It’s summer and it’s hot.  Seems like the ideal time to write about hydration.  First, I’ll comment New York Times Health Section features the piece titled In Summer’s Heat, Watch What You Drink.  The article has two main points.  The first point concerns our fluid intake and the idea that we likely aren’t drinking enough to replace water lost to perspiration.  The second point deals with high-calorie drinks and the fact that it’s easy to consume too many calories in our quest to hydrate ourselves.  This post regards the first point.

Regarding fluid intake, the article suggests that a) our thirst is a poor guide for fluid intake and b) a quenched thirst is equally unreliable as a guide.  The suggestion is that we should multiply our weight in pounds by 0.08 and then drink that number’s worth of eight-ounce cups of water daily.  Sounds a little complicated to me.  Prior to the advent of mathematics, how did early homo sapiens drink enough to survive?

(The above mentioned formula is almost as complicated as this one.  If you’d like to further complicate your drinking habits, try the test described here.)

In the recent past, we were advised to drink eight glasses of water a day.  No one is entirely sure where this advice came from.  Then we were given formulas like the above mentioned methods to figure out how much fluid we needed to consume.  There was and still is widespread fear that a little dehydration would certainly cause cramps, delirium, and possibly death.  Like the Times article, much of the popular advice told us our thirst wasn’t a good guide–that to wait until we were thirsty to drink was to wait too late.

In recent years though we’ve seen new hydration guidelines.  These guidelines are much simpler, more instinctive and easier to follow.

A list of the old vs. new rules of hydration can be found on Active.com.  The best new rule in my view is to drink according to your thirst.  Excellent.  That’s what thirst is for right?  A signal that it’s time to drink.  The article states,

“The idea that thirst comes too late is a marketing ploy of the sports-drink industry,” says Tim Noakes, M.D., a professor of sport and exercise science at the University of Cape Town, South Africa. While thirst is not a perfect indicator of hydration status, it does appear to be a good indicator of the optimal drinking rate during exercise, according to Noakes. “The answer is just drink as your thirst dictates.”

Another new rule is to drink to slow dehydration rather than drink to completely prevent dehydration.  Studies show that the effort to drink to completely prevent dehydration is nearly impossible and uncomfortable.  Slight dehydration is not a health threat despite many popular fear to the contrary.   To that point, overhydration or hyponatrimia is far more dangerous.

(One easy hydration check you can use regards urine color, as advocated at Ask the Dietitian.  Dark urine means you need more water.  Light yellow means your adequately hydrated.)

Next, sports drinks are superior to plain water if your activity lasts more than one hour.  Sports drinks contain important electrolytes such as sodium, calcium, magnesium, potassium, and phosphate as well as carbohydrates for fuel.

Some sports drinks such as Accelerade and Hammer’s Perpetuem contain protein.  At least one study suggests that consuming small amounts of protein during a workout boosts performance.  Be careful though.  Some people (like my wife) experience gastrointestinal turmoil when they consume such drinks.

Next new rule regards caffeine.  Previously, we were told that caffeinated drinks would dehydrate us.  Now we’re told that isn’t quite the case.  Caffeine can be a powerful ergogenic aid that may aid performance but it doesn’t seem to be inhibit adequate hydration.  (Alcohol on the other hand definitely promotes dehydration.)

Finally, cold fluid is best to drink when it’s hot.  (Similar to thirst, this seems instinctively obvious right?)  It was once suggested that warmer water emptied out of the stomach faster but that’s no longer regarded as true.  Nor does cold water promote cramping.

In conclusion, don’t complicate things.  Drink as much (cold) fluid as you feel is appropriate.  Drink a sports drink if you’re out in the heat for over an hour.  You may want to experiment with protein and/or caffeine.