I have heard it since I was a kid: Drink plenty of fluids means water. It doesn’t include caffeinated beverages like tea. That statement didn’t come with much explanation when I was little. Later, Mom explained that only clear liquids count. I couldn’t figure out why 7-Up was okay when I was sick, but iced tea wasn’t. When I got married, my wife explained to me that it was the caffeine that caused the problem. Caffeine, you see, is a diuretic. That means it makes you pee. The more you drink, the less hydrated you are. This explanation has always bothered me, but I never went to the trouble to research it for myself.

Until now.

I came across a paper entitled Caffeine ingestion and fluid balance: a review, by R.J. Maughan and J. Griffin. They reached the conclusion that large amounts of caffeine consumed by people unused to caffeine can, indeed, cause dehydration. On the other hand, people who regularly drink caffeine can consume quite a bit of it without a problem. To quote their results directly:

“The available literature suggests that acute ingestion of caffeine in large doses (at least 250-300 mg, equivalent to the amount found in 2-3 cups of coffee or 5-8 cups of tea) results in a short-term stimulation of urine output in individuals who have been deprived of caffeine for a period of days or weeks. A profound tolerance to the diuretic and other effects of caffeine develops, however, and the actions are much diminished in individuals who regularly consume tea or coffee. Doses of caffeine equivalent to the amount normally found in standard servings of tea, coffee and carbonated soft drinks appear to have no diuretic action.”

In conclusion, when I am sick and/or dehydrated, I may feel free to drink my tea.

But wait! It gets better! I came across another paper entitled The effect of drinking tea at high altitude on hydration status and mood by D. Scott, J.A. Rycroft, J. Aspen, C. Chapman, and B. Brown. This is an absolutely awesome study, simply because they performed it at Mt. Everest base camp. It’s not a statistically valid sampling (only 13 people participated), and I’m not sure how valid a study performed at 17,500 feet altitude is for us lowlanders at 5,500 feet. But, hey, it was done at Mt. Everest base camp, and the procedure they used in the study does seem reasonably rigorous.

To put the results in their own words:

“The study shows therefore that even when drunk at high altitude where fluid balance is stressed, there is no evidence that tea acts as a diuretic when consumed through natural routes of ingestion by regular tea drinkers, but that it does have a positive effect on mood.”

Immediately upon reading this, I began putting together a list of people that might benefit from a few cups of tea. There are even those rare occasions when my own mood is not particularly sunny and bright. Not many, of course, but I must be prepared and have some good tea set aside for those moments.

Alas, upon closer reading I discovered that the “positive effect on mood” is actually “subjects reporting reduced fatigue when tea was included in the diet.” Oh, well. If you think about it, tea has long been touted as a good relaxant, so this particular finding makes sense.

With my hopes for a worldwide cure for bad moods rudely dashed, I shall have to fall back on tea as a way to hydrate and reduce fatigue. Sounds like the perfect thing to have along on a hike or at the gym. Surely that’s no surprise to my tea-loving readers!