Having 8 Glasses Of Water Daily Could Be Too Much, According To A Study

Water is life — covering more than 70% of the Earth's surface (via USGS); water is a reason why no other planets (that we know of) in our solar system can support life, per MIT. It can be found underground, in the oceans, in the atmosphere, and in our very own bodies. Every single lifeform depends on water for survival; humans themselves can't go more than a few days without it, according to Business Insider. Composing about 60% of our bodies, it's easy to understand how vital water is to our health. Exactly how much you need, however, is a subject that's up for debate. As it turns out, there's no "one size fits all" approach to your daily water intake.

For what seems like forever, the majority of us have blindly accepted the rule of drinking eight glasses of water per day — a number that has no scientific merit, according to a statement from Yosuke Yamada of the National Institute of Biomedical Innovation, Health and Nutrition in Japan (via The Guardian). A 2022 study published in Science suggests that eight glasses are actually excessive for most people, and although it's not likely to have a negative impact on your health, it's a well-known fact that water is an increasingly limited resource. As the world's supply becomes more and more scarce, how much water you consume today could have a greater impact than you realize tomorrow.

A personalized approach

Every cell, tissue, and organ in our body needs water in order to function — the exact amount of it, however, varies widely from person to person, according to Mayo Clinic. A 2022 study in Science, which was authored by over 80 biological and environmental experts, found that prior research often left out two major variables: the water content of food and water turnover, or how much water the body uses each day (via The Guardian).

The new research suggests that most people only need about 1.5 to 1.8 liters of water a day, the equivalent of 6 to 7 cups. However, if you're eating foods like fruit, vegetables, meat, fish, rice, and even pasta, you could already be achieving half that. Additionally, if your water turnover rate is normal — in the case that you're not actively exercising, pregnant, in a hot or humid environment, or sick (per Mayo Clinic) — drinking extra isn't necessary. Most healthy people can stick to drinking water when they're thirsty and increase their intake as needed.

In reference to the eight-glass rule, professor and co-author John Speakman told The Guardian, "I think it's a recommendation that many people just ignore and follow what their body is telling them." He went on to say, "If 40 million adults in the U.K. were following the guidelines and they drunk half a liter of clean water more than they need each day that's 20m liters [5 million gallons] of wasted water every day."