The Hydration Debate Gets Heated

The Hydration Debate Gets Heated | The Paleo Diet
As we move into the summer, the competitive season for endurance sports hits full swing. Regardless if you’re an experienced runner or novice, you’ve likely been reminded by your run coach or peers “make sure you drink enough water during your run!”

For years the recommendation from run coaches has been to drink before you are thirsty, to prevent dehydration and subsequent decrements in performance. But if you aren’t racing at the front of the pack, do you need this much water?

Hydration is currently a hot topic and it’s divided into two main camps: the traditional camp who believes you should pre-hydrate by drinking 8 cups of water daily, versus a growing camp who believes you should only drink when thirsty. It can be a complicated topic, especially when the men and women in white lab coats can’t even agree on the best strategy. So, what are the best guidelines for you?


The American College of Sports Medicine’s (ACSM) recommendation for endurance athletes is to consume 5-7ml water per kilogram bodyweight in the four hours before exercise. This translates to approximately 340-477ml for a 150 lb. female and 455-636ml for a 200 lb. male. The general recommendation is to drink until your urine is clear. This seems very reasonable, so why the sudden change in thinking?

Unfortunately, it’s not quite that straightforward. Just because you drink water doesn’t mean you’re absorbing the water. The composition of the water largely determines how much you absorb. If you drink distilled water with no salt, you won’t absorb the water and you’ll begin to deplete your blood sodium levels leading to hyponatremia.


 Hyponatremia sets in when the fluids you consume are greater than the amount of fluids you lose via sweat. Common symptoms of hyponatremia include nausea, muscle weakness, and disorientation, which can be easily confused with symptoms of dehydration. The problem becomes dangerous if you give a person suffering from hypoatremia more water. Increased water will further dilute their blood sodium levels which can lead to cerebral edema, pulmonary edema, and death.

When a Boston marathoner died of hyponatremia in 2002 the wheels were put into motion to find the answers behind what hydration strategy is safest for all athletes. This led to the recent “drink to thirst” stance on hydration and a new set of recommendations.


In fact, this new thinking goes all the way back to the early 1990s when a ground-breaking study was published by Dr. Tim Noakes PhD and his colleagues regarding the potential danger of overconsuming water during exercise. Contrary to popular belief, they found drinking too much water was far more dangerous than not drinking enough. The body’s inherent mechanism to maintain hydration balance has since been shown to be more than enough to keep you hydrated and prevent the catastrophic effects of hyponatremia. This has led to changes in recent recommendations for endurance athletes to simply “drink to thirst.”


The composition of your water – specifically the amount of salt and carbohydrates – plays a major role in hydration and your capacity to actually absorb the water you are drinking. Just because you drink a lot of water, doesn’t mean you’re hydrated. If you pee just as much as you drink, you’re likely not making the most of your water intake. Many people can actually drink less and be more hydrated.

As mentioned above, if you drink too much distilled water you’ll flush out sodium from your body, depleting blood sodium levels and leading to hyponatremia. Fear not, it’s very rare to die of hyponatremia, but if you’re an elite level athlete it’s still a major concern.

You need salt and carbohydrates added to your water to maximize absorption. Nature is very smart; the fructose in a piece of fruit is naturally surrounded in fibrous pectins, which lead to a gradual release of fructose for energy. In sports drinks, your gut receives a large bolus of fructose all at once which can slow gastric emptying rate or the speed at which food and liquids leave your stomach. Too much fructose, or too many sips from a sports drink can lead to bloating, discomfort, and subsequently poor performance.


Interestingly, there are differences between men and women when it comes to hydration. The female hormonal terrain is more complex than that of men, which impacts the hydration question. The research of Dr. Stacey Sims PhD highlights that women are more susceptible to hyponatremia during their high hormonal phase – between ovulation and menses – than during their low hormonal phase. Furthermore, fructose is poorly absorbed in women compared to men, which can slow gastric emptying rate.

So, what does this mean for you if you are a woman? Effectively, a “drink to thirst” strategy is not the best approach as hormonal shifts in estrogens as well as high stress (e.g. exercise!) can alter vasopressin release, which decreases a woman’s thirst cue during the high hormonal phase.


Your hydration plan should depend not only on your gender, but your level of competition and general state of hydration. To stay hydrated away from competition, a Paleo diet is a great platform for maintaining hydration because it’s naturally high in vegetables and fruits, which provide a wealth of water and electrolytes to help keep you hydrated.

A general way to tell if you’re adequately hydrated is to look at the color of your urine. If it’s completely clear, you are likely over-consuming water and over-hydrating. If your urine is a darker yellow color, you likely need to increase you veggies and fruit consumption and add more water into your diet (Note – if you are taking a b-vitamin supplement it will lead to a very bright yellow urine. This does not mean you’re dehydrated). A urinalysis test can confirm your hydration status.

The average exerciser likely does not sweat enough to warrant the ingestion of large amounts of water and the old refrain of having a cup of water at every drink station isn’t necessarily the best strategy. Don’t worry about passing over a few water stations at your next race, let thirst be your guide and simply drink if you feel thirsty.

For elite runners, a useful strategy to determine your hydration plan is to weigh yourself before and after your run. If you’ve gained weight then you’re definitely over-consuming and you need to dial back your water intake.  If you lose more than 2% of your bodyweight, you need to bump up your intake.

It’s great to see so many people being active and training to compete in 10k, half and full marathon events throughout the summer months. Listen to your body and pay attention to a few key metrics – bodyweight, urine color, hormonal phase in females –  to ensure you’re optimally hydrated to look, feel, and perform your best!

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“5” Comments

  1. Hydrating our bodies is indeed very important. But the type of water with which we’re hydrating is also important. Distilled water is good for detoxing and such. But relying on it solely can also be detrimental for one’s health as it is completely stripped of minerals that our bodies need. It is also high in acidity. We should be more conscious when it comes to water because despite what most of us think, water isn’t just water.

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  4. Finally, something I can read on hydration that’s filtered for the public that I agree thoroughly on!! Very well written, with excellent points addressed and presented!! Very well done!

    • Doctors Brown and Bubbs,
      What is the consensus on using salt substitute AKA Potassium Chloride. And what would the general optimal intake as a percentage of sodium Chloride be? Especially if you are hypertensive…

      • Hi Allan,

        When we look at sodium intake, it’s actually the ratio of sodium to potassium that is critical. Rather than simply lowering sodium, you need to increase (sometimes dramatically) potassium intake. The best way to do this is to eat more veggies. Personally, I would prefer this to using salt substitutes.

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