I'm weighing in on Joe Forte's side here. Coffee dilates, not constricts, capillaries

As a long-time coffee drinker, I fairly regularly switch out my regular brew for the decaf version of the same (Trader Joe's House Blend, if you're wondering) when I'm going on some kind of excursion.

Don't badmouth coffee, motherfucker!

If this thread is about coffee, give me tea. If this thread is about tea, give me coffee.

Hell just give me something with caffine. Sometimes I like to follow up my Coffee with Coke (the drink not the drug) or even a Red Bull.

Nope.

Caffeine has an antagonistic effect on Adenosine A2a receptors. Stimulation of those receptors causes vasodilation. Thus, the antagonistic effect is vasoconstriction.

While one could argue that caffeine does not vasoconstrict DIRECTLY, it would be wrong to say it vasodilates.

Thanks for the additional proof that it is a vasodilator. It INCREASES blood flow to the extremities.

I did a quick google search for "caffeine vasodilator" and came up with tons of hits that said it is a smooth muscle relaxer and an overall vasodilator.

Don't badmouth coffee, motherfucker!

www.rxlist.comcgi/generic/ergot_ad.htm

www.emedicine.com/emerg/TOPIC949.HTM

The first is written by a clinical pharmacologist. The second by an emergency physician.

It does dilate the bronchioles, that is true. But it constricts the blood vessels.

Your first citation is mostly about ergot suppositories.

The second contains this quote "acts as an adenosine antagonist, resulting in peripheral vasodilatation and CNS stimulation. Caffeine is a potent releaser of catecholamines (norepinephrine and, to a lesser extent, epinephrine) that increases cardiac chronotropic and inotropic activity, bronchodilation, and peripheral vasodilatation."

The diuretic effect of coffee is so mild that it does not cause dehydration.

Some investigators have hypothesized that caffeine is a vasoconstrictive substance.3, 4, 5, 6, 7, 8 and 9 In the present study, systolic and diastolic blood pressures were elevated after caffeine ingestion, suggesting vasoconstrictive effects of caffeine.5 Caffeine should be an antagonist of the adenosine receptor.10 and 11 It is well known that adenosine induces vasodilation. Therefore, antagonization of the adenosine receptor could induce vasoconstriction. However, although oral caffeine ingestion did not change baseline FBF, FBF response to ACh was significantly increased in the caffeine group. Hatano et al12 reported that caffeine promotes nitric oxide synthesis in the endothelium by the release of Ca2+ from the endoplasmic reticulum through activation of the ryanodine-sensitive Ca2+ channel and the suppression of cyclic guanosine monophosphate degradation in the isolated rat aorta, resulting in the caffeine-induced augmentation of endothelium-dependent vasodilatation. In the present study, l-NMMA, a nitric oxide synthase inhibitor, completely abolished the caffeine-induced augmentation of endothelium-dependent vasodilation. These findings suggest that caffeine augments endogenous nitric oxide production by agonist stimulation. A balance of the vasodilatory effect of caffeine as an endothelium-dependent vasodilator and the vasoconstrictive effect of caffeine as an adenosine receptor antagonist may regulate vascular function.

While caffeine may influence your performance on any given day, you are more likely to experience greater benefits from adequate rest, proper diet and hydration than from the use (or lack of) of caffeine.

That does not speak to your attitude when your feet hit the floor in the morning or potential withdrawl if you suddenly stop drinking that morning espresso!

Nope.

Caffeine has an antagonistic effect on Adenosine A2a receptors. Stimulation of those receptors causes vasodilation. Thus, the antagonistic effect is vasoconstriction.

While one could argue that caffeine does not vasoconstrict DIRECTLY, it would be wrong to say it vasodilates.

I guess what I'm saying is that you are most likely correct, but it is not as simple as saying that it antagonizes this receptor, therefore it must have this effect. There are many other factor that determne the physiologic effect.

i think this thread has gone too far. it's coffee! drink it up!