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Is it more efficient for me to carry water in a bottle or in my stomach?
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Sam Edge
Ringwood, Hampshire, UK
If it is a 1000-litre bottle, then I would carry it, preferably with mechanical assistance, as attempting to drink that much would kill you. However, for taking sufficient water to stay hydrated when walking or running or otherwise exerting oneself away from a source of clean water, there are a couple of things to consider.
In Frank Herbert鈥檚 Dune novels, the Fremen people of the desert world Arrakis use 鈥渟tillsuits鈥� that capture all water from sweat, urine and faeces. They also have mouth and nose pieces that capture and recycle body moisture before storing that water in pockets distributed around the suit. Even with the stillsuits, the Fremen are advised to stay as hydrated as possible.
Outside of Dune, though, if your body has too much water, it reduces the concentration of important ions such as sodium and those of other minerals and interferes with the osmotic processes of your cells. To counter this, you may sweat more, and your body will dump the excess into your bladder and from there out of the body.
If you're going to be away from sources of potable water, carry some in bottles, ideally distributed evenly around your torso
So, drink as much as you like without making yourself uncomfortable before you set off on a journey, as having it distributed throughout your body is the most efficient way of carrying fluid. However, if you鈥檙e going to be away from sources of potable water for a while, carry a backup, ideally in multiple smaller, lightweight containers distributed evenly around your torso.
Of course, if you are shy about peeing outdoors or are going to be in an urban area where doing so may be construed as unsanitary, you might not want to overdo it with the pre-hydrating!
Mike Follows
Sutton Coldfield, West Midlands, UK
It is better to carry it in a bottle, as it allows you to drink when thirsty. When you drink water, it passes through your digestive system and is absorbed into your bloodstream through the intestines. However, the stomach isn鈥檛 designed to store water.
Maintaining proper water levels is essential for supporting cellular function and vital processes. This is part of our homeostatic system, which includes osmoregulation 鈥� the process by which the body balances water and salts.
This works via osmoreceptors in the hypothalamus in the brain detecting changes in blood osmolarity (which describes the concentration of solutes, such as sodium). If osmolarity increases, that means the concentration of minerals has gone up, indicating dehydration. The brain then triggers the thirst reflex to encourage fluid intake and tries to conserve water by reducing urine output.
It cuts the amount of urine produced thanks to the hypothalamus signalling the release of antidiuretic hormone (ADH). ADH acts on the kidneys, making them more permeable to water. This allows these organs to reabsorb more water back into the bloodstream rather than excreting it in urine. However, if you drink water before going on a walk, your kidneys direct a significant proportion to the bladder, from where it can鈥檛 be reabsorbed.
The situation becomes more challenging in hot conditions when sweat glands release more water onto the skin鈥檚 surface. This water evaporates, removing energy from the body in the process, helping prevent overheating. Without a source of water to quench your thirst and restore salt balance, you risk suffering from heat exhaustion or even heat stroke, which can be fatal. Water is also lost through exhalation as vapour in your breath, particularly when breathing heavily or in cold, dry conditions.
It is a good idea to drink plenty of water before you start your walk to avoid drinking supplies you are carrying too soon, which could leave you with insufficient for the rest of the hike. To stay properly hydrated, carry sufficient water in a bladder or bottle before setting off on a long walk, particularly when expecting more severe physical exertion, such as when climbing a mountain or on a hot day.
It is also wise to bring purification tablets, allowing you to access water more safely from streams if you run out. However, this should be considered a last resort and ideally you should use sources as high up as possible, where the water has less chance of being contaminated 鈥� by something like a dead sheep, for example.
Tony Green
Ipswich, Suffolk, UK
Let鈥檚 consider my options when I go for a long cycle ride on a hot summer鈥檚 day. I can take 1 or 2 litres of water in bottles, or I could drink all that water before I set off.
With the bottles, I can take a drink whenever I feel thirsty, and the water will last me until I am home. If I drink it all before setting off, it is likely to go through me quite quickly, and much of it will be excreted fairly early in my ride.
The first option ensures that I arrive home without getting dehydrated, whereas the second probably guarantees dehydration. And given that I can鈥檛 cycle as efficiently dehydrated, carrying water in bottles is my most efficient choice.
Hillary Shaw
Shropshire, UK
As someone who regularly does 5-hour walks, I recommend using a bottle to carry water 鈥� but drink it regularly and gradually.
Carrying a bottle in a rucksack, for example, does feel heavier than carrying the same volume of water in your stomach. However, the body will try to maintain internal homeostasis, and you will soon lose that water by urinating more. If you carry water in a bottle, at least as you get more tired, the load in your rucksack gets lighter.
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