4.7. Caffeine and your metabolism.
Description
This article is from the Coffee and Caffeine FAQ, by Alex Lopez-Ortiz with numerous contributions by others.
4.7. Caffeine and your metabolism.
Caffeine increases the level of circulating fatty acids. This has been
shown to increase the oxidation of these fuels, hence enhancing fat
oxidation. Caffeine has been used for years by runners and endurance
people to enhance fatty acid metabolism. It's particularly effective
in those who are not habitual users.
Caffeine is not an appetite suppressant. It does affect metabolism,
though it is a good question whether its use truly makes any
difference during a diet. The questionable rationale for its original
inclusion in diet pills was to make a poor man's amphetamine-like
preparation from the non-stimulant sympathomimetic phenylpropanolamine
and the stimulant caffeine. (That you end up with something very
non-amphetamine like is neither here nor there.) The combination drugs
were called "Dexatrim" or Dexa-whosis (as in Dexedrine) for a reason,
namely, to assert its similarity in the minds of prospective buyers.
However, caffeine has not been in OTC diet pills for many years per
order of the FDA, which stated that there was no evidence of efficacy
for such a combination.
From Goodman and Gilman's The Pharmacological Basis of Therapeutics:
Caffeine in combination with an analgesic, such as aspirin,
is widely used in the treatment of ordinary types of
headache. There are few data to substantiate its efficacy
for this purpose. Caffeine is also used in combination with
an ergot alkaloid in the treatment of migrane (Chapter 39).
Ergotamine is usually administered orally (in combination
with caffeine) or sublingually [...] If a patient cannot
tolerate ergotamine orally, rectal administration of a
mixture of caffeine and ergotamine tartarate may be
attempted.
The bioavailability [of ergotamine] after sublingual
administration is also poor and is often inadequate for
therapeutic purposes [...] the concurrent administration of
caffeine (50-100 mg per mg of ergotamine) improves both the
rate and extent of absorption [...] However, there is little
correspondence between the concentration of ergotamine in
plasma and the intensity or duration of therapeutic or toxic
effects.
Caffeine enhances the action of the ergot alkaloids in the
treatment of migrane, a discovery that must be credited to
the sufferers from the disease who observed that strong
coffee gave symptomatic relief, especially when combined
with the ergot alkaloids. As mentioned, caffeine increases
the oral and rectal absorption of ergotamine, and it is
widely believed that this accounts for its enhancement of
therapeutic effects.
Nowadays most of researchers believe that the stimulatory actions are
attributable to the antagonism of the adenosine. Agonists at the
adenosine receptors produce sedation while antagonists at these sites,
like caffeine and theophylline induce stimulation, and what is even
more important, the latter substance also reverse agonists-induced
symptoms of sedation, thus indicating that this effects go through
these receptors.
Another possibility, however, is that methylxanthines enhance release
of excitatory aminoacids, like glutamate and aspartate, which are the
main stimulatory neurotransmitters in the brain.
As to the side effects: methylxanthines inhibit protective activity of
common antiepileptic drugs in exptl. animals in doses comparable to
those used in humans when correction to the surface area is made. It
should be underlined, that although tolerance develop to the
stimulatory effects of theo or caffeine when administered on a chronic
base, we found no tolerance to the above effects . This hazardous
influence was even enhanced over time. Therefore, it should be
emphasized that individuals suffering from epilepsy should avoid, or
at least reduce consumption of coffee and other caffeine-containing
beverages.
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