[pfredricks]

Interesting....I didnt know this, and hadn't heard it here, so thought I would mention it.
In the Sept 2003 National Geographic Adventure magazine on page 25, there is an article by Jim Thornton titled "Water on the Brain"

The article examines heat injuries in the Grand Canyon. It essentially says that when people hydrate adequately and sweat for long periods of time, they run out of salt in their blood. It actually concluded that low salt levels in the blood (aka hyponatremia) is the most prevalent heat injury in the GC saying, in fact, it is "10 to 20 times more common than heatstroke"
Solutions for this dilemma surpassed consuming just sport drinks, it actually encouraged cheap junk food snacks, like cheese/peanut butter cracker, as a better source of high concentrates of sodium.

Symptoms of hyponatremia included-the typical heat exhaustion signs plus perhaps flu like stomach symptoms, even later coma/seizures/confusion. Often observed is the thousand-yard stare.

I thought that was fascinating and vital to share as we have so many of us hiking the GC.

-Pete

[azhiker96]

Thanks for the post. I'll have to check out the article. I wonder what kind of research was done on the injuries. I've read "Over the Edge, Death in the Grand Canyon". I don't recall a single instance where death was due to hyponeutremia. That doesn't mean it's not a problem. I just wonder if it's being overblown a bit. I've washed out my system a couple of times when hiking but never when I alternated between water and a sports drink. I always take that if I'm doing a long hike, especially in the summer. Salty peanuts or almonds are great too!

[Sredfield]

A timely topic. I bonked, or whatever the word is, a week ago Sunday doing the Florida Trail up Wrightson. It was too warm, and I really sweat going up. I knew I was getting in trouble about the time we summited. Coming back I came to dread the up hill sections, although there aren't many. When we got back to the car I could hardly stand, really fatigued, nauseated, etc. I have to find the right mix of sports drinks, salty stuff, etc. I recall some hikes where I ate spanish peanuts, the redskin ones, and seem to have felt much better. Guess I"ll try some of those, and some gator aid or other mix.

[Dschur]

In response to azhiker96's reply: Since it does sort of mimic heat exhaustion it is often mistaken for it. On the trailheads for the Grand Canyon they have a warning now for it. I am not sure that they had really gotten to know it before the past few years. Just like the deep vein thromboses (sp) that is killing more people from long airplane rides they now have warnings on the cards for overseas travelling.

[Hank]

From what I've learned talking with the backcountry rangers at the Canyon, hyponatremia really is a problem there in the summer. Sports drinks, even full strength, only supply around 30% of the electrolytes the body needs, so eating salty foods is also a really good idea. (Eat, drink, and be merry...) Hank

[azhiker96]

Here's a link from the Grand Canyon website.
http://www.nps.gov/grca/backcountry/backcountry_faq.htm

The pertinent part follows:

***************
Q: How much water do I need?
A: In warm months and in addition to replacing electrolytes, each hiker should carry and drink a minimum of 1 gallon (4 liters) of water replacement each day. Hikers should drink enough so that urine frequency, clarity, and volume are normal. A hiker is not drinking enough water if their urine is dark, small in quantity, or non-existent in the course of a day's hiking. In addition eating adequate amounts of food will help you replace the electrolytes (salts) that you are sweating. If you replace the water, but not the salts, you can develop a serious and dangerous medical condition known as hyponatremia (water intoxication). If left untreated, hyponatremia can lead to seizures and possibly death.

In the hottest months of the year fluid/electrolyte loss can exceed two quarts per hour if you hike uphill in direct sunlight during the hottest part of the day. Because the inner canyon air is so dry and hot, sweat evaporates instantly making its loss almost imperceptible. It is this evaporation of sweat that allows our bodies to lose heat and stay cool. Do not wait until you start feeling thirsty to start replacing lost fluid. By the time you are thirsty, you are already dehydrated! Your body can absorb only about one quart of fluid per hour. Drink one-half to one full quart of water or electrolyte replacement drink each and every hour you are hiking in the heat. Carry your water bottle in your hand and drink small amounts often.

***************

I do disagree with their recommendation to drink before you feel thirsty. That's a great way to encourage hyponatremia. Perhaps thats part of the reason why they are having more problems with hyponatremia. People are increasing their water intake without increasing salt intake. Thirst is the way your body lets you know you need to drink. It's part of the body's process of homeostasis regulated by osmoreceptors in the hypohypothalamus.

[pfredricks]

I guess the rangers are carrying handheld hyponatremia meters

I dont want to get that water debate started again, cause there is already a thread for that in which, I believe SNICK makes some pretty good comments...........
but, i think it depends on what you define thirst as...
I agree with you if you consider thirst to be......"hmmm, I could use a nice sip of water-if it is next to me, so I dont have to get off the couch."
As opposed to.........
parched, dry mouth, gimme a drink now.
then it's too late.
I think what you are willing to pay for water is a good gauge of thirst.
If you are willing to pay $7 for a small bottle , then you are probably thirsty.
Just a thought.

[HikerInGilbert]

Well, that can be thoroughly debated. Thirst is thirst. I liked the GC quote that azhiker96 posted.

The explanation of hyponatremia is being misinterpreted quite often. The whole crux of the hyponatremia thing is that it's caused by 'drowning' your body with water. Kind of a hot weather, over hydrating because you're really thirsty kind of thing (sort of). Your body needs the electrolytes to process your water intake properly. No electrolytes, and too much water, can mean a very uncomfortable time on the trails. Not many people can get the proper balance right. Especially the casual 'I think I'll do the BA this weekend' hiker. Most wait until it's too late. Most equate it to dehydration or altitude.

I think that GC explanation says a mouthfull.

[HikerInGilbert]

As a side note...

I'm sure everyone can relate to witnessing the crusty white deposits in your hair, hat, bandanna, what ever, after a good long hike. That's a whole lot of salt your body just expelled!!

Cramped stomach muscles, calves, (etc) are a sure sign of impending doom. Headaches are also pretty common.

[sherileeaz]

As a side note...

I'm sure everyone can relate to witnessing the crusty white deposits in your hair, hat, bandanna, what ever, after a good long hike. That's a whole lot of salt your body just expelled!!

Cramped stomach muscles, calves, (etc) are a sure sign of impending doom. Headaches are also pretty common.

I definitely have had all those signs but so far been ok with my water and salt intake.

I give credit to informative sites like this. I am fortunate to have found this site before I started doing any serious hiking. I wish all hikers had the knowledge shared here. And I'm happy to read that they are now posting info of this kind at the trails.

So many times we see hikers with 1 bottle of water, nothing more. Or we've talked to hikers who have no idea what the trail is like. They have turned around because they didn't know how far the trail went, etc. We try to always pass the word on about HAZ and other sites. I don't feel anyone can ever have enough knowledge, but too little can be serious.

I feel very fortunate to have such good hiking members to discuss all this with and to learn from. Thanks!!

Sherileeaz

[pfredricks]

Science is always certainly evolving, and commonly even "experts" disagree. The Grand Canyon folks have plenty of experience and I like what they have to say. I am just throwing this out for an opportunity to share knowledge and experience. I can assure you that I have learned volumes from the great people here.
while I am glad that we can agree to disagree, but, I still believe that there are variable levels of thirst. At least for me anyway.
If one is midly thirsty, I believe that it is not to late to adequately rehydrate oneself to an adequate level. (note:"I believe") This has been my experience at least. I guess that I feel that I have learned alot about listening to my body. I will affirm that I can discern between intense and mild thirst. Same as I pay attention to my pee, mental state, fatigue, aches or anything else. It matters to me.
I will tell you that hyponatremia is not necessarily caused by drinking too much water at all. In this case it is probably a combination of sweating alot(losing salt) and furthur diluting the blood stream with excessive intake of water. It could be either or some of both. -You need to take in plenty of fluids and salt. I think that's the point.
Want to know more?
hyponatremia defined medically is ....hypo=below or less, nat=salt
emia=blood. Strictly so, it simply means not enough salt in the blood.
One can experience hyponatremia for a variety of reasons, one of which can be consuming excessive amts of water. This is called water intoxication. Water intoxication can be psychogenic in nature or caused by forced consumption of too much fluids, etc. Hyponatremia can also occur in diabetics, in SIADH (syndrome of inappropriate anti-diuretic hormone), water intoxication, or about a hundred other reasons without any sweat whatsoever.
However, the cause we are talking about here is excreting salts via the skin. Why is there salt on the skin? The body excretes salt and the water follows. Thus, leaving less in the blood stream. Salt, along with potassium and calcium are among the most important minerals in your body(aka elctrolytes). They are responsible for everything from muscle contraction to your ability to urinate. Vary the levels much and there are lots of potential complications. This can occur because the ratio of fluid to the particular mineral is changed. Lose water, the blood becomes concentrated with minerals. Too much water, the blood becomes dilute. Varying mineral concentrations can cause the same.
I just thought it an important point to make that decreasing water intake is not necessarily the important point. Ensure adequate intake of each. If your body has sufficient levels of each, it can pretty well regulate itself.
thanks,
respectfully
Pete

[flechenbones]

Interesting discussion and a topic I have been reading on lately.
Personally I stay very well hydrated even as I work. I drink at least a gallon a day and favor the use of a large water bladder system on the trail because I tend to use it more than if I have to dig in my pack for water.

Why do I stay well hydrated? Simple. Dehydration levels of 1% (water relative to body weight) increases body temperature, heart rate, and decreases performance. 2 to 3% dehydration can result in as much as 20% decrease in muscle performance. By the time that you get to 4% dehydration you are a candidate for heat stroke (or exhaustion) and muscle function may be decreased up to 30%. I have read some of this info in a number of places but most recently in Climbing: Training for Peak Performance by Clyde Soles. He concludes "water is our second most essential nutrient, after oxygen; even a small deficit has a significant effect on performance." "If you don't start hydrating until you are thirsty, it's too late - you are already down 1% and it will be hard to catch up", especially if you are still exercising. Drink early, drink often.

Hyponatremia, imho, should not be considered as the result of overdrinking, but rather an imbalance resulting from poor monitoring of your drinking & snacking. I drink quite frequently on long hikes like exiting the Grand Canyon but also take small snacks every 45 minutes or so. This helps provide energy for sustained levels of activity after the muscle's glycogen stores have been used and replaces the electrolytes that are lost through sweat. My snacks typically include gorp with peanuts (good for salt -an electrolyte), banana chips (good sources of potassium- an electrolyte which helps ward off cramps), and fig newtons (the poor man's energy bar).

For what it is worth, the same source I cited above mentions that it is often counterproductive to wash down carbo rich food (energy bars, gels, etc.) with sports drinks because the high concentration of carbos actually draws water away from the muscles and into the small intestine. I use them both but not at the same time. I often leave the sports drink for afterwards as they are easy to absorb and recovery is improved if some carbos are ingested within 30 minutes after exercise has ceased.

Just thought I would pass this info on to others.

[azhiker96]

Don't you love a good discussion? I do!
More and more I see the statement, "By the time you feel thirsty, you are already dehydrated." That sounds pretty ominous. While it's technically true, the message it gives is usually blown way out of proportion.

From Principles of Anatomy and Physiology, 10th edition, Tortora and Grabowski; "When water loss is greater than water gain, dehydration - a decrease in volume and an increase in osmolarity of body fluids - stimulates thirst." Pfredricks and others are correct in saying you may feel different levels of thirst. That's because greater dehydration results in a stronger thirst level. It's like the body saying, "Hey, I said I'm thirsty!" By drinking before you feel thirsty, you are by definition over hydrating yourself. The body can handle that as long as you make sure you replenish your salts. Also, the plants will appreciate the extra nitrogen.

Otherwise it's common sense. If you're on the trail and you feel thirsty, drink. If you get hot, stop and rest in the shade. Eat salty foods or drink something that will replenish your electolytes.

This isn't rocket science and the human body has a great ability to maintain itself and let you know if you need something. Humans have skipped about on two feet for a long time before gookinade was invented. One thing they did have that we have lost is activity. A fit body does much better in the heat than an unfit one. So get out, take a hike, know your limits, and have fun.

[flechenbones]

I agree- it isn't exactly rocket science and I wasn't trying to make anything sound ominous :)

I agree with the quote you supplied - the loss of water stimulates thirst. However, that isn't exactly saying that thirst is an immediate response to dehydration. From what I've read, thirst kicks in at about 1% dehydration. That is why drinking before you are thirsty during exercise is not actually overhydrating. In fact people rarely drink enough water during exercise to actually replace what they are losing.

Since people can lose about 1-2 liters of water per hour on a tough desert hike, I would suggest that most people are typically dehydrated, albeit mildly, and can benefit from drinking more frequently.

[pfredricks]

Here's a thread devoted to hydration-


http://hikearizona.com/dex2/viewtopic.php?t=1039

[flechenbones]

In response to pfredricks' reply:

Thanks. Wasn't around when that was discussed.

[matt gilbert]

So what about supplemental salt tablets? Are they better than electrolyte replacement drinks (ie gatorade)?

[HikerInGilbert]

In response to matt gilbert's reply:

I read in an article that the tablets are mainly made up of potassium and other electrolytes, but not sodium.

In the same article, they mentioned that Pedialyte drinks are about the closest to what the body needs to maintain proper levels all around. I'm going to check it out this weekend and see how it does. It's probably a bit on the expensive side I'm sure, but available at most stores.

Happy belated B-Day by the by...

[Snick33]

Oh Pfredricks, could you find those words I wrote about the water issue, I remember the gest of it but can't remember the context. . . . . . or should I quit while I'm ahead, (God I miss my mind sometimes)
I dont want to get that water debate started again, cause there is already a thread for that in which, I believe SNICK makes some pretty good comments...........

[Abe]

Well, I learned something today form this string. Thanks pfredricks for sharing it.

I was not even aware of, "hyponatremia", can't even pronounce it! I knew of the importance of salt and in the past I have been told that if you maintain your regular salt intake through eating, as well as, hydrating, everything would be o.k.

Frankly, anymore now, I worry about taking in to much salt.