News to me that mate doesn't have caffeine!
From Wikipedia: "Mate contains xanthines, which are alkaloids in the same family as caffeine, theophylline, and theobromine, well-known stimulants also found in coffee and chocolate.
Caffeine content varies between 0.3% and 1.7% by dry weight, when compared to 2.5–4.5% for tea leaves, and 1.5% for ground coffee."
http://www.econsultant.com/articles/caf ... offee.html
A 10g aliquot does not a serving make (unless you are purchasing it from clever vendors that both dilute it with flavorings and peddle it in a teabag to maximize profit), so the caffeine content is greater than tea and on par or greater than coffee - but, it has a nice dose of antioxidants to go along with the metabolic stimulants, to offset the negative effects.
So if you prepare it in the traditional way - packed in a gourd, you are getting a LOT of stimulant.
One of the more interesting aspects of these alkaloid stimulants is that they encourage release of dopamine. As you may recall from my previous posts, low dopamine is associated with depression.
A 2005 patent claims that Yerbe Mate is a monoamine oxidase inhibitor (MAOi), a class of anti-depressants. It appears to interfere with MAOi-type drugs, so one might want to be careful if you are taking this form of antidepressant.
For the curious reader, the rationale is this:
Your body synthesizes the related monoamine neurotransmitters serotonin, dopamine and epinephrine, in a pathway, such that the most excitatory, epinephrine is produced and stored under very controlled conditions.
You don't want to be pumping out epinephrine (adrenaline) constantly. Thats the 'fight or flight' hormone behind various nervous disorders.
So MAOi drugs reduce the potential for making and storing epinephrine and therefore act in a backward control loop to help reduce hypersensitivity to it by oversecretion.
Wikipedia authors obviously don't know their biochemistry. Oh well. They comment on the antianxiety effect of yerba mate consumption without understanding why.
The magnesium and potassium ion content of yerba mate counter the stimulant effect, that is, to induce release of calcium ions (a second messenger ion that acts like a hormone within central nervous and secretory systems). So you get a definite buzz, but a relaxed type, not the anxiety, jaw-clenching, heart palpitation, and intestinal motility effects of caffeine in susceptible folks.
Bolus doses of caffeine induce insulin release in the pancreas. Yet another reason to avoid caffeine if you are a smoker, are overweight or are a slug (sedentary).