Is Drinking Eight Cups of Water Daily Really Necessary?

While most people have heard that it is important to drink eight glasses of water each day, it is quite unclear where this notion came from.

According to Science Alert, the evidence for this notion has been debunked over time. Studies that measure water intake also use retroactivity to gauge how much water the individual drank. This method generates self-reports that have poor accuracy and precision.

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How Much Water Do People Really Need?

To more accurately gauge how much water people need, a new study published in Science covered a sample of more than 5,600 individuals of different ages and from 26 different nations across the globe.

As part of the study, participants were given 100ml worth of water filled with 5% doubly labeled water, which is usually used in experiments involving metabolism because it allows the monitoring of the speed of chemical movement within the body. Such type of water is filled with hydrogen isotopes known as deuterium. They are also armed with an additional neutron inside their nucleus, making them twice the weight of regular hydrogen atoms.

This water was 10% heavier compared to regular water. Nevertheless, it is safe to take in minimal quantities.

Moreover, to make the water doubly labeled, the water is also blended together with water that has an oxygen isotope. Oxygen-18 contains ten neutrons and 8 protons within each atom.

This oxygen is generally stable and natural, comprising 0.2% of the air people breathe in and out.

Nutrition scientist Dale Schoeller, who was also a proponent of the study, mentioned that if one spends a week examining the rate of eliminating isotopes that are stable through urine, the isotope of hydrogen can relay the amount of water that is replaced. Moreover, eliminating the oxygen isotope can also relay the calorie amount that is being shed out.

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Water Requirements Vary

According to this recent study, the team showed that daily water intake largely depends on activity levels, gender, age, and climate. Simply stated, the requirements vary depending on certain lifestyle and environmental factors.

Science Alert notes how the researchers expressed that there is no one-size-fits-all regarding water intake. They further stated that the popular suggestion that drinking eight cups of eight-ounce water daily does not have any objective basis.

Water Turnover Rates

The University of Wisconsin-Madison notes that rates for water turnover were highest for men who joined the study in their 20s. Women, on the other hand, plateaued from twenty years old up to fifty-five years old.

The highest turnover rate was found in newborns, with around 28% of water replaced daily.

Differences in athletic status and physical activity could largely explain these differences in water turnover rates. Sex came in second to this first factor.

The researchers also found out that those from countries with low Human Development Index had more water flow through them within a day.

Yosuke Yamada, one of the researchers involved in the study, noted how it is increasingly important to quantify the water consumption of humans because of climate change and the rising population. He mentions that because water turnover is directly related to other significant facets of health, such as body fat percentage, this figure can become a biomarker or indicator of one's metabolic health.