8 glasses of water?


In an article published in the American Journal of Lifestyle Medicine, Victoria Vieira Potter, PhD, a professor at Tufts university, challenges the commonly held belief that we should all be consuming 8 glasses of water per day.


Paper citation: Potter, V. Eat your water for health, sport performance, and weight control. Am J Lifestyle Med. 2011, Vol 5, No. 4. pp 316 - 319.


Where did the 8-glass/d advice originate from?

According to the author, in 1945, an individual determined that we should consume 1 ml of water per kcal consumed. Since the average caloric intake was about 1900 kcal, the amount came out to about 64 ounces ( 8 glasses per day).


What are some flaws with this advice?

This idea originated without consideration for the water contained in food and other beverages. This is a major flaw because Americans get approximately 20% of their total water requirements through food. 

Dr Potter also adds:

"Another reason the "8x8 rule" is disregarded is that individual water needs vary remarkably because of differences in physical activity, climate, and a host of other dietary and health factors." 


Are most Americans dehydrated? 

"The new Dietary Guidelines give almost no attention to water requirements, probably because of the aforementioned fact that the vast majority of Americans already achieve adequate hydration."


So what is recommended? 

It is difficult to set a more precise guideline. The author comments: 

"Unfortunately, because hydration needs vary so much among individuals, it would be difficult to establish a more precise dietary reference intake for water." 

However the article does point out the following basic recommendations: 

"Although water consumption per se does not get extensive attention in the Dietary Guidelines 2010, it is recommended that Americans increase their consumption of fruits and vegetables; this inadvertently would increase fluid intake because most fruits and vegetables are about 90% water by weight compared with, for example, meats and refined grains which contain only 40% to 60% water. Because it is estimated that Americans get approximately 20% of their total water requirements through food consumed, increasing the consumption of water-rich foods like fruits, vegetables, and dairy products may have a significant and positive impact on total fluid consumption." 
"Americans should consume water and other calorie-free beverages to help meet their total water needs in place of nutrient-poor, energy-dense beverages such as soft drinks." 




Drinking water throughout the day combined with a calorically adequate, whole-foods, plant-based diet rich in lots of fruits and vegetables,  and the elimination of soft drinks and other non-purely-water beverages, will likely ensure adequate hydration. 

If you are physically active, you will need to take steps extra care to hydrate adequately. Read some basic guidelines on hydration during exercise in this article.

George Cho