You don't need '2 liters of water a day' for your health and diet, what is the amount of water you really need?
Many people have heard from magazines and internet information that '2 liters of water a day' is necessary for health and diet. However, Tamara Hugh-Butler, an associate professor of exercise and sports science at Wayne State University, points out the problem, saying that the idea that 'everyone should drink 2 liters a day' is misleading.
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◆ Misunderstanding of '2 liters of water a day'
According to Hugh Butler, the scientific basis for the idea that 'a person needs 2 liters of water a day' is not clear. In the 2018 study, this advice is derived from the Dietary Reference Intakes of the US Food and Nutrition Board, which was announced in 1945, and not due to primary research has been written . The European Food Safety Authority announced a similar claim in 2019, but the water here is not the water alone, but the total amount of 'water contained in all drinks and foods'. In other words, 2 liters includes the water content of fruits and juices, and the phrase 'you need 2 liters of water a day' is misleading, Hugh-Butler pointed out.
Alcohol certainly has a diuretic effect, but Hugh-Butler cautions that caffeine in coffee and tea does not excrete urine in excess of the water content in drinks. I did.
According to Hugh Butler, the amount of water a person needs is mainly determined by the following three factors.
・ Weight: The larger the body, the more water is needed.
-Environmental temperature: The higher the temperature, the more people sweat and lose water, so they need water.
-Exercise level: The higher the intensity of exercise, the more water is lost, so water is needed.
For this reason, the amount of water required for everyone is different, and it is inappropriate to set a uniform standard, Hugh-Butler said.
◆ Why is water important?
Hugh-Butler explains that the reason why the importance of 'drinking water' is so emphasized in the first place is that the overall water balance of the human body is so complicated. ..
Mammals regulate water balance in real time with their kidneys. It is said that the kidney has a water channel of 'aquaporin 2 (AQP-2)' that responds to the
The adjustment work by the cooperation of the brain, cranial nerves, and kidneys is very quick, efficient, and accurate.
◆ Results of scientific research on 'drinking water'
There are several scientific studies on drinking 2 liters of water a day. For example, drinking 2 liters of water a day has been shown to reduce stones and reduce urinary tract infections in people with a history of kidney stones. On the other hand, there is no scientifically clear evidence of the effects on renal function, improvement of constipation, or changes in facial skin color. A study of children also showed that drinking more water does not help with weight loss unless the intake of high-calorie juice is reduced or the feeling of fullness is not felt before meals. I will.
On the other hand, drinking water has also been shown to affect the mental state of some people. Subjects reported an improvement in cognitive ability after increasing the water intake study and, reports on women's anxiety to improve the mood by water intake also exist . In the latter case, women are obsessive about drinking water, and it is believed that water intake activates the reward circuit.
However, unnecessary fluid intake makes the brain feel uncomfortable, and the muscles also need extra movement. Social polydipsia causes polyuria and causes bladder dilation, ureteral dilatation, renal failure, and hydronephrosis, which is thought to cause brain discomfort.
In conclusion, Hugh-Butler said, 'Unless you're thirsty, drinking extra water probably doesn't have any significant health benefits, but it doesn't hurt.'
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