I was told that tea is a diuretic so was wondering, if given to a person who is very thirsty / mildly dehydrated does it do more harm than good? Surely because of the water content, it would help rehydrate the body, however, because of the diuretic effect, could it make matters worse? (This is purely a hypothetical question, to say if a cup of tea was the only drink available to hand).
I'm asking for a medical / scientific point of view, please.
FWIW this was disccussed on QI and the rehydration effect of tea, coffee, milk, beer etc far, far, far exceeds any negative diuretic effect. The only no no mentioned was sea water.
The diuretic effect of tea occurs after the water has been absorbed by the body so that you need to drink more later to replace the water lost owing to the diuretic effect of the tea. If you drink more tea to replace the lost water you can get into a vicious circle of peeing and drinking tea, spending your day feeling thirsty and peeing all the time. The way to get out of this is to drink fruit juice or water between cups of tea. This may sound sacriligious to a Brit but 3 cups of tea a day is probably enough. I cut down to 2 cups of tea or coffee per day many years ago and feel a lot better for it.