drink a lot of water, but that just makes me pee a lot and I'm still thirsty. However, when I start drinking a dilute 50:50 Gatorade my thirst is quenched and I stay hydrated. That's just my personal experience. You've got to watch the calories, a bottle of Gatorade has about the same calories as a candy bar.

If you are sweating a lot, you are losing a lot of salt and you've got to repalce those losses. Back in the 1970s we used to take a salt tablet (NaCl) every morning with a liter of water to help us keep hydrated when we were outside all day.

It's best to not try to screw with Mother Nature too much. In other words, do not think that if drinking 1 liter is good that 10 liters is better. If drinking one liter quenches your thirst, then don't try to drink 5 more liters.

I think a good rule of thumb is to drink frequently to keep away the thirst, try to keep your pee a very dilute yellow color (but not totally clear like water) and throw a little salt on your food in proportion to the amount of salt that you're losing in your sweat.

 

[TSandM]

It's a very good question you are asking.

Salt and water are intimately related in the body. Salt is used to regulate total body liquid VOLUME, and water is used to regulate total body salt concentration. The mechanisms that retain salt, and that retain water, are different, although they both take place in the kidney. They are regulated by different receptors (not in the kidney) which measure either volume or concentration.

In the short term, if you want to expand intravascular and extracellular volume, taking both salt and water will do it that nicely. The salt causes the body to stop excreting water, so as not to get too salty, and the extra water is kept in the body until the salt is diluted appropriately. A few salty crackers just before getting in the water, for example, can minimize the immersion diuresis phenomenon.

If you are sweating, and consume water, the body will let go of a lot of it, so as not to become too dilute. If you consume water faster than the body can excrete it, you can get overdiluted, and end up with muscle cramps or confusion or dizziness.

So, for a normal, healthy person, to be best volume expanded, a small intake of salt and a large intake of liquid is the best balance. This is NOT true for people with significant high blood pressure or other problems requiring a water pill. Such people should NOT try to augment their total volume, or consume significant extra salt.

But there was a time when folks ate salt pills if they thought they were sweating, and those were massive oversupplies of salt. There, you could end up losing a lot of water and replacing it with salt, and getting overconcentrated. Sweat is actually fairly dilute, and your primary need when sweating heavily is still water.

 

[DandyDon]

Wondering whether lack of salt in my diet might be contributing. Perhaps I actually need more salt to retain water? I eat mostly fresh foods, have a decent diet though not perfect, and don't salt anything. So no salt from preprocessed food.

Thoughts?

When I'm working outdoors in the Texas heat or on a dive trip, I increase my salt intake and my normal is above yours. I've had city dwellers visit me at times, just riding around the pickup to watch me work but end up with heat exhaustion even leading to nausea which seemed to be a combination of ladies limiting their liquid intake so as to not need to pee in the field and low salt diets.

Do note that I have zero medical training or credentials. Just posting as an outdoorsman with some observations about urban dwellers.