How Long to Digest Water: Helpful Facts About Water Absorption

Some basic knowledge of your body’s functions, combined with knowing how long to digest water, and how to treat water from streams and rivers will ensure that you consume the right amount of water whilst also knowing how to make sure it’s safe to drink.

Whilst you probably know to throw a bottle of water or two in your backpack when you’re heading off for a hike, you might not have thought too much about all the processes your body goes through in order to keep you hydrated and feeling great.

On a small scale, water is absorbed into your body as soon as you take that first sip, but most absorption takes place in your large intestine, which is one of the last sections of your digestive system before waste is expelled.

You might be wondering how long does water stay in your stomach, but the answer depends on whether or not your stomach is empty or not.

So why does it matter if my stomach is full?

If you haven’t had anything to eat and you take a drink of water, within five minutes the water passes through your stomach and into the large intestine. From there it passes into the bloodstream. This will mean that you are rehydrated quickly and effectively.

If you have been hiking quickly and have an elevated heart rate and core body temperature, it’s also important to note that this process of water absorption into the bloodstream is quickest if you drink cold water.

The reason for this is thought to be that the cool water helps reduce your internal temperature and helps it settle back down into its normal range of around 98.6 F.

If you’re stopping for lunch and are eating at the same time as you’re drinking, it can take more than 45 minutes before the water passes through the stomach and into your intestines. This is because your stomach is working to digest your food first.

On average then, it takes anywhere between five minutes and two hours for the water to be completely absorbed into the bloodstream.

So, if you’re feeling dehydrated because it’s a really hot day and you forgot to drink more than usual to compensate for the extra fluid lost from sweating, in order to quickly rehydrate yourself, make sure you drink before you eat.

It’s generally recommended to drink little and often whilst you’re hiking, in order to maintain hydration levels. Whilst you might enjoy having a drink with your lunch, this won’t necessarily affect your hydration levels as quickly, so this drink could be a lemonade or fruit juice which can make a nice change from water.

How to stay hydrated when you’re hiking

Whilst you need to drink around a liter of water a day normally, this will increase when hiking or doing any activity that raises your heart rate. There’s a few great tips to make sure you stay well hydrated throughout your hike, including:

  • Before you set off, drink one or two cups of water, juice or an electrolyte-based sports drink.
  • Limit caffeinated drinks like tea, coffee and cola. This is because they can cause you to become dehydrated.
  • Use a Camelback or bladder-based hydration system so you can drink on the move. Carry bottles of water with you as well so you can have a longer drink at rest stops.
  • Drink at least a quart of fluid per hour when it’s hot or you are sweating from strenuous activity
  • Consider taking an electrolyte-based sports drink to retain fluids and boost energy, but don’t replace plain water altogether
  • Once you finish hiking, continue drinking to help replace lost fluids.
  • Rehydration will be more effective if you also consume potassium or sodium rich foods such as bananas or citrus fruits.

Make sure you are aware of the signs of dehydration and can recognize these both in yourself and others. The signs include:

  • Weakness
  • Excessive fatigue
  • Rapid heart rate
  • Low volumes of dark urine, or painful urination
  • Dizziness

Continuing to hike in a dehydrated state can have serious consequences for your health, including heat stroke, muscle breakdown and kidney failure. So if you spot any of the signs listed above in yourself or your friends, make sure you take a break and have a long drink of water. When you set off again, remember to drink little and often as you’re hiking.

The importance of staying hydrated

Drinking enough water is essential to staying healthy and allowing your body to maintain the effective functioning of every single system in your body, including your heart, brain and muscles. Fluids also carry nutrients to your cells, flush away bacteria and prevent constipation.

Your body can’t really store water as such, it will absorb what is needed as you drink, and then expel the rest as urine. So drinking little and often means your body is able to constantly absorb what it needs when it needs it.

How much should I be drinking?

A healthy adult should aim to drink around one or one and a half liters of water a day. This should be throughout the day to ensure your hydration levels stay high rather than rising when you drink a large quantity of water in a short time and falling again as you stop drinking.

Expect to drink more than this when hiking as you will be using more energy as well as sweating more. If you know that in theory you have been drinking enough not to be dehydrated, but you still feel thirsty, then there are a few things to do in order to maximize your bodies’ absorption of water:

Make sure that you are getting enough salt

Although many people automatically assume that salt in your diet is bad, you do need to ensure that you are getting enough, especially if you exercise a lot, as salt will be lost through your sweat. Salt is important because the bodies’ cells use it to help retain water.

So if you haven’t got enough salt in your diet your body will be struggling to stay hydrated even if you are drinking lots of water. Your body also uses salt to maximize the absorption of nutrients in the small intestine.

Eating foods that are high in fiber

This food also helps ensure that water is retained in your large intestines, from where it can be absorbed into the bloodstream slowly. Without fibrous foods, the water will pass through the intestines much more quickly, which means that more of it will be passed out as urine and less absorbed into the bloodstream.

An easy way to tell if you’re drinking enough water, is that your urine should be the color of pale straw. If it’s any darker, that can be a tell-tale sign that you’re not as well hydrated as you should be.

The importance of clean drinking water

When you’re out on a long hike you probably won’t be able to carry all the water you need, but it’s important to ensure that any water you supplement your supply with is safe to drink.

See also: Does Boiling Water Purify It: Myths and Safe Practices

If you’re considering drinking from a stream or river crossing, it’s essential you stop and take the time to treat it first. Whilst that beautiful stream might look crystal clear, you can guarantee that it will be teeming with bacteria and other organisms which could make you seriously ill.

You never know, there may well be a dead animal carcass just upriver, animal feces on the bank or debris from someone not following recommended procedures and washing their dishes in the stream.

When out hiking then, it’s safest to assume that all water sources are contaminated, and then treat them accordingly. Read on for some information into the most common water borne diseases and how to remove them.

Water borne diseases and how to safely remove them

Water borne diseases are simply caused by drinking contaminated or dirty water. The contaminants could be anything from bacteria, viruses or parasites.

The handy table below explains some of the most common water borne diseases in a bit more detail.

NameTypePotential health effectsSourcesRecommended methods to remove safelyMethods NOT recommended
CryptosporidiumProtozoaGastrointestinal illness (diarrhea, vomiting, cramps)Human and animal fecal waste✓Boiling
✓Filtration (using filter size 1 micron or less)

✓Combined filtration and disinfection with chlorine dioxide
✗ Disinfection with chlorine or iodine
✗ Disinfection with chlorine dioxide
Giardia intestinalis (Giardia lamblia)ProtozoaGastrointestinal illness (diarrhea, vomiting, cramps)Human and animal fecal waste✓Boiling
✓Filtration (using filter size 1 micron or less)

✓Disinfection with chlorine dioxide

✓Combined filtration and disinfection with chlorine dioxide
✗ Disinfection with chlorine or iodine
Campylobacter, Salmonella, Shigella, E.coliBacteriaGastrointestinal illness (diarrhea, vomiting, cramps)Human and animal fecal waste✓Boiling
✓Disinfection with iodine or chlorine

✓Disinfection with chlorine dioxide

✓Combination filtration and disinfection (filter size of 0.3 micron or less)

✓Filtration (moderate effectiveness only)
Enterovirus, hepatitis A, norovirus, rotavirusVirusesGastrointestinal illness (diarrhea, vomiting, cramps), hepatitis, meningitisHuman and animal fecal waste✓Boiling
✓Disinfection with iodine or chlorine

✓Disinfection with chlorine dioxide
✗ Filtration

As you can see, when treating potentially contaminated sources of water, boiling is the most effective method which should kill all pathogens. In all cases, water should be brought to a rolling boil for one minute. At altitudes of more than 2000 meters, you should boil the water for three minutes.

If you don’t want to carry a stove then the next best option is a two-step process involving filtration then disinfection. Ensure that your filter has a small enough pore size (1 micron or less for protozoa, 0.3 micron or less for bacteria), but bear in mind that filtration is not effective against viruses.

After filtration you also need to treat the water with a disinfectant such as chlorine or iodine. Besr in mind that the efficacy of any disinfectant will be affected by contact time, concentration of disinfectant, water temperature, water turbidity (cloudiness) and water pH.

It’s very important that you make sure that you follow the manufacturer’s guidelines for your chosen filter and disinfectant. For tips on how to make your DIY water filter, follow the instructions written on our earlier article on this topic.

It is worth noting that water that has been disinfected with iodine is NOT suitable for pregnant women, people with thyroid problems or hypersensitivity to iodine. It is also not suitable for continuous use for more than a few weeks at a time, so if you’re on a long trail you will probably want to consider taking a different choice of disinfectant with you.

I drink enough water but I’m still thirsty…

If, after ensuring that you drink enough water, are eating enough salt and fiber but are still thirsty all the time, it might be a good idea to visit your healthcare professional as there are some medical conditions including Adrenal Fatigue and certain types of diabetes which will mean you will always feel thirst no matter how much you drink.

So what’s the best way to ensure I’m drinking enough water?

Drink little and often, preferably before you start to feel thirsty. If you struggle to drink enough water on its own, try adding infusions to the water to make it more palatable.

This can be some slices of lemon, cucumber or perhaps some mint. You can now buy water bottles with special containers to hold the infusing ingredients separate from the water. You can also check our tips on how to choose the best electrolyte supplement to ensure proper hydration.

It is so important to treat ALL water obtained from rivers or streams. Decide on your chosen method of treatment, and if you’re using a filter and then disinfectant, make sure you’re fully aware of the instructions for your specific equipment.

If you hike regularly with a buddy, you might want to consider taking more than one method to ensure you can always treat your water.

Accidents can happen and you might forget to check you have enough fuel in your stove, disinfectant drops can leak and filters can end up torn. You don’t want to be left in a situation where you don’t have the means to treat contaminated water but are very thirsty.

Consider the timing of when you drink. The majority of water will be absorbed within two hours, make sure you have a drink before you set off on your hike. Drinking on an empty stomach will also help to make sure that the maximum amount of water is absorbed into the bloodstream quickly and easily.

If you follow all these steps, you’re giving your body the best possible chance to stay well hydrated safely, and allowing you to enjoy a day out on your favorite trail.

If you think we’ve missed your preferred method of safely treating water or you have some great tips on staying hydrated, be sure to leave us a comment.


6 thoughts on “How Long to Digest Water: Helpful Facts About Water Absorption”

  1. Thank you so much Jerry for listing the signs of dehydration. I had a friend who was already on the brink of fainting during one of her hikes because of this. All of her companions did not notice the warning signs. It is really important to know what to do in cases like this.

  2. Your list on how to stay hydrated is awesome. I will surely take note of it all. I have never heard about limiting caffeinated drinks though. I really love coffee and I even bring a couple of sachets when I hike, but now, maybe I will try to cut it of.

  3. Most people get dehydrated or overhydrated simply because they don’t know the importance of water to the human body, and the effects of drinking too much water. The info should enlighten you.

  4. Hiking in a dehydrated state is definitely a bad idea, which can result to kidney failure, muscle breakdown, and heat stroke. Such are the kinds of things you can learn from this article. Remember to bookmark this page for reference.


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