How much do you really need to drink?

Posted on Tuesday, September 15th, 2015

Written by Lindzie O'Reilly

 Many of us grew up being told that drinking water is important and that we should aim for eight cups each day. Recently, this recommendation has been called into question. It’s true that there really is no research to suggest that each and every one of us NEEDS to guzzle eight cups of water per day.

We are all different. Many factors will affect your water needs including your activity level, your body shape and size, and the temperature outside. We also get water from many sources – eating more fresh foods such as fruits and veggies will result in more water from food compared with eating drier foods like granola bars, meat or bread.

According to Dr. Stanley Goldfarb, a University of Pennsylvania kidney specialist, thirst serves as an accurate indicator of water needs. He advises to drink when you feel thirsty and cautions that drinking when you are not thirsty will not have any extra health benefits. 

Dr. Stephen Cheung, an elite cyclist and researcher at Brock University recently conducted a study examining the effect of hydration status on cycling performance. Contrary to the common message we receive about the importance of hydration for exercise performance, Dr. Cheung concluded dehydration has NO effect on cycling performance! It is important to note that his study included only eleven individuals, all of whom were elite cyclists, so this result may not necessarily apply to the average individual. Even still, I found this result very surprising given the amount of information we are bombarded with related to the importance of hydration when exercising.

So…drink when you’re thirsty, don’t if you’re not. Case closed, right?

Wrong! I’m afraid it may not be quite that simple. Just like with hunger, we each perceive thirst in a different way. For some, thirst may come in the form of a headache or trouble concentrating rather than a parched throat or lips. Additionally, when we are busy or stressed, we may not always notice thirst cues, meaning that we go through the day dehydrated and only realize how thirsty we are when we arrive home at the end of the day. Students with a high stress and fast paced schedule are particularly susceptible to this.

A recent study of healthy college aged women by Munoz et al. (2015) revealed a pretty strong correlation between water intake and mood. The researchers concluded that individuals with a higher water intake experienced lower tension, depression, confusion, and total mood disturbance compared with individuals with a lower daily water intake. They also noted that individuals with high versus low water intake did not feel any more thirsty, suggesting that the individual’s perception of thirst might not be a great indicator of fluid needs.

So…now what?

I do believe that we are all different and that we do not need to go by the old ‘eight cups per day’ rule. Some of us will need more and some of us will need less.

I also do not believe, however, that we can rely solely on thirst, as stress or a busy schedule could potentially mask thirst cues.

Instead, try carrying a water bottle with you so that you always have water available. Take it out of your bag and place it on the desk in front of you when in class or in the library to remind you to drink. Sip water with meals. Give yourself lots of opportunities to drink and let your thirst dictate the amount you sip each time you drink.

Choose water as your main fluid. Limit intake of caffeinated beverages to no more than 4 cups (2 Tim Horton’s mediums) per day. Choose high sugar options such as pop, iced tea and juice less often.

Questions or thoughts? Email me at 

Interested in booking a FREE one-to-one nutrition appointment to talk about your food habits? Call x52131

News Archive