Travel

I am sure that Fiona has got it right. When you sweat at lot, you lose salt as well as water. It is this that needs to be replaced. John Burley's link above shows that only a little salt is needed (a level 5ml teaspoon of salt to a litre of water) but IF it is needed you really need it.

The "pint of beer and a packet of crisps" for lunch is not a bad option!

I do agree with Fiona, but the general population don't just have a little too much sodium they may eat many times more than is good for them.

 It may be true that it does not apply as much to people who exercise regularly, but only if they watch what they eat, not just because they exercise. Adding sodium to the water you drink when you exercise as a principal, rather than when you need it, is unhealthy. I have moderate high blood pressure. I therefore at home keep on a diet of 3 grams of salt per day. I have to make my own salt free bread to acheive this. 3 Grams is half what doctors recommend for people with normal blood pressure and many times less than in most peoples diet.

We are all different and I totally accept that many people have come across occasions when they needed extra salt. Even thought there is so little salt in my usual diet I never have. I have drunk 6 or more litres of plain water in a day on holiday. It is true that when on holiday my diet is probably saltier than at home because I cannot control it so closely, but I never add salt myself. My holidays are mostly walking or cycling expeditions, sometimes in hot countries, cycling touring in Southern Turkey in August springs to mind.

Excluding delhi belly, cholera and things where you clearly need dioralyte, There is clearly a problem knowing when you are short of salt because you are healthy and sweating a lot, I dont think that salting all your water is a good solution. Perhaps we should suggest a few grams of salt in every litre after the first 3 litres of each day. As doctors suggest 6 grams per day in your whole diet, is something to aim for I would not suggest that 5 ml per litre counts as a few. I dont know but 5ml is maybe the same as 10 grams. With your dietary salt and say 3 litres of that you could be 7 times recommended sodium. A little bit of salt is a small pinch per litre not any sort of spoonful.

Maybe some numbers might be useful - I'm a scientist, after all

As part of a research project I monitored salt intake and loss over a 6 month period when I was training for cycle racing in Australia. My normal diet is habitually low in salt, usually around 2 to 4 g per day - partly because I was vegetarian at the time and also don't eat cheese. Even now, when I no longer train, a single helping of salami or other salty food causes a significant weight increase due to water uptake to balance the additional salt load. Luckily I have very low blood pressure as does the rest of the family. But the main point is a single long training session could result in the loss of 5 g of sodium (about 20g of salt). On several occasions, a training session had to be curtailed due to drinking only water for the purposes of the study. Sodium loss of the order of up to 1g per hour (that's nearly 4 g of salt) is pretty normal for someone (male) sweating hard in a hot environment to which they aren't yet accustomed - the scenario for a holiday abroad or a sudden hot day in the hills here. About half this is more normal for someone well acclimatised but sweating at about one litre per hour. Women generally sweat lower volumes due to lower body mass and higher surface area/mass.

Drinking enough pure water when you're working hard is also difficult as it tends to sit in the stomach and slosh around which reduces your desire to drink more - thus you can end up dehydrated despite drinking. This might not matter much if it's a single hard game of squash but if you're doing the exercise day after day - training or trekking in mountainous terrain in a hot climate, say - it's a bit stupid to expect your body to go on performing as you want if you ignore some basic common sense. Loss of too much salt due to drinking excess amounts of plain water can result in nausea, dizziness, loss of energy and appetite and eventually death (in extreme circumstances).

5 ml of salt sounds like a teaspoon full - or about 5g - this does sound too much, in fact I'd suggest that it would be quite difficult to drink something so salty unless it was also very hightly flavoured.  I would have thought 1- 2 g salt per litre would be sufficient and make the rest up with a packet of crisps, a cheese sarnie or some of the local charcuterie, depending on what's available.

Getting down to numbers sound good Fiona. Can you confirm the ratio of Sodium to salt which I thought was about 1 to 2.5 specifically 23mol wt sodium to 58 mol wt Sodium Chloride wheras you are saying nearly 1 to 4. Surely salt weighs more than 1 gram per ml otherwise it would always float. As I said I guess it might have a density of 2 grams per ml. edit And looking up on Wikipedia its density is 2.165.

The result of this is that salt is very easy to have too much of. Even easier than you said.

Do you agree that people may be getting 6 grams a day or more from their diet. And that my suggestion of adding salt to any water drunk after the first 3 litres in any day and then adding it at about 3 grams per litre which is 1.5 millilitre per litre (1.5 cubic centimeter), maybe 3 large pinches, would give sodium balance.

You can get the stomach to absorb water more quickly by adding sugar a small amount of salt is not going to make a lot of difference.

Your research did it come up with any information on the amount of salt in sweat? I understood that people with low salt diets sweated less salty sweat.

Whoops - mistake in the maths somewhere - always a problem swopping between sodium and NaCl.

I just checked the post again and you're correct Derek, NaCl is Mwt of 59 (23 + 36) so 1 g of sodium is equivalent to 2 and a half g of NaCl - no idea where I got the factor of 4 from - doing two jobs at once is probably the answer.

I'd definitely agree that most people eat 6g or more of salt daily from a typical modern diet. I'm always horrified at how much salt is hdden in innocuous foods like breakfast cereals. Even my soya milk has salt - although I made my own without and it's horrible

I would agree that you only need to add salt to drinks if you're significantly exceeding your normal fluid intake. I wouldn't like to say whether that is 3 litres or more or less as this is pretty individual. I know people who by my standards (I'm a heavy drinker - I love sparkling water and have a Soda Stream to add CO2 - but no Na - to my normal drinking water) don't drink at all - maybe three cups of tea or coffee and a soft drink each day. As they don't dry up, they're clearly not getting more and more dehydrated but with this low level of fluid intake, they're not flushing much salt out of their bodies. So suddenly taking on an additional 3 litres of fluid a day could be dreadful - or reduce their blood pressure dramatically. I think you have to learn what's appropriate for you. I think that I'm probably at the salt sensitive end of the scale, possibly because I eat so little salt and seem to run happily on fairly low levels. But it's a bit of a chicken and egg situation - does my body dictate my preferences for what I eat or does the low blodd pressure come from the fact I eat little salt ( I think it's more complex than this but you get my drift).

On the numbers - sweat is typically around 20 millimolar Na (~0.5g/L) for a fit, heat acclimatised individual. But it's very variable both for individuals (environmental conditions, fitness, general health) and between individuals - so high salt sweaters might have concentrations 3-4 times this.

Note that on the 5 ml = 5g - a teaspoon of salt is a heap of grains (not a solid lump) and has a porosity of about 45%, depending on packing and grain size distribution, thus the density of the solid is about twice the mass/volume of the bulk grains. Look what happens when you ask a scientist questions - all sort of esoteric information comes out

Personally I find I can drink loads on a hot UK day just to stay hydrated or to minimise de-hydration. I drink only water so I guess I must be sweating ouut what I am putting in. Since I almost always consume 3 litres on a typicaly day in summer and go home de-hydrated (worst day I had was 9 litres and a de-hydration headache and that was doing Ben Lomond not a hard walk). I am guessing with that level of sweating I am losing salts at high rate. I also have very low blood pressure which contrary to the old thinking is considered to be detrimental to ones health. In our family other low blood pressure people have been told to increase their salt intake by doctors.

Whilst I am no expert and some of you seem to be, it does seem to me that I am one of those people who would benefit from electrolytes while walking. For backpacking trips I once got some Nuun tablets with a view to using after aquamira water treatment to reduce the taste taint. I have also started to use in the last, estimated 500ml in my 3 litre source baldder for the end of the walk and while travelling home. Since I have done this I have always felt slightly better on arriving home and have stopped the mad drinking I do once I get home. Basically I often feel incredibly thirsty once I get home  and drink loads of fruit juice and V8 vegetaable juice.

I think walking can quite easily bring you outside of the normal diet situation so salt replacement solutions like electrolyte tablets are something it is wise to carry. As far as the OP's overland trip is concerned surely some elctrolyte powder or tablets such as dioralyte something worth carrying even if it is for more extreme use like after Delhi Belly.

One old folk remedy I have for recovery after / during sickness and/or the squits is the one told to me by my old, old, old GP (or at least it sounded like this what with the slurring and Scottish accent). He said coca cola left to go completely flat. He did say it had to be that brand too. Which considering the effect it has on the bugs at Holme Pierrepont National whitewater centre makes sense. For the  non-paddlers out there this centre had a reputation for making people ill with stomach complaints. It was found out (or at least anecdotally) that coca cola when drunk straight after paddling there prevented the stomach problems developing within a few hours of paddling there. Since I believe one of the few kayakers to contract Hepatitus while paddling got it there you can quite understand how people would clutch at anything.

I am not recommending coca cola over the electrolytes BTW just suggesting that you can get what you need for a lot of the time from normal stuff but can't hurt to have the special stuff for when it really is needed.

Ramble over.

Why is sodium bad and potassium is not considered as bad as sodium?

Thanks Fiona,

I can see my mistake so 5ml salt is equivalent to 6 grams by your figures.

To take some one like me, fit and used a low salt diet, drinking 6 litres in a day I might loose as little as 20 x 23 milligrams sodium x 2.5= 1 gram salt per litre. Therefore sweating 6 grams in a day of which 3 grams I get from my diet so I could add a gram of salt to the last 3 litres and be in balance. A gram of salt is about 2 large pinches.

At the other extreme a high salt sweater getting 10 grams per day from their diet sweating 6 litres might loose 24 grams in sweat and need to have 4 grams added to each of the last 4 litres. They would need 3ml of salt per litre but with the first 2 litres every day salt free. So that is an upper limit of half a 5 ml teaspoon per litre. after the first 2 litres. That would be incredibly salty

I am surprised that the body of some one on a high salt diet does not respond to lowered sodium levels by reducing the salt in their sweat. If that did happen on the first day the 5 gram figure would be too high.

I was not estimating what peoples normal drinking volume was, I was just using up peoples estimated dietry salt intake on the first few litres until it was sweated out/used up.

Time To Go,

Potassium in excess is poisonous and bad for you. But it is not normally added to food. The potassium in food is naturally there. Sodium on the other hand is considered to improve taste so it is added in handfuls. Your body works best with the correct proportion of Sodium to Potassium which is round about what is naturally found in food.

What we are trying to come to is a guide as to how much common salt to add to your drink if you have sweated more than normal. It is clear that a little salt added to at least some of your replacement water is good. It is clear to me that people over do that. Whether people should also add potassium salt, and Calcium and Magnesium................ is another question

mmmm

or just make a 50/50 mix of orange juice and water and add a pinch of salt per litre.

Job done 

welcome to OM Jason - as long as you arent a spammer pushing iffy rehydration stuff

Ooh, what makes you think that, GOF? First time poster dredging up a 2.5 year old thread with a shop linky. Shurely not a spammer?!