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Water is a basic unit of life. Without it, our body simply cannot function. Our body itself is about 60% water.

The body loses a lot of water, mainly through sweat and urine.

When it comes to the question of how much water should you drink a day, the answer can vary widely.

The most common recommendation is to drink a minimum of 2 liters (about 8 glasses) of water per day.

We call this the 8×8 rule, and it is very easy to follow.

How much water per day

Some “health experts” believe that the body loses so much water that you need to keep drinking water at every opportunity, even when you don’t feel thirsty.

Even though we get a lot of water from our foods and beverages, some still insist you drink at least 2 liters of pure water a day.

However, this is not necessary. Many scientists insist that the 2 liters a day figure should include water from all sources, including foods and beverages. Water makes up about 80% of all the beverages and drinks you take. So, if you drink a lot of coffee, tea, and other beverages, you do not need to stick to the 8 glasses of water rule.

However, how much water you need per day is largely based on several factors, both internal and external.

In our attempt to answer this question, we want to examine a few of the numerous studies on water and how it affects various function in the human body. At the end of this article, we believe you’ll be able to determine your daily water intake needs accurately.

Does Drinking More Water Boost Our Energy levels and Improve Brain Performance?

Some claim drinking plenty of water can boost energy levels and improve brain activity.

There are many studies on this subject, and a lot of these studies have found evidence to back these claims.

A study involving women measured the effects of fluid loss after a workout. It found that losing just 1.36% of fluids had a negative impact on mood and concentration. The women also experienced more headaches than usual (a).

Research also shows that losing about 1 to 3% of your body weight in fluids due to workouts can have a negative impact on brain functions (b, c, d).

However, most of us don’t lose 1% of our body weight in water. This can only happen during extreme heat or a high-intensity workout, where you can lose a huge amount of water through sweating.

Your level of physical performance can also drop due to mild dehydration (e, f, g).

Conclusion: There is evidence that mild dehydration (brought on by heat and exercise) can have a negative impact on mental and physical performance.

Can I Lose Weight by Drinking More Water?

Rumor has it that drinking plenty of water can have a positive impact on weight loss. It is said that it can boost your body’s metabolism and suppress appetite.

A study found that you can temporarily boost your metabolism by about 24 to 30% when you drink 500 ml of water (h).

The graph below shows how drinking 500ml of water can affect metabolism within the first 90 minutes.  Notice how 500 ml of water increases the EE (Energy Expenditure) value and then drops as you approach the 90 minutes’ mark (i).

effects of water on metabolism

Some scientists estimate that you can burn about 96 more calories per day if you drink 2 liters of water per day.

The maximize the energy expenditure, you should consider drinking cold water. This way, the body expends some of its energy in raising the temperature of the water.

Some studies show that you can eat fewer calories if you drink a glass of water about 30 minutes before meals. This works particularly well in the elderly (j, k).

Researchers found that some people on diets lost about 44% more weight over a 3-month period by drinking 500 ml of water before each meal (l).

In the end, it seems that water does have a positive effect on weight loss.  It seems that drinking plenty of water (especially about 30 minutes before meals) can cause significant weight loss over time.

Conclusion: Numerous studies show that one can lose weight if you drink water before meals. It helps boost metabolism and suppress appetite.

Does Drinking More Water Promote Good Health?

A few studies show that increasing your daily water intake may have a positive impact on a few health issues.

  • Research shows that your risk of bladder and colorectal cancer may significantly reduce if you drink plenty of water each day, but some other studies found no link (m, n, o, p).
  • Most of us have experienced constipation at some point, and it is not pleasant. Studies show that drinking more water can help prevent the problem (q, r, s).
  • Scientists also found that increased water intake can lower your risk of kidney stones (t, u).
  • You’ll come across plenty of testimonies on the internet that drinking plenty of water can have a positive effect on some skin conditions. There are claims it can hydrate the skin and help fight acne. However, we could not come across a single study that corroborates this claim.

Conclusion: Increased water intake may have beneficial effects on some health issues like kidney stones, cancer, and constipation.

Should You Count Other Fluid Intakes Towards Your Daily Total?

Pure water is not the only contributor to fluid balance in the body. There is plenty of water in other liquids and food we ingest.

As we mentioned in the first paragraph of this article, these fluids can also count towards how much water you should drink a day.

Some people claim that drinks like coffee and tea do not count because of their high caffeine content. They claim caffeine promotes urination, but this is a myth.

Research shows that although caffeine may be a diuretic (promote urination), the effect is significantly weak (v).

A lot of the foods we eat also contain plenty of water. Vegetables, fruits, fish, meat, eggs can contribute high volumes of water to our daily intake.

The fact is, if you drink a lot of coffee, tea, and other beverages throughout the day, then you are meeting a significant amount of the recommended 2 liters of water per day.

You, therefore, don’t need to drink 8 glasses of water, in addition to what you get from other sources if you don’t sweat a lot.

Conclusion: Water makes up most of the content of beverages and other drinks, and many of the foods we eat also contain plenty of water. These other sources of water should count towards your daily water intake provided you don’t sweat a lot.

Should I Drink Water Only When I’m Thirsty?

Water balance is critical to life.

Because of this, our body has developed a system to warn us when our water level becomes too low. It’s just like the system in your car that warns you when you are about to run out of fuel. If you ignore this warning, your car will eventually shut down, and this is the same for your body.

Thirst is the body’s low-water warning system. You feel thirsty when the water level in your body falls below a certain level.

It kicks in automatically without you having to think about it, just like how your body controls breathing.

This thirst warning is enough to keep most of us hydrated because we typically drink something to quench our thirst. This alone is enough to meet the daily water needs of most of us. The thirst warning is a very reliable way of regulating our water intake, and we should trust it (w).

Many people think the 8×8 rule is backed by science, but this is not true. It’s simply a widely-accepted rule that takes into account all your fluid intakes, including beverages and other drinks (x).

However, you may need to ignore the thirst warning in some situations and drink water even when you don’t feel thirsty.

This is particularly true if you sweat a lot. This includes sweating from intensive workouts and hot weather conditions (especially in dry climates).

Therefore, if you exercise, you should drink plenty of water during your routines to replace the fluids lost through sweating. The same goes for athletes. They need to replenish electrolyte levels in addition to lost water.

Nursing mothers also need to drink more water because of the water lost through breastfeeding.

You also need to drink plenty of water if you are suffering from illnesses like diarrhea and, and if you tend to vomit a lot.

Research shows that, as we get older, the thirst impulse may not work accurately in some people. Therefore, the elderly population needs to monitor their water intake closely (y).

Conclusion: Most of us don’t need to consciously control how much water we drink per day. The thirst impulse ensures that we stay hydrated if we listen to it. However, certain situations require some people to consciously monitor their water intake.

So How Much Water Should You Drink a Day?

The truth is, there is no simple answer to this question. As with this question about other things, this depends largely on the individual and many factors.

For most of us, we don’t need to monitor our water intake consciously. Drinking extra water may have benefits for some people, while for others, this only means a few extra trips to the bathroom.

Having said all that, I believe making a conscious effort to increase your daily water intake won’t hurt. The benefits may not be huge, but they are helpful all the same.

If you are worried about your water intake, you can follow the guideline below. It should satisfy the water needs of most people.

  • Drink a glass of water whenever you feel thirsty.
  • Stop drinking when you quench your thirst.
  • Increase your water intake during hot weather and exercise. In such situations, you don’t need to wait for the thirst impulse to kick in.
  • Keep water close by and take a sip occasionally.

If you follow everything we’ve written in this guide, you won’t have to worry about how much water you need to drink in a day.

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