0The New Complete Book of Food
NOTE: Theophylline, the primary stimulant in tea, relaxes the smooth muscles lin-
ing the bronchi (the small passages that carry air into the lungs). As a drug, theophylline is
effective in relieving asthmatic spasms, but the relatively low concentrations in brewed tea
are too small to produce therapeutic results.
Lower risk of some kinds of cancer. In 1991, a number of scientific teams at the Fourth Chemi-
cal Congress of North America announced the identification of chemicals in teas that show
positive results in laboratory studies in which laboratory animals given green and black
tea have lower rates of skin tumors, esophageal tumors, gastrointestinal tract tumors, and
tumors of the lung, liver and pancreas. Eight years later, in January 1999, Purdue Univer-
sity researchers released a study showing that EGCg, a compound in green tea, inhibits an
enzyme required for cancer cell growth, killing cancer cells in laboratory dishes without
harming healthy cells. The Purdue findings suggest that drinking four cups of green tea a day
may produce a lower overall risk of cancer. NOTE: People who drink tea when it is very hot
(131°F to 153°F) have a higher risk of esophageal cancer than do people who drink tea at a
temperature of 95°F to 117°F. The higher rate of cancer is almost certainly due to the tissues
being injured repeatedly by the extremely hot liquid.
Lower risk of cardiovascular disease (heart attack and stroke). Numerous studies have sug-
gested that consuming moderate amounts of tea (five cups per day) reduces both overall
mortality (death from all causes) and the risk of death from cardiovascular disease. There are
several possible explanations for this finding. For example, in 2008, a report from INSERM,
France’s national institute for medical research, found that women who drank three or
more cups of tea a day were 11 percent less likely than non–tea drinkers to have cholesterol
plaques (deposits) inside their arteries. In addition, drinking tea appears to increase the abil-
ity of blood vessels to expand, an important factor in protecting against blood clots that may
block the vessel, leading to a heart attack or stroke. In a clinical trial, one group of patients
with coronary artery disease and mildly elevated cholesterol levels were each given four to
six cups of black tea a day for at least four weeks, while a second group got either a bever-
age with the equivalent amount of caffeine or plain hot water. The blood vessels of patients
who drank tea daily dilated more effectively. Some researchers attribute this effect to the
catechins in tea.
Many researchers do not consider these results conclusive either because many studies
showing lower mortality were too small or because tea consumption in the general popula-
tion was too low to allow reliable comparisons between tea drinkers and non–tea drinkers.
As a result, while both black and green teas (and presumably white teas) appear to be protec-
tive, further research is needed to provide firm conclusions about tea and heart health.
Lower risk of some forms of cancer. Animal studies suggest that both green and black teas
may reduce the risk of cancers of the skin, lung, mouth, esophagus, stomach, colon, pan-
creas, bladder, and prostate, while white tea and green tea reduce the incidence of intestinal
polyps. Again, the effects are attributed to the flavonoids (catechins) in the teas. However,
human studies have produced inconsistent results. For example, while some studies show a
decreased risk of colon cancer among tea drinkers, others do not. In general, the assumption
is that further evidence is required before linking tea consumption and cancer prevention.