Soltalk May 2019 | Page 44

Doctor’s notes
Dr Rik Heymans is a general practitioner in Nerja and writes
on developments in the world of medicine
Cup of tea?
250ml) followed by green (35-70 mg), oolong (50-75 mg), and
black teas (60-90 mg). The same size cup of coffee contains
about 100 mg caffeine. Herbal teas will not contain caffeine, or
far less.
The potential health benefits of tea consumption have been
the subject of thousands of studies, many of which have
examined the role of polyphenols. Polyphenols (including
flavonoids) are a class of phytochemicals believed to give tea
(as well as coffee, certain vegetables, fruits, and grains) its
antioxidative properties, flavour, colour, and smell. These
strong antioxidants may reduce the oxidation of low-density
lipoprotein (LDL) cholesterol and lower the risk for heart
disease. They may also have anti-carcinogenic effects
stemming from their potential to mediate the oxidation of
DNA and by inducing glucuronosyltransferases, thereby
helping to eliminate toxicants and carcinogens.
A long-standing debate about milk and tea is not just about
whether the milk should be added to the cup first or vice versa.
More than a decade ago, a small study suggested that adding
milk to black tea negates the vascular benefits of tea, probably
by promoting the formation of complexes with tea catechins. A
small recent study also found that adding milk to black tea
alters the favourable impact of tea consumption on vascular
function and blood pressure—for as-yet unknown reasons.
Current evidence points to the many potential benefits of tea
drinking—some of which appear to be associated with its
antioxidative properties, whereas others may simply coincide
with a healthy lifestyle. Nevertheless, the uneven quality of the
data and the diverse types of studies make it difficult to draw
firm conclusions. Which teas have the strongest health benefits
(or risks) and why remains unknown. Researchers still need to
address many facets surrounding tea and health, including the
ideal brewing methods; the addition of substances; the
frequency, amount, and duration of consumption; and
whether a tea leaf's health potential declines as it ages.
Tea polyphenols may also promote favourable intestinal
bacterial flora and inhibit reactive oxygen species associated
with age-related diseases. Currently, some of the most
promising avenues for research on tea consumption are related
to the positive effects of flavonoids on coronary artery disease
and stroke. Total intake of flavonoids and flavones is associated
with lower risks for fatal cardiovascular disease. All types of tea
derived from the Camellia sinensis plant contain caffeine;
however, various factors (eg, tea leaf processing, tea type, brew
method, and strength) affect the amount of caffeine in tea. The
most widely reported estimates reveal that the lowest amount
of caffeine is found in the yellow and white teas (30-55 mg/
Furthermore, a significant proportion of studies were
conducted in Asian populations, where tea drinking is
widespread. Future research should include more diverse
populations of tea drinkers. However, apart from the benefits
which may come from drinking tea, there are some drawbacks
too: in a large population-based case-control study it was
observed that drinking very hot tea significantly increased the
risk for oesophageal squamous cell carcinoma in a sample of
high-risk Chinese men, especially in those who also consume
alcohol. It seems that it is plausible that the observed increased
oesophageal cancer risk is attributable to thermal injury caused
by drinking very hot tea rather than to the tea per se, and tea
drinkers were encouraged to allow their tea to cool before
consuming. The International Agency for Research on Cancer’s
view is that consuming hot beverages of any type is "probably
carcinogenic."
© Dr RIK HEYMANS
c/ Angustias 24, Nerja.
Tel: [phone]
42