4.2.4 Caffeine
Cola-type soft drinks, which contain caffeine, currently
have the largest share of the beverages market in
Australia (Euromonitor International 2006). Caffeine is a
mildly addictive stimulant drug which occurs naturally in
tea, coffee and chocolate but soft drinks are the main
source of caffeine in children’s diets (Ellison et al. 1995;
Nestle 2000). Levels of caffeine in soft drinks occur in the
range of 40–50 mg per 375 ml can. Higher amounts are
found in energy drinks (80–120 mg per can, equivalent
to one cup of strong coffee), which are forming an
increasing share of beverages consumed. The current
Australian Food Standards Code allows the addition of
caffeine in cola-type soft drinks, flavoured cordials and
flavoured syrups, and the total caffeine content must not
exceed 145 mg/kg (36 mg / 250 ml serve) in the drink as
consumed (Smith et al. 2000).
The link between caffeine in soft drinks and bone health
has been indicated in the previous sub-section. In addition,
several studies have found a connection between cola
drinks and kidney stones (Rodgers 1999; Massey and Sutton
2004) and the US National Institutes of Health currently
recommend that people trying to take preventative
action should limit their caffeine consumption, including
that from cola beverages (National Kidney and Urologic
Diseases Information Clearinghouse 2004).
More immediate effects of caffeine on health are also
apparent. Caffeine sensitivity (the amount of caffeine
that will produce an effect in someone) varies from
person to person. On average, the smaller the person,
the less caffeine needed to produce side effects. The
short-term affirming effects of caffeine include increased
energy and attention, enhanced mood and motivation as
well as enhanced motor activity, even at low doses
(20–200 mg) (Smith et al. 2000). Nevertheless there are
considerable negative effects of caffeine consumption,
particularly in children and young adults. Negative
effects, especially in young children, include disturbed
sleep patterns, bedwetting and anxiety, from even
modest consumption of caffeine-containing soft drinks.
Withdrawal symptoms such as headache, fatigue,
decreased alertness, depressed mood and irritability can
be experienced 6–24 hours after caffeine abstinence,
again even for low doses (Juliano and Griffiths 2004).
Avoidance of withdrawal symptoms plays a central role in
the habitual consumption of caffeine by increasing the
reinforcing effects of caffeine and preference for tastes
paired with caffeine (Juliano and Griffiths 2004). This is
of particular concern for soft drinks sold to children and
adolescents as even low doses can suppress withdrawal
symptoms (Evans and Griffiths 1999) which may lead to
increased soft drink consumption.