It’s estimated that on average, approximately 60% of the human body is made up of water.
There is general agreement across health professionals, scientists, nutritionists and those in sports medicine that it’s important to stay hydrated and have a healthy daily water intake.
However, there isn’t always consensus on what that proper water intake is, and there are often differing opinions on the question “how much water should you drink a day”?
This article will look at the benefits of drinking water, what happens if you don’t get enough daily fluid intake, and will end with some guidance on how much water you should be drinking each day.
Why do we need to drink water?
Keeping properly hydrated is important for good health, and keeping every system in the body functioning properly.
Some of the functions of the body that water helps with include:
- regulating body temperature
- helping with digestion
- preventing constipation
- maintaining sodium balance
- carrying nutrients through your body
- normalising blood pressure
Staying sufficiently hydrated also has other benefits:
- increased energy levels
- performing better during your workouts.
- reduces muscle cramps and soreness post-exercise
- it can help you control your appetite and maintain a healthy body weight
- it can help prevent dry skin.
What happens if you don’t drink enough water?
Your body loses water when you breathe, sweat, and digest food. So it’s important to drink fluids and eat foods that contain water to rehydrate.
If you’re losing more fluids than you are consuming, you are likely to become dehydrated.
There was a 2016 study in the American Journal of Clinical Nutrition, titled “Minor degree of hypohydration adversely influences cognition” which found that a loss of less than 1% of body mass due to dehydration resulted in poorer memory, poorer attention, and a perceived decline in energy.
So even mild dehydration can have an impact on how you experience daily life and your fitness training routine.
Some of the symptoms of dehydration to stay aware of include:
- dry mouth
- bad breath
- feeling lethargic
- dry or flushed skin
- headaches
However, possibly two of the simplest measures of whether you’re sufficiently hydrated or not are if you’re feeling thirsty, and the colour of your urine.
Our bodies are wonderful things, and their natural indication that you might not be getting as much fluid as you need is to trigger a feeling of thirst. So if you listen to your body and drink when you’re thirsty, this is likely to be a good way to prevent dehydration.
It’s also worthwhile checking the colour of your urine when you visit the bathroom. If you’re sufficiently hydrated, your urine should be light yellow in colour. If your urine is clear it’s a sign that you may potentially be drinking too much. If it’s darker yellow, this is a sign you potentially need to increase your fluid intake.
How much water should you drink per day
Some experts suggest that broad guidelines on target water consumption aren’t really that useful, and that we don’t need more fluid than our bodies signal for when they ask for it through thirst.
It’s worth noting that many of the current guidelines for daily water intake were based on advice published in 1945 by the US Food and Nutrition Board, which suggested that people should try and consume 1 millilitre of liquid for every calorie of food they consumed.
So if we assume that a typical daily calorie intake is between 2000 and 2500 calories, this would lead us to a recommended guideline of between 2 litres and 2.5 litres of liquid per day.
However, part of the 1945 advice that is often misunderstood is that liquid can be obtained from other drinks (not just plain water) and also from fresh fruit and vegetables.
It’s also important to note that every individual’s needs are different, and the amount of water they need to stay hydrated and healthy is likely to depend on their age, weight, activity levels and any underlying health conditions.
So what about the guidance on drinking 2 litres of water per day?
The origins of the idea of consuming 2 litres of fluid per day for optimal health benefits dates back to this guidance originally published in 1945.
So if we were following the 1945 study, the ‘two-litre’ guidance is broadly correct, but it’s important to understand that your fluid intake can come from a variety of sources – not just water.
If anyone was drinking water at around 2 litres per day, in addition to fluid from other sources, they are unlikely to be doing themselves any harm.
However, it’s important to monitor your urine and overall health to make sure you’re not drinking too much water.
How many glasses of water per day – What is the guidance?
This is really just a rehashed version of the ‘2 litres’ guidelines, but arguably a little more accurate in the spirit of the original 1945 guidance.
This guidance is based on the fact that your typical drinking glass is approximately 8 ounces (236 millilitres)
If you drink between six and eight glasses of water per day, your water consumption will be anywhere between 1400ml and 1900ml, and you can assume that additional fluid will be consumed from fruits, vegetables and other beverages.
Will I need to drink more water if I exercise?
As a general rule, if you’re sweating then you need to be consuming more liquid than you would usually.
So if you’re exercising to a level that you’re breaking a sweat, your fluid loss is higher, and you should factor this into your fluid intake, to make sure you get enough water.
It’s also worth bearing this in mind during hot weather that causes perspiration. If you’re sweating, you’re likely to need a little more water than usual.
However, it’s sometimes easy to overestimate how much we’re actually sweating and how much additional water we need. Self-moderation and trusting your natural indicators (thirst, colour of urine) are key.
Do I have to drink plain water? Or do other drinks count?
In addition to plain drinking water, your recommended daily fluid intake can come from other sources.
Other beverages such as sparkling water, lower-fat milk, sugar-free drinks, fruit juice, sports drinks, and even caffeinated drinks such as tea and coffee count towards your daily fluid intake.
It’s also worth remembering that water-rich foods such as fresh fruit and vegetables also count.
Can you drink too much water?
Yes. If the colour of your urine is clear, and you’re making frequent trips to the bathroom it’s likely that you’re drinking a bit too much water.
The symptoms of mild overhydration (excess water in the body) are actually quite similar to that of dehydration:
- headaches
- tiredness or fatigue
- nausea
Cases of extreme overhydration can actually be really serious (even life-threatening) if it gets to a point where it dilutes the sodium levels in the blood.
So if you’re exerting yourself really hard with your training, always listen to your body, drink accordingly based on your sweat rate, avoid overdrinking, and consider if you need to take electrolyte tablets or other high sodium foods.
