If only the answer were that straightforward! The amount of water our body needs to thrive varies considerably depending upon who you ask, and a long list of variables. Eight glasses per day might be what you've been told, or have always believed . . . but is it correct?
Disclosure: This post may contain affiliate links, which means that as an Amazon Associate I earn from qualifying purchases. Learn more here.
It might be. For some people. But it’s not that simple.
The recommendation to drink 8 glasses of water per day comes from ancient “research” that hypothesized that because humans lose around 2.5 litres of water per day, they should also consume that much.
But what does Dr. Google say? As expected, you get a pretty wide range of answers, few of which appear to be evidence-based. But even the evidence-based answers vary considerably.
In my google search, these are the answers I found.
The standard 8 cups per day
8 to 10 cups per day
4 to 6 cups per day
2/3 of your weight (pounds) in ounces (for me this would be roughly 10.5 cups)
1 millilitre per calorie you consume (this averages to around 9 cups for women and 11 for men)
Your weight in pounds times 2/3, plus 12 ounces for every 30 minutes of exercise (for me this equates to 12-13 cups per day)
Your weight in pounds divided by 2.2, times an age dependant multiplier (under thirty: 40, thirty to fifty-five: 35, fifty-five+: 30), divided by 28.3, plus another 5+ cups for every 45-60 minutes of physical activity you do (using this calculation my water intake should be roughly 14 cups per day)
Based upon research collected and scrutinized by Dr. Greger of nutritionfacts.org (2015), the best evidence suggests that women should consume 4-7 cups per day while men should consume 6-11 cups per day when exercising moderately in average climates. This is in addition to up to 1 litre of water typically consumed through food and made by our body, and does not include caffeinated, sugary or alcoholic beverages, whereas some other recommendations do (although most do not specify). If your diet is lacking in the fruit and vegetable department your needs will be higher, unless of course you start eating more fruit and vegetables.
One Size Does Not Fit All!
So even the best research has a huge range. This is for good reason. There are so many variables that come into play, you simply cannot recommend one specific amount for everyone. Our hydration needs vary considerably based upon factors such as age, weight, sex, physical activity level, climate/temperature, humidity, medications, health status, diet (are you eating fruit/vegetables high in water or more processed foods high in sodium?), and if you are pregnant or breastfeeding. Your needs one day also may not be the same the next. Our bodies are pretty good at adapting and letting us know when we need to hydrate, however it is also important to consciously keep on top of it to avoid getting dehydrated.
Some indicators you might not be consuming enough water include the following:
Dark yellow urine (it should be light yellow)
Strong smelling urine
Frequent headaches (dehydration causes a reduction in blood volume which results in less blood to the brain)
By contrast, proper hydration (with water) has been associated with the following benefits:
Helps with weight loss/maintenance
Regulates body temperature (through sweating)
Helps facilitate the removal of waste products via the kidneys
Helps maintain a healthy blood pressure
Aids in proper digestion
Helps improve skin health
Helps clean the mouth and prevent tooth decay
Increases blood flow to the brain and improves concentration and memory
Helps prevent muscle cramping during exercise
Helps prevent constipation
Helps reduce the chance or severity of a hangover
Can you drink too much water?
Although not impossible, for a majority of the population it would be extremely difficult to drink enough water for it to be harmful. A few people do need to be careful though. Too much water can be harmful for those who have heart, liver or kidney problems, thyroid disease or are taking medication that can cause water retention, such as NSAIDs, opioids and certain antidepressants. If this describes you, check with your doctor to determine how much water you should be consuming per day.
So . . . how much water should YOU drink per day?
The short answer is, probably more than you currently do. Determine what your current baseline is and experiment with it to find an optimal amount that realistic. Set a benchmark for how much you want to consume (if your current water intake is quite low, make it gradual) and consistently track your consumption. Find the sweet spot to not just ward off dehydration, but to maximize the many health benefits of staying properly hydrated. Make water your drink of choice, and do it consistently to make it habit (learn more about building habits/routines here). Stay tuned for a post on tips and tricks to drink more water!
For help setting a goal, be sure to check out my free goal setting guide.