Do I really need to drink eight glasses of water a day?

As you grew up until now I bet you must have heard plenty of advice for being healthy; exercising, eating good food or sleeping well etc., But among those suggestions there must be one solid belief stuck in your head. “If you want to be healthy you need to drink 8 glasses (2 liters) of water daily.” This recommendation is widely believed and people look for the scientific evidence. Is reaching eight glasses per day crucial to good health? Is drinking less water affect to physical health? How much water do you really need? You will find the answer quite soon.

To be clear, the definition of ”healthy” in my meaning is the ability to run, swim, talk or do your daily life activities.

But before we go to the experimental part with scientific evidence, I would like to show you some evidence from my daily life.  I have got a friend who is so obsessed in playing sport. So I asked her what if she drinks 8 glasses of water a day or not. Then she said “It’s really hard to happen. My maximum is about 4 or 5 cups.” After I collected the information from people around me, I have got my hypothesis. I think drinking 2 liters of water a day is not a key to be healthy.

I did hold the experiment to disproof this myth by using 3 female volunteers and 3 male volunteers. In the first week, they were allowed to drink only 5 glasses per day. After that, in the last two week, they were ordered to reach 8 glasses a day. During the experiment I would ask about the volunteers’ feeling, their thirstiness and also the ability to do their daily life activities. In addition, I recorded their time in 50 meters running when they drank 5 and 8 glasses of water. Then I collected the data and compared between the 5 glasses intake and the 8 glasses intake conditions.

   

The result shows that there is no significant different outcome between the two conditions but sometimes the volunteers wanted some extra water after the exercise. However, to confirm my experiment I do more research about it by searching for the scientific journal (American Journal of Physiological - Regulatory, Integrative and Comparative Physiology, November 2002, Drink at least eight glasses of water a day. Really? Is there scientific evidence for "8x8"? Valtin H). Therefore, it credible that it is not necessary to reach 8 glasses daily.

By the way, “How much water do you really need?” I can’t give you the specific number because there is no universal requirement for water intake. It depends on your age, gender, body size and others. Furthermore, in the diet like fruits contain a lot of water. So if your diet is full of water-rich fruits, you may not need as much liquid water as you think.

Another suggestion from me is to drink when you get thirsty because it is sign from your body that you are dehydrated. So let your thirst be your guide and adjust your fluid intake depending on your lifestyle and environment. Don’t drink too much or too less water. Drink as much as you want!

Reference:  

American Journal of Physiological - Regulatory, Integrative and Comparative Physiology, November 2002, Drink at least eight glasses of water a day. Really? Is there scientific evidence for "8x8"? Valtin H

Written by Wanarat Chiaowareesajja M.6 No.21 55010022