Caffeine as an Ingredient in Sugar Sweetened Beverages - Caffeine: Chemistry, Analysis, Function and Effects - page 23

were reported as 17 mg per day. It is suggested that cola flavored SSB provide
around 62% of this intake (Desbrow et al 2004).
Is the popularity of caffeinated foods mere coincidence? Is the flavor coffee,
chocolate, tea and cola soft drinks such that without caffeine they would still
be widely consumed? Or is the popularity of caffeine containing foods due to
the influence of caffeine in the body?

d n 0 t 2 n g | 2

2.2 Caffeine in the Body
Within 20 minutes of ingestion, 90% of the caffeine (Figure 2.1) consumed is
removed from the stomach (Heckman et al 2010), the majority to be processed
by the liver to enable absorption into the bloodstream (Heckman et al 2010).
Once caffeine enters the bloodstream it exhibits effects on the central nervous
system and metabolism. Half of the dose of caffeine is eliminated from the
body of healthy humans in approximately 4-5 hours (Mandel 2002). The acute
effects of caffeine on the human body have been identified as stimulating both
mental function and the sympathetic neural system. Caffeine is a non-selective
adenosine receptor antagonist (competitive inhibitor), primarily inhibiting
adenosine receptors A 1 and A 2a . Adenosine A 1 receptors are most abundantly
found in the hippocampus, the cerebral cortex, the cerebellar cortex and the
thalamic nuclei in the brain, whereas the adenosine A 2a receptors are found in
basal ganglia areas of the brain where it has a role in regulation of dopamine
release. Adenosine has an inhibitory effect on the central nervous system and
therefore caffeine acting as a competitive inhibitor at adenosine receptors A 1
and A 2a effectively acts as a stimulant (Daly and Fredholm 1998). Thus the
stimulatory effects of caffeine on the body are mainly due to this inhibition of
adenosine (Mandel 2002) (Figure 2.2).
Improvements in concentration and alertness upon consumption of caffeine
are two benefits in mental functions that have been well documented, even
amongst the sleep deprived. These effects have been identified with

Figure 2.1

Structure of caffeine (1,3,7-trimethylxanthine). This figure shows the
chemical structure of caffeine. Caffeine is an alkaloid which means it
contains nitrogen and hydrogen ions; it also has a methyl group attached
to the first, third and seventh nitrogen group giving it the chemical name
of 1,3,7-trimethylxanthine.