Why does exercise decrease the diuretic effect of caffeine?

[thunderfvck]

WHat reactions consume so much water in the digestion of ethanol?

 

[Chemicalsuperfreak]

Originally posted by thunderfvck
WHat reactions consume so much water in the digestion of ethanol?

Alcohol is a diuretic. It makes you piss all your water away.

 

[adrenaline]

alcohol causes diuresis presumably resulting from inhibition of vasopressin (also called antidiuretic hormone) release from the posterior pituitary gland

 

[Monique]

Is caffeine a diuretic too?

 

[adrenaline]

Yes..due to direct stimulation of the secreting apparatus in the kidney, as well as by generally raising the arterial tension in the renal tubules. For some reason this action is more apparent at rest than during excercise.

 

[Monique]

Originally posted by Monique
Is caffeine a diuretic too?

It's seems that the scientific community says it isn't, so maybe something is wrong with me, 'cause my experience is that coffee and coke both make me have to use the bathroom

 

[Monique]

Originally posted by adrenaline
Yes..due to direct stimulation of the secreting apparatus in the kidney, as well as by generally raising the arterial tension in the renal tubules. For some reason this action is more apparent at rest than during excercise.

It IS? That makes me feel better but it doesn't interact with vasopressin?

 

[adrenaline]

From the medical community standpoint, caffeine is no more a diuretic than water during normal excercise status (studies by a excercise physiology guru Armstrong) demonstrated no more dehydration in those athletes who preceded their workouts with caffeine. However, most people have taken his data and extrapolated to caffeine is not a diuretic. At rest, or in couch potatoes it is. Also, with chronic usage you become less sensitive to the diuretic effects.

 

[Monique]

lol, so that is scientific proof I'm a couch potatoe anyone else? but no, apparently the exercise overrides the diuretic action of caffeine, maybe it gets metabolized faster?

 

[adrenaline]

Not sure about the mechanism of action there. Will need to look into it.

 

[adrenaline]

Originally posted by Monique
lol, so that is scientific proof I'm a couch potatoe anyone else? but no, apparently the exercise overrides the diuretic action of caffeine, maybe it gets metabolized faster?

I could not find any specifics but I will extrapolate based on basic excercise physiology. Remeber, caffeine in sedentary state increases urine output by increaseing the GFR or glomerular filtration rate by increasing the afferent blood flow to the renal tubules and also somehow works on the distal tubules in terms of sodium reuptake regulatory mechanism. At rest, 15-20% of blood goes to skeletal muscle; during exercise, this amount increases to 80-85%. Thus blood flow to visceral tissues and inactive skeletal muscle reduces and kidneys reduce. We also start releasing antidiuretic hormone which probably overrides the caffein's effect on the distal tubule in terms of sodium reuptake and the general shunting of blood decreases the glomerular filtration rate. I have yet to find actual studies to confirm this but that is my basic assumption.