I have often heard that in terms of hydration there’s no benefit in drinking seawater because it makes the kidneys pump more water out of the body than you’re putting. Seawater contains about 30000 mg/L of dissolved electrolytes.
Some sports drinks contain 1500 mg/L of dissolved electrolytes and are useful for hydration.
So where is the cutoff in salinity beyond which drinking no longer hydrates?
Dunno. I think you might need to split it between dissolved salt (chloride and sodium), and others.
if it’s more concentrated than your urine then you’re fkd is the short
One of the survival-at-sea things that they teach is that there is NO safe amount of sea water that you can drink.
There’s more on drinking sea water (and why you shouldn’t) here:
https://outdoors.stackexchange.com/questions/9920/how-much-sea-water-can-i-safely-drink
I think there was a trial done by the SAS or one of those and found you could survive on small amounts of sea water for a while. Dont remember the details.
SCIENCE said:
if it’s more concentrated than your urine then you’re fkd is the short
So various resources seem to indicate that maximum urine salinity is something like 300 mEq/L, which is ~ 17000 mg/L so I suppose the answer is a bit less than that. Cheers.
captain_spalding said:
One of the survival-at-sea things that they teach is that there is NO safe amount of sea water that you can drink.There’s more on drinking sea water (and why you shouldn’t) here:
https://outdoors.stackexchange.com/questions/9920/how-much-sea-water-can-i-safely-drink
Yeah but I’m not asking about the amount of seawater you can drink. I’m asking about the most saline fluid that, in terms of hydration, you can sensibly drink.
dv said:
I have often heard that in terms of hydration there’s no benefit in drinking seawater because it makes the kidneys pump more water out of the body than you’re putting. Seawater contains about 30000 mg/L of dissolved electrolytes.Some sports drinks contain 1500 mg/L of dissolved electrolytes and are useful for hydration.
So where is the cutoff in salinity beyond which drinking no longer hydrates?
For prolonged periods, the cut-off should be equal to the salinity of sweat. 1 mg sodium = 2.5 mg total electrolytes, approximately.
I’ve just found out that it differs between summer and winter, and between athletes.
“Sweat typically contains 40-60 mmol/L of sodium”. That’s 920 to 1380 mg/L
“Sweat sodium concentrations in summer were less than in winter, the mean value for summer being 44.7 mmol.L-1 and winter 63.8 mmol.L-1.” That’s 1030 mg/L in summer and 1470 mg/L in winter.
“We’ve tested athletes who lose less than 200mg of sodium per litre of sweat and we’ve also seen athletes losing well over 2,300mg per litre”.
“Sweat sodium concentration varies dramatically between individuals, from 250 mg/L to 3000 mg/L”
mollwollfumble said:
dv said:
I have often heard that in terms of hydration there’s no benefit in drinking seawater because it makes the kidneys pump more water out of the body than you’re putting. Seawater contains about 30000 mg/L of dissolved electrolytes.Some sports drinks contain 1500 mg/L of dissolved electrolytes and are useful for hydration.
So where is the cutoff in salinity beyond which drinking no longer hydrates?
For prolonged periods, the cut-off should be equal to the salinity of sweat. 1 mg sodium = 2.5 mg total electrolytes, approximately.
I’ve just found out that it differs between summer and winter, and between athletes.
“Sweat typically contains 40-60 mmol/L of sodium”. That’s 920 to 1380 mg/L
“Sweat sodium concentrations in summer were less than in winter, the mean value for summer being 44.7 mmol.L-1 and winter 63.8 mmol.L-1.” That’s 1030 mg/L in summer and 1470 mg/L in winter.
“We’ve tested athletes who lose less than 200mg of sodium per litre of sweat and we’ve also seen athletes losing well over 2,300mg per litre”.
“Sweat sodium concentration varies dramatically between individuals, from 250 mg/L to 3000 mg/L”
In other words, definitely not more than 7500 mg/L electrolytes, and that’s the extreme long term limit.
For some people, the long term limit could be as low as 500 mg/L electrolytes.
mollwollfumble said:
mollwollfumble said:
dv said:
I have often heard that in terms of hydration there’s no benefit in drinking seawater because it makes the kidneys pump more water out of the body than you’re putting. Seawater contains about 30000 mg/L of dissolved electrolytes.Some sports drinks contain 1500 mg/L of dissolved electrolytes and are useful for hydration.
So where is the cutoff in salinity beyond which drinking no longer hydrates?
For prolonged periods, the cut-off should be equal to the salinity of sweat. 1 mg sodium = 2.5 mg total electrolytes, approximately.
I’ve just found out that it differs between summer and winter, and between athletes.
“Sweat typically contains 40-60 mmol/L of sodium”. That’s 920 to 1380 mg/L
“Sweat sodium concentrations in summer were less than in winter, the mean value for summer being 44.7 mmol.L-1 and winter 63.8 mmol.L-1.” That’s 1030 mg/L in summer and 1470 mg/L in winter.
“We’ve tested athletes who lose less than 200mg of sodium per litre of sweat and we’ve also seen athletes losing well over 2,300mg per litre”.
“Sweat sodium concentration varies dramatically between individuals, from 250 mg/L to 3000 mg/L”
In other words, definitely not more than 7500 mg/L electrolytes, and that’s the extreme long term limit.
For some people, the long term limit could be as low as 500 mg/L electrolytes.
Cheers
dv said:
mollwollfumble said:In other words, definitely not more than 7500 mg/L electrolytes, and that’s the extreme long term limit.
For some people, the long term limit could be as low as 500 mg/L electrolytes.
Cheers
In other other words, for short term and possible long term, dilute seawater 1 in 10 and possibly 1 in 5.
Are you aware of the voyage of Bligh after the Mutiny on the Bounty?
Bligh was set adrift without anywhere near sufficient fresh water in his longboat. It was essentially a murder.
This is a really hot climate. Bligh had his rowers continually douse their clothes and themselves in salt water to reduce evaporation and sweating to a minimum. By reducing the intake of drinking water to all the men he managed to get them all alive to a place where fresh water was available.
After Bligh reached England in April 1790, the Admiralty despatched HMS Pandora to apprehend the mutineers. Fourteen were captured in Tahiti and imprisoned on board Pandora, which then searched without success for Christian’s party that had hidden on Pitcairn Island. After turning back towards England, Pandora ran aground on the Great Barrier Reef, with the loss of 31 crew and four prisoners from Bounty. The ten surviving detainees reached England in June 1792 and were court-martialled; four were acquitted, three were pardoned, and three were hanged
——
Given the cost of these journeys and the risk to life, it seems ridiculous to send a ship to the other side of the world to capture mutineers.
dv said:
After Bligh reached England in April 1790, the Admiralty despatched HMS Pandora to apprehend the mutineers. Fourteen were captured in Tahiti and imprisoned on board Pandora, which then searched without success for Christian’s party that had hidden on Pitcairn Island. After turning back towards England, Pandora ran aground on the Great Barrier Reef, with the loss of 31 crew and four prisoners from Bounty. The ten surviving detainees reached England in June 1792 and were court-martialled; four were acquitted, three were pardoned, and three were hanged
——
Given the cost of these journeys and the risk to life, it seems ridiculous to send a ship to the other side of the world to capture mutineers.
Law And Order
dv said:
After Bligh reached England in April 1790, the Admiralty despatched HMS Pandora to apprehend the mutineers. Fourteen were captured in Tahiti and imprisoned on board Pandora, which then searched without success for Christian’s party that had hidden on Pitcairn Island. After turning back towards England, Pandora ran aground on the Great Barrier Reef, with the loss of 31 crew and four prisoners from Bounty. The ten surviving detainees reached England in June 1792 and were court-martialled; four were acquitted, three were pardoned, and three were hanged——
Given the cost of these journeys and the risk to life, it seems ridiculous to send a ship to the other side of the world to capture mutineers.
A warning to others.
Let’s go to the tape.
Potential Mutineer 1-: You know if we get a few of the lads together, knock the captain and 1st mate on the head and sail to a remote island we could lead the life of riley.
PM 2-: Not on your nelly, they’ll hunt us down and hang us.
dv said:
After Bligh reached England in April 1790, the Admiralty despatched HMS Pandora to apprehend the mutineers. Fourteen were captured in Tahiti and imprisoned on board Pandora, which then searched without success for Christian’s party that had hidden on Pitcairn Island. After turning back towards England, Pandora ran aground on the Great Barrier Reef, with the loss of 31 crew and four prisoners from Bounty. The ten surviving detainees reached England in June 1792 and were court-martialled; four were acquitted, three were pardoned, and three were hanged——
Given the cost of these journeys and the risk to life, it seems ridiculous to send a ship to the other side of the world to capture mutineers.
Bounty was refitted under Banks’s supervision at Deptford Dockyard on the River Thames. The great cabin, normally the ship’s captain’s quarters, was converted into a greenhouse for over a thousand potted breadfruit plants, with glazed windows, skylights, and a lead-covered deck and drainage system to prevent the waste of fresh water. The space required for these arrangements in the small ship meant that the crew and officers would endure severe overcrowding for the duration of the long voyage.
That’s interesting to imagine.
dv said:
After Bligh reached England in April 1790, the Admiralty despatched HMS Pandora to apprehend the mutineers. Fourteen were captured in Tahiti and imprisoned on board Pandora, which then searched without success for Christian’s party that had hidden on Pitcairn Island. After turning back towards England, Pandora ran aground on the Great Barrier Reef, with the loss of 31 crew and four prisoners from Bounty. The ten surviving detainees reached England in June 1792 and were court-martialled; four were acquitted, three were pardoned, and three were hanged——
Given the cost of these journeys and the risk to life, it seems ridiculous to send a ship to the other side of the world to capture mutineers.
That’s how they ran the empire.
Peak Warming Man said:
dv said:
After Bligh reached England in April 1790, the Admiralty despatched HMS Pandora to apprehend the mutineers. Fourteen were captured in Tahiti and imprisoned on board Pandora, which then searched without success for Christian’s party that had hidden on Pitcairn Island. After turning back towards England, Pandora ran aground on the Great Barrier Reef, with the loss of 31 crew and four prisoners from Bounty. The ten surviving detainees reached England in June 1792 and were court-martialled; four were acquitted, three were pardoned, and three were hanged——
Given the cost of these journeys and the risk to life, it seems ridiculous to send a ship to the other side of the world to capture mutineers.
A warning to others.
Let’s go to the tape.Potential Mutineer 1-: You know if we get a few of the lads together, knock the captain and 1st mate on the head and sail to a remote island we could lead the life of riley.
PM 2-: Not on your nelly, they’ll hunt us down and hang us.
I guess.
dv said:
Peak Warming Man said:
dv said:
After Bligh reached England in April 1790, the Admiralty despatched HMS Pandora to apprehend the mutineers. Fourteen were captured in Tahiti and imprisoned on board Pandora, which then searched without success for Christian’s party that had hidden on Pitcairn Island. After turning back towards England, Pandora ran aground on the Great Barrier Reef, with the loss of 31 crew and four prisoners from Bounty. The ten surviving detainees reached England in June 1792 and were court-martialled; four were acquitted, three were pardoned, and three were hanged——
Given the cost of these journeys and the risk to life, it seems ridiculous to send a ship to the other side of the world to capture mutineers.
A warning to others.
Let’s go to the tape.Potential Mutineer 1-: You know if we get a few of the lads together, knock the captain and 1st mate on the head and sail to a remote island we could lead the life of riley.
PM 2-: Not on your nelly, they’ll hunt us down and hang us.
I guess.
Mutiny couldn’t be overlooked in a sprawling empire that relied on a very authoritarian navy.