The
victory over fatigue that tea provides is a big reason for its
popularity. Caffeine is what does it, and caffeine has been a matter
of controversy. A stimulant, caffeine has been shown to speed
reaction time, increase alertness, and improve concentration.
The
original intake of caffeine causes the body to create stimulant
chemicals, catecholamines, that relay nerve impulses to the brain.
The height of this effect lasts from 15 to 45 minutes. After six
hours the body has eliminated half of the caffeine.
If
this can be described as a spiritual benefit, then the physical
effects include stimulation of digestive juice, metabolism, and the
kidneys in ways that possibly help eliminate toxins. Also,
stimulation of the heart and respiratory system brings more oxygen
to the brain, thus increasing mental alertness, shortening reaction
time, and improving efficiency of muscle action.
Because there has been mush concern in the United States about
possible dangers of caffeine, it should be noted that all types of
tea contain less caffeine than coffee. Green tea has less than
black.
Caffeine tolerance, however, varies greatly among individuals, and
an excess of it is toxic. Of greater concern is the fact that some
research has shown a possibility that caffeine can interfere with
fetal development, including lowering birth weight and contributing
to skeletal and other abnormalities. Babies cannot get rid of
caffeine metabolites until they reach the age of seven or eight
months and traces of caffeine can appear in breast milk, also. In
light of these concerns, pregnant and nursing mothers should limit
or avoid any beverage with caffeine, including tea.
Caffeine content is also affected by the length of the infusion in
water: Black tea infused for 5 minutes yields 40-100 milligrams,
whereas a 3-minute infusion produces 20-40 milligrams, or milligrams
per cup, according to Chen Binfan of the Fujian Tea Society.
Tea
bags, which contain broken leaves of smaller size, produce an
infusion with more caffeine than does loose tea. This is also true
of very fine loose tea.
