Drinking seawater

[lewisw]

Lost in a small boat at sea, the body loses salts via sweating and urinating. Logic suggests that these could be replaced by drinking some sea water, perhaps mixed with any fresh that you have, rather than separately. Can anyone suggest how much would be correct, or refute my proposal? Would this also extend supplies? I am not speaking here of drinking nothing but seawater, which is known to be bad.

[RangerXanatos]

Just speculating, I assume you could drink small amounts of seawater mixed with freshwater. Though I would believe that you would get enough from any fish that you caught and ate. As for amounts, I would guess untill the water tasted little less saltier than a tear. I say that because my college chemistry teacher told us that you could make your own eye drop solution from water and salt. To just mix them untill it tasted as a tear. At that point you wouldn't have any difference in osmotic pressure.

I see that this is your first post, why don't you head over to the introductions section and tell us a little about yourself and you experiences.

Daniel

[Jay]

I read some time ago that some studies have been done regarding sea water consumption. Cant find the article. but if memmory servers me, a certain amount of brakish or sea water can be consumed with out harmful effects. Check on the internet. or may be Rick can help you find a link. ( I dont know how he does it ...but he is good at it.)

[Pict]

DON'T DRINK SEAWATER

That said...

In theory the idea goes that you can consume seawater up to the amount that it would take to replace the salts lost due to perspiration. You are talking about a sip or two of water max and most people in boats at sea will get that salt by either taking a mouthful by accident, getting hit in the face by a wave, or just plain licking their dry lips all day. To do those things and also sip at seawater is dangerous IMO.

If you are fortunate enough to get rain it is a good idea to wash your shirt periodically in seawater. As you sit in the raft your seawater soaked shirt will dry but also accumulate salt from spray. Once it is soaked by rainwater the result will actually be saltier than the surrounding seawater and you will have wasted that fresh water. If you rinse out your shirt peridically the total amount of salt will be the same as the seawater and the rain will make it brackish on the first squeeze and start running fresher on the second. It will prevent you from having to wash the salt out of your shirt with fresh rainwater. Mac

[Rick]

Tons of available literature to the contrary, Dr. Bombard actually did just that!

http://en.wikipedia.org/wiki/Alain_Bombard

[crashdive123]

A bit more on consuming salt water - http://en.wikipedia.org/wiki/Sea_water

[lewisw]

The wikipedia reference does not mention sterilisation. I'd have thought that unsterilised diluted seawater would carry a high risk of causing dysentery, and that might be really the most important consideration. And ratios from 2 parts seawater to 3 parts fresh through to 2 parts seawater to 1 part fresh, drunk separately or together, are mentioned. There are also references to quantity limits (like 1 cup per day). This is all really too vague surely?

[Rick]

I'm not aware of any studies (aside from those mentioned in the links above) regarding survival and sea water. Conventional wisdom says not to drink it and in lieu of responsible evidence to the contrary I would be hesitant to bet my life on it. I'll stick with fresh water for my needs.

[crashdive123]

Lewisw - In my over 20 years in the Navy, we discussed open ocean survival a bit. The question often came up about drinking seawater. The answer was universily the same - don't do it. In an open ocean survival situation the big concern is dehydration, not salt loss. You will, in the course of your daily activities at sea be ingesting enough (probably more than you will care to) salt. Getting fresh water through rainwater collection, solar stills, or fish will be of much greater concern. Remember that salt will speed up dehydration - that's why it is such a good preservative.

[tacmedic]

To go along with crashdive's post, the saltwater will increase the dehydration and make you feel more and more thirsty and could trick your brain into drinking more and more seawater when you shouldn't be.

[lewisw]

Now how about this logic: Apparently strong urine contains 22g/litre of salt, and sea water contains 35g/l. Take in no salt and you cease to urinate to retain salt - that's bad, as wastes accumulate in the blood. Drink a litre of seawater and you will pee about 1.5 liters of urine to lose the salt (in the end), taking precious water with the salt, also bad. To maintain a correct minimum urine volume of maybe 1 litre per day (I have read elsewhere), you should therefor take in 22g of salt which might come in about 600ml of seawater (1 pint or so), or from somewhere else, as crashdive has suggested.

So that means the right thing to do is all about urine volume - you only drink some seawater if you have stopped peeing, otherwise you're getting enough salt from somewhere else. You only drink just a little seawater even then, because it will cause you too pee more than you've drunk, and lose water overall.

[Rick]

I guess I have to say yes to your question because you need input and output to stay healthy. However, I think you might have the wrong idea about salt needs. Let's assume some theoretical model in which you have no salt intake but you do have water intake. You are still going to produce urine (re:"Take in no salt and you cease to urinate to retain salt") You body will still expel excess water, other metabolic wastes and organic materials. Even if you expelled no salt in our model.

The real concern with salt water ingestion is the reaction at the cellular level. Once the cells begin to lose water you start to dehydrate (duh!). Given enough time, that plays havoc on both cognitive ability and the body's ability to regulate things like heartbeat.

Someone else on here offered a great saying. "If urine is clear, have no fear. If urine is yellow you're a hurting fellow." That's a great rule of thumb to remember how much water your body needs. Urine should flow clear.

[crashdive123]

Lewisw - I gotta disagree with you on drinking salt water if you stop urinating. If you have stopped urinating you have already begun dehydrating. By ingesting salt water you will speed up that process.

[RobertRogers]

Don't do it!!!

The small amount of gain you MIGHT get is far offset by the danger of becoming more dehydrated.

I have spoken.

[trax]

uh yeah, what double R said, jeez....

[Sarge47]

Yo Lewisw, DON'T EVER DRINK SEAWATER!!!!!:mad: Not without distilling it 1st. There are many stories of the madness it's caused as a result! In one case, two people became shark food because they hallucinated as a result & got out of their liferaft to swim over to the parking lot to get their car...problem was they were lost at sea miles away from any landfall. Also forget the urine, dude, sheesh, you been watching to much "Man vs Wild"!:rolleyes:

[Pict]

Dehydration progresses from the blood to the cells of the body. As the water level in the blood is lost it robs water from the cells to bring itself back into operatonal range. When you drink excessive salt, water leaves the blood to dilute the salt in the digestive system to bring it to the same salinity as the body so it can pass out of the system. Once the excess salt is eliminated by the kidneys the blood will trigger your thirst mechanism saying "get me back to normal". Failing that the blood will take water from body cells to continue "being blood". Cellular dehydration takes much longer to recover from than blood dehydration. People who's blood is dehydrated respond to drinking oral rehydration solutions. People whose body tissues have become dehydrated typically need IV's.

Oral Rehydration Solution. This should be at body temperature not cold.

1 liter of clean water
1/4 tsp table salt
1/4 tsp sodium bicarbonate (if you don´t have this double the salt to 1/2 tsp)
2 Tbs sugar or honey

If you look at the amount of salt in this solution you see that it is far less salty than seawater which typically has about 35+/- grams of salt per liter, or about what would fit in a small salt shaker.
Mac

[Pict]

Human consumption of seawater

Accidentally consuming small quantities of clean seawater is not harmful, especially if the seawater is consumed along with a larger quantity of fresh water. However, consuming seawater to maintain hydration is counterproductive; in the long run, more water must be expended to eliminate the seawater's salt (through excretion in urine) than the amount of water that is gained from drinking the seawater itself. [7]

This occurs because the amount of sodium chloride in human blood is actively regulated within a very narrow range of 9 g/L (0.9% by weight) by the kidney. Drinking seawater (which contains about 3.5% ions of dissolved sodium chloride) temporarily increases the concentration of sodium chloride in the blood. This in turn promotes sodium excretion by the kidney, but the sodium concentration of seawater is above the maximum concentrating ability of the human kidney. Eventually with further seawater intake the blood concentration of sodium will rise to toxic levels, removing water from all cells and interfering with nerve conduction ultimately giving seizures and heart arrhythmias which become fatal.

Of note, various animals adapt to harsh living conditions. For example, the desert rat is able to concentrate sodium far more efficiently than the human kidney, and therefore would be able to survive by drinking seawater.

Survival manuals consistently advise against drinking seawater. For example, the book "Medical Aspects of Harsh Environments" (Chapter 29 - Shipboard Medicine) [1] presents a summary of 163 life raft voyages. The risk of death was 39% for those who drank seawater, compared to only 3% for those who did not drink seawater.

http://en.wikipedia.org/wiki/Sea_water

[Rick]

I read quite some time ago about a re-hydration recipe that was being taught in the third world as a first aid for diarrhea, which can easily lead to dehydration. Since most in the 3rd world doesn't have measuring devices the recipe was:

1 liter of water
1 fist of molasses (sugar)
1 pinch of salt

Which is close to what Mac posted above.

[lewisw]

It seems as though 'oral rehydration salts' apply to medical dehydration caused by diarrhoea, rather than natural dehydration caused by lack of fresh water - and even then the amount of salt is tiny, and the solution is mostly sugar. So I suppose the question is: Should any salt be taken at all with natural dehydration? If not then the people who drank even a little seawater, or like Thor Heyerdahl, a seawater freshwater mix, did themselves no good at all, or even some harm. According to these arguments the seawater they drank, mixed or not, caused a greater loss of body water in the end. So is the obvious dead right: Any source of salt is bad for you when you're thirsty? But then again I do know that I sometimes deliberately take salt when I've had a lot of exercise in hot weather...

[Rick]

I don't take any form of additional salt. I think there is more than enough in packaged foods to take care of us several times over. I've spent a lot of time out in the sun working in some pretty hot weather and as long as I kept water handy I never had a problem.

[crashdive123]

Some people will take salt tablets when they are doing a lot of physical activity in higher temps. For some it may help prevent cramping. If you use any kind of sports drink (gatorade, powerade) they contain salt as well as other essential minerals and electrolytes to help the body reover. For most people there is enough salt naturally occuring in their diets that they shouldn't need salt suplements. Remember that if you are just exercising in hot weather, and not stranded at sea in a raft, obtaining water is probably not a primary concern as we started talking about in this thread.

[trax]

For a brief stint, in my youth, I worked in a copper smelter, two 10,000 ton furnaces, average temperature when working within 15 feet of the furnaces 125 F. I used salt tablets but very sparingly, some guys that had been there for quite some time popped them like candy. I'm pretty sure that extended use over a long period was doing things to mess up their physiology.

[lewisw]

I was trying to think of what you would mix with seawater to make a rehydration drink, if that's what's needed. In the absence of a packet of sugar on an open boat, I worked out that the ingredients (salt, natural sugar) in rehydration salts look very like those in any soft drink (orangeade, coke,pepsi, lucosade etc etc, maybe even beer!). Any comments?

[crashdive123]

Not sure why you continue to ask about making a drink with seawater (unless you're working on marketing some sort of product). Most people that have responded to your question about drinking seawater have responded with a "don't do it" kind of answer. Is there some more background that you could provide that may help us help you?

[Rick]

Not anywhere near the same percentage of salt. The ocean is about 3.5%, or 35 parts per thousand.

[trax]

....Any comments?

yeah, give it up.

[Pict]

Lewis,

Oral Rehydration Solution. This should be at body temperature not cold.

1 liter of clean water
1/4 tsp table salt
1/4 tsp sodium bicarbonate (if you don´t have this double the salt to 1/2 tsp)
2 Tbs sugar or honey

This information was taken from the book "Where There is No Doctor" and applies to humans who are dehydrated from whatever means, sweat or running out the end. I have used this mix for people suffering from dehydration caused by heat as well as illness.

The small amount of salt and larger amount of sugar speed up the rehydration process. When you sweat you lose electrolytes and they need to be put back in. The amount of salt lost is small, 1/4 to 1/2 TEASPOON per LITER of water, about 1.5 to 3 grams of salt.

The amount of salt in a liter of seawater is about 35 grams or 7.4 teaspoons of salt, enough to make about 17 liters at 1/2 tsp, or 23 liters at 1/4, of oral rehydration drink when mixed with fresh water.

To use some seawater as the salt portion of one liter of rehydration mix you would only need about 40 ml or seawater mixed with 960 ml of fresh water and 2 tablespoons of sugar. If you were to use straight seawater you are mixing it with about 23x the amount of salt recommended. The principle ingredient you will need for mixing it is about a 9.5 to 1 ratio of fresh water to salt water. Mac

[Rick]

Either that or the amount of water you're going to drink is huge. By the way, don't do that before going to bed.

[trax]

Either that or the amount of water you're going to drink is huge. By the way, don't do that before going to bed.

Or you could be like the old Indian who drowned in his own teepee. :D

[Gray Wolf]

yeah, give it up.

trax, don't hold back, tell him how you really feel...

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[yellowcab]

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