Hydration: How Much Water Should You Drink?

I have received a few comments about the amount of water that I drink (3-4 L per day), and wanted to quickly touch on the subject of water. We all know that it’s important, but how much water should you drink? And why is it so important? Hopefully this article will answer your questions!

Fast facts about water and the human body

Water makes up 60% of our total bodyweight.

Water is necessary for the transfer of proteins, as well as the transfer of nutrients into cells, and waste products away from cells.

Water lubricates our joints and acts as a shock-absorber for our eyes and spinal cord.

Water is critical in regulating body temperature.

Water is a very important source of minerals (fluoride, calcium, magnesium, etc).

The human body produces roughly 200-300 mL of usable water daily, and even more so in growth stages.

Water loss

We lose water through a few different avenues:

– Through expired air and through evaporation (different than sweating) we lose roughly 650-850 mL daily

– Through sweating (caused by exercise and/or hot climates) we can lose several liters of water. The highest recorded rate ever is 3.7 L per hour. Insane.

– Through feces & urine we excrete, minimally, 400-500 mL per day- normal kidney function requires this basic amount. Again though, this is an absolute minimum, and the amount of water we ingest will increase the amount that we excrete.

What happens when we lose water?

Aside from the things we feel and the things that happen physically when we lose water (headaches, fatigue, thirst, dizziness, flushing, nausea, fainting), here is what happens to your body physiologically:

0.5% loss = Increased strain on the heart

1% loss = Reduced aerobic endurance

3% loss = Reduced muscular endurance

4% loss = Reduced muscle strength, reduced motor skills, heat cramps

5% loss = Heat exhaustion, cramping, fatigue, reduced mental capacity

6% loss = Physical exhaustion, heatstroke, coma

10-20% = DEATH

Most people use thirst as their cue to get a drink, but thirst does not actually even occur until 1-2% of body water is lost. As you see above, even this small loss can cause stress on the body and limit physical performance. This is why thirst is a terribly weak gauge for the amount of water you should drink.

How much water do we need?

There are 2 main ways to determine fluid intake needs. You can either calculate by metabolic rate (for every 100 kcal of metabolic rate, ~100mL of water should be ingested) or by body weight (1L per 50 lbs of body weight). I suggest using the body weight method, as it is easier to do off the top of your head.

Myself, for example: 180lbs /50 = 3.5L ish

This is right on par with most literature, which states that the average person should consume 3 L of water daily. Again though, this is an estimate, and it’s always important to listen to your body. Other important factors to consider include: Body size (the bigger you are, the more water you need), exercise (if you exercise intensely, your daily fluid needs could double), outside temperature (if it’s warmer, you can need up to 500 mL more water regardless of activity level), and diet (high-carb diets help you store more fluids whereas high-protein diets stimulate additional fluid losses due to an increase in urea- a bi-product of protein breakdown).

Long story short, most people will be fine if they consume at least 2 L of water per day, along with coffee/tea and a healthy diet. Extremely active and/or large people will need to increase their water consumption accordingly. I always recommend that my clients aim for 3L+ per day, as more is always better than less.

For athletes and gym-goers

– Make sure you being hydrating before starting an activity/exercise. 500 mL in the 30 minutes before exercise should be the goal.

– During an activity, you should be consuming roughly 250 mL every 15 minutes. Ideally, the beverage can also contain electrolytes (eg, sodium, potassium, chloride, calcium and magnesium).

– Post-exercise you should again consume extra water. The maximum rate of fluid absorption by the body is 1.5 L, so if you become dehydrated, feel free to drink this amount each hour until you feel you are rehydrated.

Conclusion

I currently drink 3-5L of water daily. I exercise intensely 3-4 times per week, and have a high-fat, high-protein diet (increased water loss).  Although I would probably be fine consuming  only 2 L on non-exercise days, I find that my body functions optimally with this increased water consumption- and that’s the name of the game- listening to your body.

As I mentioned in my post about Nutrition on-the-go, I recommend that you all go out and invest in a good water bottle. My Nalgene and I are inseparable. I’m looking at mine right now. I am not thirsty, but I am drinking water.

If you have any additional questions about why you need water, or about how much water you should personally be consuming, don’t hesitate to contact me!

Happy hydrating!

– DW