"But caffeine is a diuretic, so not only does it make you want to go to the bathroom more, it also makes you more dehydrated."
The University of Conneticut Sports Medicine Department did a study that seems to indicate that coffee is as much a diuretic as is water. Do you have data from some study that indicates otherwise, or are you repeating an old wives tale?
I have asked several docs and looked for the data. The 8/8 or 64 oz. of fluid per day is an urban myth. (It used to be that it was 6 glasses per day, but I guess there has been inflation.) Please provide the data to confirm the need for 64 oz of fluid per day.
I have found that sipping small amounts of water through a flight helps rehydrate without requiring the need for relief. The trick is to begin a flight hydrated and replace water gradually as you lose it. Small amounts should keep you from having to make a pit stop every 30 minutes.
Days, and I mean DAYS at altitude may result in unpleasant symptoms if you don't properly hydrate to compensate for the dryer air especially during excersise. The cooler temps at altitude contribute to the lack of urge to drink too.
Sitting on your tail in any machine, even in the dryest conditions, is just not going to tax your hydration level! Surely (hopefuly!) you won't be hyperventilating through a four hour flight but even if you were, it will be tough to lose so much water that you get dehydrated. This is a non issue if you start your flight in a reasonably healthy state. Ask an athlete about hydration. And yes, Charlie M's got it right on the caffeine myth.
Certainly different people have different daily water requirements and widely varying amounts of dehydration tolerance. The 64 ounce per day is most likely an average across an entire population; most smaller people will probably need lesswater and larger folks will probably require more fluids. I certainly have felt coffee's diuretic effect.
Here is an opinion from http://www.buzzle.com/articles/is-coffee-a-diuretic.html:
"Is Coffee a Diuretic or Not?
Caffeine has been considered to be a diuretic by experts and consumers for years now. Some people believe that drinking caffeinated beverages will make them lose fluids so they can't be counted as part of their daily intake. Others say that caffeinated beverages do not lead to increased fluid losses. To get a clear final picture of these contradictory statements is by seeing the results of research studies.
Water is lost from our body through respiration from lungs, skin, renal, and gastrointestinal tract. Many factors such as age, activity level, health, diet, and environment can affect the water balance in our bodies. Some research has shown that caffeine intake can also be an important factor that can affect our fluid balance. In one study, 12 regular caffeine consumers were told to abstain from caffeine for five days at a stretch and they were then given 642 mg of caffeine in the form of coffee. The urine output of these individuals increased when the caffeine was given. Another separate study done on eight men tested the effect of 45, 90, 180, or 360 mg of caffeine on urine volume output, so as to see its effect as a diuretic. Coffee containing caffeine at 360 mg dose led to a substantial increase in the urine output. One limitation to these studies is that they did not evaluate the impact of caffeine when it was consumed on a regular basis. A onetime dose may affect the body differently when compared to daily consumption. Read more on is coffee bad for you.
Initially it was said that caffeine had no significant impact on final urine output. Subsequent studies have also shown that diuretic effects of caffeine are dubious in nature, as caffeine containing beverages did not impact urinary output any differently when compared to other beverages. However, this does not mean that caffeine does not increase your need to urinate, as it is a mild diuretic. Coffee consumption levels is what will dictate your reaction and your tolerance level. Thus, the eventual effect of caffeine and coffee will vary person to person and you will need to monitor your reaction and tolerance to caffeine to determine how you are affected by it. Water was, is and always will be the recommended choice for optimal hydration, so be sure to include it as part of your daily fluid consumption. Read more on is caffeine bad for you.
This was all about answering the question 'Is coffee a diuretic?' The fact is that coffee and almost any beverage in fact, does lead to mild effects as a diuretic. Coffee consumers however, have a higher tolerance to the mild diuretic effect of coffee. On the contrary, coffee is said to be a powerful stimulant of the bowel, which in turn is responsible for preventing constipation. However, excess of coffee can also lead to very loose bowel movements. "
To me it is interesting that many people, after toiling all day at work, can't hit their favorite watering hole soon enough. Why do the do that? Sure, it's because they like a drink or two after work or perhaps want to drown their sorrows. But certainly many of them are at least somewhat dehydrated after a long day with little or no fluids and that is their way of rehydrating and having fun at the same time. And there's no doubt about alcohol's diuretic effect.
My airplane has a "relief tube" strategically placed near the pilot's seat, so I have no qualms about getting fully hydrated before takeoff. Kind of awkward though, with friend in the airplane. But if you gotta go... I'll bet aircraft renters get more deydrated than owners on long trips, just because rental planes typically lack relief tubes. Yet another good reason to buy an airplane.
Wanna reduce your caffeine intake to reduce dehydration? Consider drinking Decaf, which has about half the caffeine as regular coffee.
Surrey, British Columbia