Caffeine and Nutrition: an Overview - Caffeine: Chemistry, Analysis, Function and Effects - page 6

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Figure 1.1 Origin, chemical structure, and consumption of caffeine. (A) The coffee

plant, Coffea arabica, with some green seeds that will mature and be
roasted and ground to generate the coffee powder used to prepare the
coffee infusion, which is rich in caffeine. (B) The chemical structure of the
caffeine molecule, 1,3,7-trimethylxanthine. (C) Consumption of small
amounts of coffee infusion is believed to improve attention, and drinking
coffee has become a pleasant social habit in almost all cultures. In this
picture, one of the authors (RCAG) is drinking a small cup of coffee
during a break from writing this text (unpublished pictures from the
authors' lab).

(1988). For recommendations about consumption of caffeine-containing

energy drinks, see Higgins et al (2010).

1.2 Pharmacodynamics and Pharmacokinetics of Caffeine
After ingestion, caffeine is rapidly absorbed in the gastrointestinal tract in both
humans and in laboratory animals (Magkos and Kavouras 2005). When plasma
caffeine concentrations after caffeine oral intake are compared with those after
intravenous administration, they vary over time with comparable features,
suggesting similar pharmacokinetics in the two routes of administration (Arnaud
1993). Concerning its action on the central nervous system, caffeine seems to pass
freely from blood to brain and also exerts a dose-dependent, protective effect
against the blood-brain barrier disruption found in degenerative diseases of the
central nervous system, like Alzheimer's disease and Parkinson's disease (Chen
et al 2010). The stimulant effects of caffeine on the central nervous system are
primarily the result of its role in the blockade of adenosine receptors (mostly on
the high-affinity A 1 and A 2A receptors), the inhibition of cAMP phosphodiester-