More Koreans follow the ‘2 liters of water a day’ rule — but is it really necessary?
Park Chang-bum, professor of cardiology / Courtesy of Kyung Hee University Hospital at Gangdong
Water is essential for survival. While humans can live for up to three months without food, we cannot survive more than two to three days without water. That is because water in the body is continuously lost through various processes — roughly 1.6 liters a day through urine and feces, 0.6 liters through sweat and 0.4 liters through breathing.
Given these losses, how much water should we drink daily? Some experts argue that we must drink at least 2 liters of water daily. However, others say there is no strong evidence that drinking this much water provides significant health benefits.
A U.S. study published in 2002 tracked healthy adults aged 38 to 100 over six years. Participants who drank at least five cups of water daily (about 1.25 liters) had a 54 percent lower risk of heart disease among men and a 41 percent lower risk among women compared with those who consumed fewer than two cups (about 500 milliliters) per day.
However, more recent research contradicts those findings. A U.S. study that followed adults over the age of 25 for an average of 11.4 years compared two groups: those who drank around 4 liters per day (4.4 liters for men, 3.6 liters for women) and those who consumed about 2 liters or less (2.5 liters for men, 2.0 liters for women). The results showed no significant difference in mortality rates between the two groups.
Similarly, when researchers analyzed total water intake — including plain water, beverages and water from food — they found no link between water consumption levels and overall mortality.
Another U.S. study tracking adults for 15 years produced similar results: There was no difference in mortality rates between those who drank more than 3.5 liters per day and those who drank 2.1 liters or less. However, among people with chronic kidney disease, those who drank more than 3.5 liters daily had a 26 percent lower risk of death from any cause compared to those who drank less.
A large-scale study in Australia involving adults aged 49 and older also found no significant difference in overall or cardiovascular mortality between those who consumed more than 3 liters, 2 to 3 liters, or less than 2 liters daily.
One reason you may not need to drink an additional 2 liters of water daily is that a significant portion of our fluid needs are met through food. Many fruits, vegetables, soups and cooked grains naturally contain high water content, and metabolic processes in the body also produce water as nutrients are broken down.
Additionally, the kidneys regulate urine output based on fluid intake, preventing major imbalances. As a result, for most healthy people, drinking large amounts of extra water offers limited benefits.
Thirst is also a natural and reliable indicator. If you feel thirsty, that is usually sufficient reason to drink water, but forcing yourself to drink 2 liters daily is unnecessary for most people.
For those with mildly reduced kidney function, adequate hydration can help, but caution is necessary. In cases of advanced chronic kidney failure or patients on dialysis, drinking too much water can actually harm health rather than improve it.
This article from the Hankook Ilbo, the sister publication of The Korea Times, is translated by a generative AI system and edited by The Korea Times.