There is a famous axiom that you should drink eight glasses of water every day or approximately 2 liters worth. Often, urban legends of this kind are created without any scientific basis or evidence. So it is with the myth of drinking two liters of water every day. In a book co-authored by leading nutritionist Dr. Fredrick Stare in 1947, he casually mentioned that the appropriate amount of water required is 6-8 glasses a day. There was no scientific basis for this and instead this was purely suggestive. Like every good story, it gained traction, and soon everyday people came to believe in the virtues of drinking sufficient water.
What does science say? Well, there is no single truth. The amount of water depends on your lifestyle and where you live. If you are very active, working out or have a lifestyle that keeps your outdoors in the sun, your requirement of water will be higher. If you are like many urban dwellers who spend a large part of their lives indoors in conditioned habitats, leading a sedentary lifestyle, your water requirement will be far less. Doctors believe that your body knows how much water you need and will regulate your need. This regulation is the process of homeostasis working for you.
Can you, therefore, end up drinking too much or too little? Creating toxicity with water is hard. However, too much water can dilute your electrolyte levels, which can have a detrimental effect on your nervous system. Too little can leave you dehydrated which can cause dizziness, low blood pressure, rapid heart rate, sleepiness, fatigue, headaches and also the inability to regulate your body temperature because of the failure to perspire.
You are therefore best served by creating a routine that ensures that your body is not short of water. Ultimately, your body knows best, but it does not hurt to help it along.