The relief from fatigue
that tea provides is a big reason for its popularity. This is due to
caffeine, and caffeine has been a matter of controversy. It is a stimulant
that has been shown to speed reaction time, increase alertness, and improve
concentration. The physical effects include stimulation of digestive juice,
the kidneys, and the metabolism in ways that possibly help eliminate toxins.
An increasing of mental alertness, shortening of reaction time, and improving
efficiency of muscle action is brought about by caffeine's stimulation of the
heart and respiratory system, bringing more oxygen to the brain.
There has been much
concern in the United States recently about the possible dangers of caffeine. As
regards tea, it should be noted that all types of tea contain less caffeine
than coffee. The caffeine content of some of our teas is available here.
Caffeine tolerance varies
greatly among individuals, and an excess of it is toxic. Some research has
shown a possibility that caffeine can interfere with fetal development,
including lowering birth weight and contributing to skeletal and other
abnormalities. Until they reach the age of seven or eight months, babies
cannot get rid of caffeine metabolites, and traces of caffeine can appear in
breast milk too. Due to 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 half as much. Twenty cups of green tea yield 240
milligrams, or about 12 milligrams per cup.
Because tea bags contain
broken leaves of smaller size, they produce an infusion with more caffeine
than loose tea does. This is also true of very fine loose tea.