How Much Water Should You Drink?

How much water should you drink? This is actually a very important part of setting up your diet correctly, and if you search this up online, you will be exposed to quite a lot of poor information and even misinformation. 

So, the goal of this article is to clear up any confusion about how much water you should drink, and to help you better understand the role of water and its impact on your health. 

But I don’t want to just give you an un-contextualised answer. I want to give you the information you need to actually be able to tailor your water intake specifically to your needs (or the needs of your clients, as I know a lot of personal trainers, coaches and nutritionists read our content).

This article is still a part of the larger article series on how to set up the diet. So far in that article series, we have discussed setting up the calories for the diet, how much protein should you eat, how much fat should you eat, how much carbohydrate you should eat, how much fibre you should eat and now we turn our attention to water intake.

Although technically not classified as a macronutrient, water is essential to life and needs to be consumed in macronutrient-sized quantities. So we are going to class it as a macronutrient for this discussion.

Before we get stuck in, I would just like to remind you that we offer comprehensive online coaching. So if you need help with your own exercise program or nutrition, don’t hesitate to reach out. If you are a coach (or aspiring coach) and want to learn how to coach nutrition, then consider signing up to our Nutrition Coach Certification course. We do also have an exercise program design course in the works, if you are a coach who wants to learn more about effective program design and how to coach it. We do have other courses available too.

The Role Of Water

To understand the role of water, we must peer back into our evolutionary past. You see, life evolved initially in an aquatic environment. And I don’t just mean that we evolved from animals/creatures that swam in the sea (that is also true). No, I mean cells themselves evolved in the water. 

The current thinking (we are not certain of exactly how it happened) on how life came to be, involves water. It is supposed that some amino acids got enclosed in a lipid bilayer, and through some randomness became some sort of self-replicating protein (RNA is often thought to be the molecule that effectively started life). However, a lipid bilayer only forms because it has water around it (hydrophobic and hydrophilic interactions cause the lipids to form that shape). 

No water, no lipid bilayers, and likely no life. 

However, beyond that, water (or its molecules of oxygen and hydrogen) is also used in many reactions in the cells. They evolved in this water environment, and evolution is all about using whatever is available at that time. As a result, the proteins (such as enzymes, scaffold proteins, chaperone proteins etc.) in our cells likely use water in some manner to carry out their job (even if it is just using water to dilute toxic byproducts or keeping pH in an acceptable range). 

Basically, cells evolved in water and as a result, they evolved to use water for many of the processes they perform. 

The fact that we likely evolved in seawater is also important, as seawater isn’t just pure H2O. It contains salts, and as I said, evolution takes advantage of what it has available. So these salts, or electrolytes as they are referred to in the body, are also important to the discussion of water. 

As life evolved to live on land, they had to adapt to a new environment. The way they did this was to effectively bring a bit of the sea with them wherever they went, and this is effectively what cells do.

Now, beyond that little pre-historic tidbit, we want to know what the actual role of water is in the body. Understanding the role of water will allow you to see just how important it is and to understand why it is so important to prioritise your water intake. So let’s dig into it.

Water and Hydration

Beyond that somewhat esoteric discussion of our very cells being formed due to water, we do actually need water for more easily understandable reasons. The first is hydration. This is effectively saying, we need water because our cells evolved in a water environment, but that isn’t the way most people think of it. So I am going to say it how most people think of it and just say we need water to stay hydrated. 

Without water, our cells simply don’t work. This is what I meant when I said cells effectively bring saltwater with them wherever they go. All your cells contain water and salts, and this is vital to their proper functioning. So when someone talks about drinking water to “hydrate”, this is what they mean. 

This also explains why electrolytes are an important part of the discussion around water, as the cells want to maintain a certain level of these electrolytes (to somewhat mimic the seawater they evolved in). If you leave cells on a glass slide, they will dry out and then stop functioning, so hydration is vital to cell survival. Without even considering any other role of water, fundamentally, without water, cells cease being cells and they die. So water is vital to life (at least for humans).

Now, it does bear keeping in mind that it isn’t just water that is important, the dissolved minerals within the water are also important. As I said, evolution uses what it has available, and it evolved with these minerals available. 

At a very fundamental level, these minerals facilitate the flow of electrical currents and this is another vital part of life. You can think of life as being a bio-electrical event, and this is facilitated by these minerals. This is why they are called electrolytes when discussing them in relation to nutrition/physiology. 

Cells use the fact that these electrolytes have electrical charges to move stuff in and out of the cell (effectively, to do work), as regulatory molecules and as key components of many cellular activities. Drinking water with electrolytes results in better hydration (of course, only up to a point, you can have too much of these electrolytes, and this is why you can’t drink seawater), and this is because the cells are more easily able to keep the right balance of electrolytes to water (i.e. the right level of dilution). 

Without electrolytes in the water, your cells can’t take in as much water because it results in a dilution of the concentration of electrolytes. This results in the cells not being able to perform their jobs due to too low a concentration of electrolytes (they are used in certain processes in the cell and also as a “gradient” for other molecules to regulate the passage of other electrolytes through the lipid bilayer). 

So any discussion of water does naturally need to extend to a discussion of electrolytes. It should also be noted that water is not the only source of electrolytes, they are in the food we eat, and obviously, they are also the salts we use to season our food.

However, beyond just the cells being hydrated, water intake also makes your blood hydrated. Which in turn is what brings stuff (including water) to your cells. Without adequate water, your blood becomes “thicker” and thus your blood pressure goes up to try and pump this thick blood around your circulatory system. 

From having a passing knowledge of health-related things, you likely know that having high blood pressure isn’t a good sign for your health. But it may surprise you to realise that being adequately hydrated is one of the simplest ways to reduce high blood pressure. However, maybe you don’t care too much about where your blood pressure is currently, you are young and fit, so who cares, right? 

Well, another point to remember about adequately hydrated blood is that it leads to better performance both physical and mental, and at the very least, it leads to better muscular pumps from resistance training. So if you want to improve performance and thus body composition, ensuring water intake is on point is a very smart move.

Water and Nutrient Delivery and Storage

Your blood is the superhighway that gets things where they need to be in your body. Without blood, you simply wouldn’t be able to survive. Water is a vital part of blood flow, as water is over 50% of your blood volume (not accounting for the water content of red blood cells themselves). 

So water is essential to the assimilation of all the nutrients that you eat, and as a result, it should definitely be something that is prioritised along with the actual calorie-contributing components of the diet. However, beyond the actual food components of nutrient delivery, blood also brings oxygen to your cells. Without an adequate supply of oxygen, your cells simply don’t work. 

So being adequately hydrated actually makes every breath you take more effective. This is obviously super important for health, but you should be able to see this is super important for performance (both mental and physical) and thus body composition.

Water is essential for nutrient delivery, as it is intrinsically involved in the nutrient delivery system of the body (the blood and the circulatory system). However, it is also involved in the actual storage of nutrients too. It is not only the medium through which nutrients actually get delivered to the cells of our body, but it is also involved in how those nutrients actually get stored in the cells. 

This is especially true for carbohydrates, as for every gram of carbohydrates you store, ~3 grams of water are also pulled into the cell those carbohydrates are stored in. Water is thus essential to the proper storage and use of the carbohydrates you eat. 

This is why you often see people who resistance train to advocate for high carbohydrate and water intake, as you can literally feel and see this effect as your muscles become fuller and you get a pump more easily. This is obviously also helped by the blood flow stuff too. It should be noted that this isn’t just an aesthetic thing, being hydrated also improves training performance. 

Once you really understand that water is both delivering nutrients to your cells, and also involved in storing nutrients in your cell, you really start to realise that water intake is definitely something that should be prioritised. But further to the delivery and storage stuff, water is also involved in nutrient metabolism itself, as it plays a role in many enzymatic reactions and is involved in clearing the metabolic waste from these reactions.

Water and Enzyme Activity

The very enzymes in your cells that catalyse the reactions your body needs to be healthy, perform well and survive long term, generally require water in some manner (this does apply to all proteins within your cells in general, but this can seem a bit esoteric unless you have a deep understanding of biochemistry). They may require water to facilitate the substrates they act on actually getting to them, they may require water to actually stabilise their structure, they may require water to stabilise their polarity, and water may actually be involved in the actual enzymatic reaction itself (either as a product or substrate). Without water, the enzymes needed for your cells to actually do their job simply don’t work. 

While understanding some of the stuff that water is used for in relation to enzymes does require you to know and understand some basic organic chemistry and perhaps some biochemistry, you don’t actually need to understand it too deeply to know that water is a key component of these enzymes working effectively. Probably the easiest one to understand is that water interacts with acidity in the cell, which influences enzyme activity.

Water influences the pH (the measure of acidity or baseness of a substance), and enzymes require a certain pH range for them to function optimally. Too much acidity or too much “baseness” (alkalinity) and the enzymes either don’t function or they begin to unravel and thus cease to exist. Water is the key player that cells use to manage the pH of the different components of the cell and thus manage enzyme activity. 

Some enzyme reactions result in protons being released (which increases the acidity), and water is used to “dilute” these protons and keep the cell at an optimal pH. This naturally enough should get you thinking about one of the reasons people reach failure on an exercise, which is acidosis. Adequate hydration potentially allows you to deal with more protons being released in the cell as it is effectively acting to dilute the acidity of the cell. 

So better hydration means the potential for a few extra reps in the gym or a slight increase in performance for whatever activity you are doing. This small edge adds up over time to fairly significantly increase performance. 

Related to this is the fact that adequate hydration is not only improving blood flow to the muscles, but it is also improving blood flow away from the muscles. The cells may be using water to help buffer acidosis, but they are also using water to get rid of waste products (including metabolic waste products). Water is vital for the proper detoxification of your cells.

Water and Detoxification

Not only is water involved in making the enzymes in your cells work correctly, but it is also involved in facilitating the detoxification of the cells. The processes within cells generally aren’t 100% efficient and it is the case that some waste products are generated as part of doing the things a cell needs to do. 

Very basically, blood flow goes to and from the cell, and water is involved in keeping the blood flowing efficiently. So the cell releases its waste into the bloodstream, and this is then taken away from the cells to the appropriate areas of the body to get rid of them. However, those organs that are responsible for dealing with these waste products also use water to deal with these waste products. 

The kidneys and liver are the two organs generally considered to be responsible for dealing with waste products, and they both heavily use water to do so. However, other organ systems in your body are also responsible for dealing with waste products, such as the lungs, skin, the digestive tract (especially the lower portion) and the bladder/urinary tract. Your body gets rid of stuff it doesn’t want through sweat, respiration (breathing water vapour and CO2 out), digestive/excretive tract products and urinary tract products. Water is essential to all of these processes working correctly.

While we could very easily deep dive into all of these processes and get a better understanding of why water is important, it really isn’t necessary here. However, as it applies to nutrition, what does bear keeping in mind and understanding is the fact that water is essential for the proper functioning of the digestive tract. 

All digestion involves water, as the digestive process involves breaking all the food we eat into a liquid chyme and it uses acid to do so. Water is intrinsically involved in this whole process. However, it is also involved in actually moving the digested/digesting foodstuff through the entire digestive tract. 

This is one of the reasons you will quite often see increased water intake recommended for those who are dealing with digestive issues, especially constipation (as more water in the stool makes excretion easier, and the type of fibre you eat also plays into this, as you will remember from the last article in this series). So water is very important for the digestion of all the food you eat, and the proper passage of undigested foodstuffs (and waste products) through the digestive/excretive tract. To an extent, the more hydrated you are, the better your digestion works.

Water does have other roles in the body, but you hopefully get the point that it is pretty central to the proper functioning of the body. As with all these discussions, we have to actually ask whether any of this stuff has any impact on our overall health. I mean, it is pretty useless to learn that water has some pretty vital roles in your body if this ultimately has no impact on your health whether you consume enough or don’t. 

So, let’s turn our attention to water and health.

Water and Health

Proper hydration is essential for maintaining overall health and ensuring that the body functions optimally. There are numerous health benefits to drinking sufficient water, such as:

Supports Physical Performance

Staying hydrated maintains blood flow to muscles and helps regulate body temperature, reducing fatigue during exercise or physical activity. This potentially leads to enhanced endurance and strength, especially over time. 

Proper hydration also reduces the risk of muscle cramps by helping to maintain electrolyte balance.

Water helps deliver nutrients to muscles and flushes out waste products, speeding up post-exercise recovery.

Improves Brain Function and Mental Clarity

It’s not just physical performance that is boosted by sufficient hydration, so too is cognitive performance. Proper hydration ensures oxygen and nutrients are efficiently delivered to the brain, improving cognitive performance. This is generally most obviously seen in a boost in focus and concentration.

Even mild dehydration can lead to irritability, fatigue, and difficulty concentrating. Sufficient hydration enhances mood and reduces fatigue. Hydration levels are also closely linked to short-term memory and decision-making abilities. 

Promotes Digestive Health

Adequate water intake helps keep the digestive system moving, softening stools and facilitating bowel movements. Water is essential for breaking down food and transporting nutrients to cells. It helps in producing stomach acid and digestive enzymes, which are crucial for breaking down food.

Ultimately, adequate water intake is associated with improved digestion and overall digestive health. 

Maintains Kidney Health

Proper hydration dilutes urine, reducing the concentration of minerals that can form kidney stones.

Water flushes toxins and waste products out of the body through urine, and supports waste elimination.

Drinking enough water also helps prevent urinary tract infections by promoting regular urination, which clears bacteria from the urinary tract.

Enhances Skin Health

Proper hydration also keeps skin hydrated, reducing dryness and promoting a more youthful appearance. Being sufficiently hydrated improves skin elasticity and makes the skin appear more firm and supple. Hydrated skin is also less prone to wrinkles and fine lines.

Water helps eliminate toxins from the body and detoxifies the skin, which can improve skin clarity and reduce acne. 

Regulates Body Temperature

Water enables the body to produce sweat, a crucial mechanism for cooling down during heat or exercise.

Staying hydrated reduces the risk of heat-related illnesses (such as heat stroke) in hot climates or during physical exertion.

Supports Cardiovascular Health

Proper hydration ensures blood remains adequately diluted, supporting healthy blood pressure levels. This doesn’t seem like much, but it is actually incredibly important for overall health and reducing cardiovascular disease risk. 

A well-hydrated body also makes it easier for the heart to pump blood and deliver oxygen to cells. This results in less strain on the heart. Adequate hydration helps blood flow smoothly, reducing the risk of clots and related complications.

Water is a very underrated player in the fight against cardiovascular disease. 

Strengthens the Immune System

Adequate hydration aids in removing harmful substances that can weaken immunity. Water also helps the lymphatic system circulate immune cells and fight infections effectively.

Proper hydration also keeps the mucous membranes in the respiratory and digestive tracts moist, creating a barrier against pathogens.

Reduces Risk of Chronic Diseases

Proper hydration helps regulate blood sugar levels and prevents dehydration-related spikes. As a result, it plays a role in lowering the risk of diabetes complications.

Regular water intake helps maintain optimal blood pressure, which as already discussed, plays a role in reducing cardiovascular risks.

Water keeps joints lubricated, reducing wear and tear and lowering the risk of arthritis. A lot of joint issues can be improved by simply drinking more water. 

Longevity and Mortality

Whenever we discuss the health benefits or effects of anything, we can’t just look at them in isolation. We have to actually relate it back to whether or not the intervention or thing actually improves longevity or decreases the risk of mortality in a significant way. 

It is pretty obvious that drinking sufficient water improves your quality of life, as even mild dehydration decreases your energy and ability to perform. So even if drinking sufficient water didn’t increase your lifespan, it is still a beneficial thing.

However, drinking sufficient water does generally result in a lower mortality risk and increased longevity. So you really are getting the best of both worlds here; improved quality and quantity of life. All you have to do is drink enough water. So how much water should you drink?

How Much Water Do You Really Need?

There are a number of factors that go into how much water you need to drink each day. You see, you lose water through your urine, sweat, breathing, and bowel movements. These (to varying degrees) in turn are influenced by your activity level, the climate you live in, your diet, and your overall health status. 

So, you have to drink sufficient water to keep your overall water balance in a good place. But much like everything else to do with nutrition and human health, there is a Goldilocks Zone. You don’t want to drink too little, and you don’t want to drink too much. 

We want to avoid dehydration and overhydration.

Dehydration

Dehydration occurs when the body loses more water than it takes in, disrupting normal physiological functions. It can be classified into acute (short-term) and chronic (long-term) dehydration, each with specific consequences.

Acute Dehydration 

Acute dehydration is potentially very dangerous. You can die in a very short time without sufficient water. On average, a person can live without water for about 3 to 7 days, but this is a general estimate and not a hard rule.

There are a variety of symptoms associated with acute dehydration, such as: 

• Fatigue: A lack of sufficient water can reduce blood volume, making it harder for oxygen and nutrients to reach cells, leading to tiredness.
• Dizziness: Dehydration can lower blood pressure and decrease blood flow to the brain, causing lightheadedness.
• Headaches: Water deprivation may cause the brain to temporarily shrink slightly, pulling away from the skull and triggering pain receptors.
• Dry mouth and skin: Reduced saliva production and moisture levels result from inadequate hydration.
• Dark urine and decreased output: Indicators of insufficient fluid intake, as the kidneys conserve water during dehydration.

If this is allowed to continue, you will eventually get much worse and potentially die. 

Chronic Dehydration 

You can also be chronically dehydrated. This is where you aren’t drinking enough water over a longer period of time. There are a variety of issues associated with this, and these are generally more pertinent to this discussion as a lot of people aren’t consistently consuming enough water.

Some of the issues associated with chronic dehydration are:

Kidney Stones and Urinary Tract Infections (UTIs):

• Persistent dehydration can lead to concentrated urine, increasing the likelihood of crystal formation (stones).
• Insufficient water intake can also impede the flushing of bacteria from the urinary tract, raising UTI risk.

Digestive Issues:

• Chronic dehydration can slow digestion, contributing to constipation and other gastrointestinal disturbances.

Cardiovascular Stress:

• Over time, reduced blood volume due to dehydration can strain the heart, impacting cardiovascular health.

Skin and Aging:

• Prolonged dehydration may result in loss of skin elasticity, making the skin appear dull and more prone to wrinkles.

Performance and Cognitive Impairments:

• Physical Performance:
  • Even mild dehydration (a loss of 1-2% of body weight in water) can impair physical endurance, strength, and thermoregulation.
  • Reduced hydration can lead to muscle cramps and slower recovery times.
• Cognitive Function:
  • Dehydration affects focus, memory, and decision-making.
  • Dehydration is linked to slower reaction times and reduced problem-solving skills.

So, when we are deciding how much water to drink, we need to at least aim to prevent dehydration and experiencing these symptoms. But you can actually consume too much water. 

Overhydration and Water Intoxication

While hydration is essential, excessive water intake can also have adverse effects, known as overhydration or water intoxication. The most common issue that occurs when you consume too much water is a condition called hyponatremia.

Hyponatremia occurs when excessive water dilutes the sodium levels in the bloodstream, disrupting the balance of electrolytes. This imbalance can cause swelling in cells, leading to symptoms such as nausea, confusion, muscle cramps, seizures, and in severe cases, coma or death.

It is actually quite difficult to drink too much water, although it can happen when you drink large amounts of water in a short period without allowing the body to process and excrete it. This can often happen in endurance athletes or individuals doing stuff like water drinking competitions. 

The issue can be exacerbated when water intake isn’t balanced with electrolytes (e.g., sodium and potassium). 

Ok, so hopefully you see that you can drink too little and too much. So, how much water should you drink? 

Unfortunately, like most things related to nutrition, the answer isn’t straightforward. You see, there is an amount of water you need to drink to survive, and then there is an amount of water you need to drink to thrive. 

These numbers are also individual, so a generic recommendation really isn’t all that helpful, except as a starting point to start the process of individualising and dialling in on an amount that fits your unique needs. but with that in mind, we can begin this discussion around how much water you need to drink per day.

How much water do we need to survive?

Let’s deal with this question first, as it at least sets a baseline. Now, you would think that because water is so vital to life, we would have some very, very clear knowledge of how much we should be drinking to avoid, well, dying. However, we simply don’t. 

We do have some research to help us make an educated guess, but we simply don’t have a clearly defined figure as to exactly how much water any individual needs to drink at a minimum. However, we can still make some educated guesses. But do keep in mind that the figures are estimations at best, and we will refine them further, later on in this article.

A lot of work has been done by the World Health Organisation (WHO) on trying to establish an estimated average requirement (EAR) or a recommended dietary allowance (RDA), however, they simply couldn’t establish a concrete figure. 

This is something that is very important to them, as they are trying to set recommendations for the world, which does include areas where water intake is very low and death due to dehydration is frequent. Even with it being that important, they still don’t have concrete figures for the exact needs. 

However, the WHO has provided an adequate intake (AI) for health populations (this is set for North Americans). This AI is set as 3.7L per day for males and 2.7L per day for females. The WHO does further refine this and states that for a sedentary female adult, 2.2L of water is the bare minimum and for a sedentary male adult, the bare minimum is 2.9L per day. Both of these recommendations go up to 4.5L per day for active populations. 

These numbers are based on a 58kg female and a 70kg male. So naturally, if you are bigger than these values, your water intake will be higher, and if you are smaller than these values, your water intake will likely be lower.

Now, even the casual observer will probably realise that they know quite a few people, perhaps even themselves, who simply don’t drink this much water. Well, these individuals are probably chronically mildly dehydrated. They may not be in very severe ill health as a result, but they are likely not functioning at 100%. 

However, we must also factor in water is not only consumed by drinking it. About 20% of water intake comes from food. This is obviously different depending on the exact composition of your food (further elaborated later in this article). This is very intuitive once it is pointed out, as you may not be drinking 4L of water per day, but the fact you eat 5-12 fruits and vegetables per day is likely contributing over 750mL of water to your body per day. Not to mention all the water content in the other foods you consume. 

However, as diets can be so variable, it likely is a good general recommendation to at least consume the minimum water requirements from water itself (or fluids in general).

There is some research that ties how much water you need to drink to your caloric intake, which does have many positives as a benchmark. The Food and Nutrition Board (FNB) was tasked with setting water intakes for the US National Defence Forces, and this was later applied to civilian populations. Initially, they set the intake as 1mL per calorie (kcal), but have since revised that up to 1.5ml per calorie (kcal). However, neither should be viewed as the minimum value, but they can be used to further refine our recommendations.

Now, while the lower limit of water intake is definitely good to know, what most of us are really interested in is, how much water should you drink for optimal health, performance and body composition.

How much water do we need to thrive?

To dial in on this number, we must understand some of the variables that go into our body’s water needs. Some of these are obvious, while others are only obvious once they are pointed out.

The first thing that goes into deciding how much water you need is how much you sweat. If you sweat more, you are naturally losing more water from your body, and as a result, your water intake will need to be higher. 

It is fairly easy for people to understand, as sweat looks like water, and thus you can easily correlate water loss through sweating and an increased need for water. However, most people are actually awful at estimating just how much water loss has occurred due to sweating. This is especially true if you don’t exactly feel like you are sweating, and aren’t overheating. 

This is very prevalent in cold climates, especially extremely cold climates. You very often hear stories of people getting severely dehydrated when they go skiing. They don’t feel like they are excessively sweating because it is quite cold out, but they are actually sweating a lot. 

This also occurs in very hot climates where the heat evaporates your sweat very quickly, and you don’t actually experience a lot of actual sweat droplets occurring. It also occurs when the sun is beating down, but there is a nice cooling breeze. 

Basically, people can be very easily deceived in deciding their water intake based purely on how heavy they are sweating. It does bear mentioning at this stage that sweat isn’t just water, and it does contain quite a lot of other things (waste products and electrolytes). While having electrolytes in your water is generally good advice, it is especially good advice for those who are trying to replenish hydration levels after sweating. You are not only losing water, you are also losing these salts. Both need to be replenished.

Now, it is not only the environment that makes you sweat, as you may be well aware, exercising generally leads to an increase in sweat output. You also generally end up breathing at an increased pace, which leads to more water loss through water vapour loss in your breath. This is obviously dependent on the exact type of exercise you do, and we could get into some very specific details about how the exact exercise modality influences water loss, but this simply isn’t necessary. 

You just need to know that exercise generally leads to an increase in sweat output and thus an increased demand for water intake. Very generally, the higher intensity or higher volume you do, the more demand that occurs. 

There is generally less sweat output when doing lower-intensity activities, unless you start going for longer periods of time. So if you do something at a rating of perceived exertion (RPE) of 5 out of 10, and do one set, well it isn’t likely that you will be sweating a lot. However, if you do 50 sets of it, well, you will probably end up sweating. You will probably end up sweating more if those sets are done closer together (low rest periods). 

This also applies to cardiovascular activities. If you do a low-intensity recovery jog that barely gets your heart rate above 100 bpm, well, it isn’t likely that you will be sweating excessively. However, as intensity picks up (i.e. you go harder), so does sweat output. If you go for a 10-hour “recovery” pace jog, you will also likely end up sweating a fair bit. 

This is fairly intuitive as most people have sweated in response to exercise and understand the dynamics at play here. However, while most people are aware of it, quite often people forget to account for it in their daily water intake, and this can hamper short and long-term recovery from exercise, and even performance while exercising.

The next thing that influences water needs is body size. This should be fairly obvious, as it does generally correlate quite well with most nutritional wisdom and people’s daily life experiences. If you weigh ~100kg your water needs are, naturally enough, going to be different than those of someone who weighs ~60kg. 

Generally, the bigger you are, the more water you need. This is fairly intuitive, as you simply have more cells, and more blood volume, and you also have a larger surface area if you are bigger. However, related to the surface area and water, which is slightly less intuitive, you are able to better regulate your body temperature if you are bigger. This is why in polar regions where temperatures are very cold, animals get very large. They are able to keep their core temperatures high because they have bigger bodies. A larger surface area allows you to cool off more quickly through sweating too, as you can sweat more and have it evaporate, thus cooling you. This does, however, lead to an increased need for water. 

While that is a bit esoteric, it does impact the real-world experiences of everyday people. If you lose a significant amount of body weight, let’s say you lose 10kg of fat on a fat loss diet over 12 weeks. You will likely be colder in general. However, compounding this is the fact that you likely also experience metabolic adaptations that lead to an increased metabolic efficiency, which likely means you generate less heat waste. 

So your water needs are tied to body size, but also metabolism, and thus there is a temporal dimension to discussing water needs. Someone who has bulked up to 100kg, and someone who has dieted down to 100kg may have different water needs due to slight differences in their metabolism. However, while this is important to know, it likely isn’t a huge magnitude of effect. But it does bring us nicely to our next point.

The overall diet does influence your water needs. This applies to both the caloric contribution of the diet, but also the macronutrient composition of the diet. The discussion is hard to fully elaborate on, as so many things are intertwined, such as calorie intake generally being higher in larger individuals. 

This makes it hard to truly disentangle whether a higher water intake is needed because of more calories (a proxy for metabolic rate), or simply because of a bigger body size. Activity levels could also be very high, leading to higher calorie demands, but also higher water output (sweat). So it is hard to say exactly which is the contributor to higher water demands, the higher calories or the higher output, and if they have different contributions, then it gets very messy very quickly. 

However, as a very general rule, you can assume that calorie and water intake are intrinsically tied as a baseline. This does influence our recommendations, so do keep in mind that this is an underlying assumption. It will mean that our recommendations will need to be tweaked for the individual, but that is the case with all recommendations. 

Now, while calorie intake is tied to water needs, the exact composition of those calories must also be accounted for. Depending on how much protein, carbs, fats and fibre you eat, your water demands are likely to be different. 

If you are following the general dietary recommendations we have been discussing in this article series so far, then we can assume that protein intake is fairly standardised. So we won’t consider it in this discussion. However, if someone is eating a low-protein or extremely high-protein diet, then water needs are likely slightly different. 

If someone is eating a higher fat diet, the water needs may be higher, as you generally won’t be eating a lot of foods that have a high water content. 

If someone has a high-fibre diet, they may need less water because they are generally eating foods (i.e. vegetables and fruits) with a high water content. 

This is also generally true of carbs, but they do also lead to the retention of more water (this is in the muscles so it is generally a good thing), so they do potentially delay dehydration. This may mean that you can get away with a lower water intake on a given day, if the diet has generally been high in carbs and general water intake has been good. 

There are also likely many confounders to this, and it is poorly explored in the research, but it does bear keeping in mind that the exact type of diet eaten does influence water needs. However, this information doesn’t influence our generic starting point for water recommendations and only gives you some information as to the “why” behind the need to tweak this recommendation for your exact situation.

Finally, water needs are influenced by both individual genetics and individual health demands/needs. There isn’t much you can do about the genetic component, and while it does influence things, it is a very individual thing. Of course, we can make some broad assumptions on a population basis, but it still needs to be tweaked to the individual. 

For example, if your ancestors have survived in a desert environment for millennia, then you may have specific adaptations that allow you to get away with lower intakes of water. 

While making assumptions based on ancestry is a good starting point, it doesn’t tell the whole story, and you may be the “unlucky” individual who would have died in that environment because the beneficial genes in that environment “skipped” you. So it is a good starting point, but it doesn’t tell the whole story, you still need to tweak for your exact situation and needs. 

This is also true if there is a family history of disease, especially diseases related to organs/systems that rely heavily on water for their function, such as the kidneys. So if you know that there is a history of kidney disease in your family, it would definitely be a wise move to engage in practices that help with kidney function (such as drinking enough water). So you may just always err on the side of “too much” water rather than “too little” in hopes of staving off disease. 

However, while this is a good starting assumption, a family history of disease doesn’t mean you certainly will get it. But it does bear keeping family history of disease in mind whenever you are looking to design diet and lifestyle practices.

Ok, so let’s answer the question; how much water should you be drinking?

How Much Water Should You Drink

I am going to give you two answers. The first is a very practical one that allows you to refine the second recommendation, which is more tied to what we have discussed above.

A rough rule of thumb for how much water you should drink per day is that you should have 5 clear urinations per day. If you are exercising that day, at least two of them should be after the workout (and ideally, at least 1 clear urination before/during the workout, to ensure you are actually hydrated during the workout). 

However, while this rough rule of thumb is practical, it doesn’t necessarily give us a starting point. Instead, it gives us a practical real-world measuring point to potentially refine our intake against.

So what can we use as a starting point for how much water we should drink?

Well, for very rough and ready figures, I generally recommend two values be used and see how they line up together. The first figure I use is recommending 40mL of water per kilogram of body weight. 

This does take into account a lot of the concerns around what goes into deciding water intake, as it is based on your body size. However, I generally also compare it against a water recommendation based on calorie intake, as weight is only a proxy for caloric intake (and thus metabolism). So I refer back to the 1.5 mL per calorie (kcal) recommendation outlined above. 

This allows me to get a better idea of where water intake should be, and oftentimes, one recommendation will be higher or lower than the other and seeing this allows me to make better recommendations ahead of time. 

It isn’t simply a matter of picking the higher number though, we want to first look at why the two numbers don’t perfectly line up. Generally, it will be due to exercise/non-exercise activity. Someone may only weigh 70kg, but they may have a very manual job which brings their calorie needs much higher. So we would choose closer to the 1.5mL per calorie (kcal) in this case.

However, we may actually recommend beyond that, as they are very active and this is especially true if the work environment is also very hot and sweating is heavy. So while we might set the intake at 1.5mL per calorie (kcal), we would use the 5 clear urinations per day rule to get an estimation as to how effective this has been as a hydration strategy. 

It should be noted that this refinement strategy of 5 clear urinations per day can be hard to follow if you are taking a multi-vitamin, especially if it is a more than once per day multivitamin, as it will likely make your urine more yellow than it otherwise would be.

It does also bear pointing out that, despite what some people say, all liquids including coffee will help with hydration to some extent, with the exception of alcohol. These other liquids can be included in the target, and we will discuss this in a moment. 

Food does also contribute, but from a practical perspective, I don’t include this in the target. Unless you are squeezing all the water out before you eat it, or figuring out how much water was added/lost due to cooking methods, it simply isn’t practical to include it. But it is a good idea to be aware that the diet does contribute to how much water you consume per day.

Finally, you do also want to be aware that as water intakes climb, you do want to be mindful of electrolytes. This is important for those who require very high intakes due to high activity levels and may also be sweating quite a lot.

Can I just use thirst to dictate how much water I should be drinking?

Simply put, no, thirst is not a great metric to dictate how much water you should drink. It would be like only using hunger to dictate calorie intake. While yeah, the two things are intrinsically related (hunger and food intake, and also thirst and water intake), they are not a perfectly calibrated system. 

If people were good at listening to hunger cues, we simply wouldn’t have an obesity epidemic. So while using thirst as a guide is a good strategy to prevent severe dehydration, it is not a great strategy for those looking to maximise their health and performance. You don’t notice you are thirsty until you are already dehydrated, and thus already compromising your health and performance. 

This is especially important if you are really pushing performance metrics (i.e. you are an athlete or really trying to increase training performance), you should most definitely be pre-emptively hydrating. Infants and the elderly are also very poor at letting thirst guide their water intake. So planned intake and pre-emptive hydration is generally a better strategy than letting thirst guide hydration, although once good systems are put in place, less focus is needed to ensure water intake is sufficient.

How Much Water Should You Drink Summary

So, we covered a lot there. The question is quite straightforward, however, surprisingly, for such a vital question, we don’t actually have as concrete a minimum figure as we would like. However, we do have enough practical data to make some fairly good recommendations, and we also have practical methods of refining our intake to achieve a level of water intake that leads to our best health, performance and body composition. 

As a baseline, a relatively unrefined water recommendation for men is 2.9L per day and for women 2.2L per day. This is a rough bare minimum, and if you are consuming less than this, well, you want to start consuming more as soon as possible. 

A more refined intake that can then be personalised is between the following two recommendations, consume between 40mL of water per kilogram of body weight and 1.5mL per calorie (kcal). 

You can choose whichever number you wish to start, and then you can refine your intake so that you urinate 5 clear urinations per day. You also want to potentially look at electrolyte consumption too, but we will touch on that in future lessons.

Quick Summary: Consume somewhere around 40mL of water per kg or 1.5mL of water per calorie, and refine this intake and distribution so that you are urinating relatively clear ~5+ times per day.

Water Distribution

I am including this in the discussion because as mentioned previously, water could be considered a macronutrient and a lot of people just kind of ignore it. Similarly to the general recommendations, we just want to space our water intake out relatively evenly across the day. 

We generally recommend people aim to consume enough water across the day so that they have >5 urinations per day, with at least 3 of them being clear(er). Ideally, we would prioritise water intake before during and after workouts too, and we generally recommend having clear urinations before/during/after your workouts as a marker of good water intake and distribution. 

I personally like to recommend about one-third to one-half of daily water needs consumed around the workout. If the sedentary water needs are roughly 2.5L and due to exercise, the needs go up to 4.5L (or more), then it makes sense to consume that extra water around the event that is increasing the water needs. While that is fairly intuitive, naturally there are limitations and considerations when trying to actually put this into practice.

You don’t have to obsess over this, but it does make a lot of sense to just drink water fairly evenly across the day if you want to ensure you are well hydrated across the day. Something that can help with this is having a water bottle that you bring with you wherever you go. 

Another habit that can help is to aim to drink 250-500mL of water first thing in the morning. I don’t mean you need to gulp this down the morning you wake up, but as you are likely to wake up mildly dehydrated from not consuming water overnight and sweating all night, it makes sense to rehydrate first thing. 

Some people do find that they need to taper their water intake off closer to bed, as drinking too close to bed can cause them to wake up during the night needing to urinate. So while we recommend a relatively even spread across the day, you could argue that biasing your intake earlier in the day and then similarly to not eating in the 2-3 hours before bed, you want to reduce your water intake the closer you get to your bedtime. 

Water Sources

While we generally discuss hydration in relation to water intake, there are actually many sources of water in the diet that aren’t actually purely water that do significantly contribute to your water intake. Now, there are an incredible amount of sources of water in the diet, and I simply am not going to list them all here. However, I do want to mention a few frequent ones.

The first other source of water in the diet is carbonated water. This is pretty much the same as normal water, except it has been carbonated. I only mention it because people will often wonder about it in particular when discussing water sources. 

Carbonated water does have some unique properties, such as potentially helping heart health and lipid profile. It does also anecdotally increase fullness (thus potentially allowing you to eat lower calories, though it may increase gherlin, thus potentially leading to higher calorie intake due to increased hunger). 

It is often claimed that carbonated water will cause tooth decay, but you would have to basically hold the water in your mouth for this to occur and even then saliva likely prevents tooth decay from occurring by this mechanism. There is also the claim that carbonated water leads to bone mineral loss, but there is no real evidence for this.

Related to this is the consumption of soft drinks. These are basically carbonated water that is sweetened with either artificial sweeteners or sugar, along with flavourings. These do contribute to hydration, although the sugar-containing ones likely aren’t great for your calorie management or tooth health. 

The sugar-free ones are better, but to use either as your main source of hydration likely isn’t a great idea. I would argue that these do contribute to hydration, but as a general practice, I simply wouldn’t count these towards your water intake needs. 

You can certainly top up your water intake with a soft drink, but I wouldn’t make it a daily practice. They do contribute to hydration, but I would definitely categorise these lower down in water quality and try to prioritise water intake over these. However, they do contribute to hydration, so if you really wanted to, you could count soft drinks towards your water intake.

Related to this is the use of artificial flavourings in water. These are generally pretty much 99% water, so they can functionally be treated as normal water. Now, of course, you do have to look at them individually, as there may be artificial flavourings or additives that you personally see as detrimental to health, or that you don’t want to include in the diet for whatever reason.

The next commonly asked about liquids are coffee and tea. Now, while there is quite a lot of information floating around out there that says these do actually cause dehydration, there simply is no actual data to suggest that when looking at actual hydration. 

While people have generated a multitude of mechanisms by which caffeinated beverages cause dehydration, the real-world data does not support this. So you can likely count your tea and coffee towards your hydration goals, however, I would still generally recommend that you prioritise water over these.

The next source of water in some people’s diets comes from fruit juices. These can be either homemade fruit juices or store-bought fruit juices. These fruit juices are mainly water, and thus do contribute to hydration. 

They are actually generally quite a good source of hydration as they generally contain electrolytes and some form of sugar, which all lead to better hydration qualities. So fruit juices do qualify as a higher water quality source, however, we do have to balance the hydrating benefits with the fact that you are effectively just drinking calories. 

So if purely hydration is considered, fruit juices can be very beneficial. However, for most people, adding extra calories to their diet in the form of a low-satiety foodstuff doesn’t generally lead to better health or body composition outcomes.

While most people don’t tend to think of this, the food you eat does also contain water (depending on what exactly you are eating and how it was cooked/prepared). So the food you eat may be contributing to your hydration status. 

This is especially true of very high water content foods such as fruit and vegetables. These foodstuffs are generally very high in water content and also high in electrolytes/minerals, which results in better hydration. 

Some starchy carbohydrates can also significantly contribute to hydration depending on how they are cooked. You can seriously hydrate noodles, pasta, rice or oats by leaving them for longer to cook in water. 

The water content of the food you eat definitely contributes to hydration, however, it is extremely hard to keep track of. For this reason, I tend to not count it in daily water intake, but I do take it into account when refining the water intake needs. If you are an individual who eats a lot of hydrated starchy carbs and lots of fruit and veg, and then you try to drink the top end of the recommendation, you may notice you are urinating clear very frequently. You may wish to just dial back on your actual water intake and chalk it up to your fruit and veg intake contributing to your hydration.

Finally, milk is another source of hydration in the diet. Milk has quite a few properties that make it an excellent hydrating liquid, such as the carbohydrate content and the electrolyte/mineral content. However, as with juices, you do have to factor in the calorie and macronutrient content into the equation. 

Drinking 4.5L of milk per day to reach your hydration needs is likely going to contribute an excessive amount of calories to your diet. But other than the fact that you have to factor in the calories/macros, milk is an excellent hydration tool, except of course if you are lactose intolerant. You could make a strong argument that drinking milk post-workout is one of the best post-workout drinks, as it is an excellent rehydration tool, as well as being a nice hit of protein and carbohydrates.

Now, it bears mentioning here that alcohol is not a hydration tool, as it does actually cause dehydration. We will be discussing alcohol in later lessons, so I am not going to say too much here, except that I simply would not even consider alcohol intake in water intake goals, even if you are using some other high water content liquid as a mixer. I am not going to try and even calculate the exact amount of dehydration that occurs, as then suggest you drink that much extra water or other liquid, as I simply don’t think you should be including alcohol in a conversation about water intake. I only mention it because you will occasionally see people ask questions about their alcohol intake and how it fits in with hydration.

How Much Water Should You Drink Conclusion

Hopefully that all has helped you better answer the question of how much water you should drink. I do know that a lot of people are very often surprised at just how much water they should be drinking. But once you get into the habit of drinking enough water, you really do see the benefits. 

Dietary change does just take some time and effort. If you need help with this, you can always reach out to us and get online coaching, or alternatively, you can interact with our free content.

If you want more free information on nutrition, you can follow us on Instagram, YouTube or listen to the podcast, where we discuss all the little intricacies of exercise and nutrition. You can always stay up to date with our latest content by subscribing to our newsletter.

Finally, if you want to learn how to coach nutrition, then consider our Nutrition Coach Certification course, and if you want to learn to get better at exercise program design, then consider our course on exercise program design. We do have other courses available too. If you don’t understand something, or you just need clarification, you can always reach out to us on Instagram or via email.

Paddy Farrell

www.triagemethod.com

Hey, I'm Paddy!

I am a coach who loves to help people master their health and fitness. I am a personal trainer, strength and conditioning coach, and I have a degree in Biochemistry and Biomolecular Science. I have been coaching people for over 10 years now.

When I grew up, you couldn't find great health and fitness information, and you still can't really. So my content aims to solve that!

I enjoy training in the gym, doing martial arts and hiking in the mountains (around Europe, mainly). I am also an avid reader of history, politics and science. When I am not in the mountains, exercising or reading, you will likely find me in a museum.