Tea health
eht tuobA
overview
aeT fo etutitsnI no
Tea remains the most widely consumed beverage in the
world - after water. New research highlights the health
1
benefits sof
tea
sen
erawand
a etoplaces
morp oitt ssecond
i noissimonly
s’aeTtofowater
etutitsas
nI the
notpiL ehT
2
healthiest hydration fluid in the world.
hcraeser ruO .puc ot hsub morf aet fo gnidnatsrednu dna
.stfieneb htlaeh sti dna seitreporp sti ,edam si aet woh no sesucof
The following tea information aims to answer many of the
fo stsisnoc etutitsnI eht ,KU ,koorbnrahS ni sretrauqdaeh htiW
frequently
asked questions regarding tea and health.
ni detacol sertnec hcraeser morf strepxe cfiitneics lanoitanretni
egareveb yek ni dna ,ayneK & aidnI ,snoiger gniworg aet rojam
anihC dna napaJ ,SU – stekram
What is tea?
Camellia Sinensis leaves
Green, What
black
and is
oolong
What
is tea?
tea?tea
are produced from the same
Green,
black
and
oolong
tea
arelies
produced
the same
plant, Camellia sinensis. The difference
in the wayfrom
they are
plant, Camellia sinensis. The difference lies in the way they
processed.
The black
Camellia
sinensis
is anproduced
evergreenfrom
shrub.
Green,
oolongplant
tea are
the same
are processed.
Theand
Camellia
sinensis
plant is an
evergreen
Its leaves,
if
not
dried
quickly
after
picking,
soon
begin
to
wilt
shrub.
Its
leaves,
if
not
dried
quickly
after
picking,
plant, Camellia sinensis. The difference lies in the waysoon
they are
begin
to
wiltThe
andmajor
oxidise.
The
majortea
step
in
making
tea
and oxidise.
step
in
making
is
to
stop
the
processed. The Camellia sinensis plant is an evergreen shrub.
is to stop the oxidation process by heating the leaves at
oxidationIts process
by
the leaves
at different
stages
leaves, ifdepending
notheating
dried quickly
after
picking,
begin to leaf
wilt
different
stages
on the
tea
type soon
– flavoured
depending
on
the
tea
type
flavoured
leaf
teas,
green,
teas,
green,
oolong,
white,
black.
and oxidise. The major step in making tea is to stop the
Harvesting
Camellia Sinensis leaves
Drying
Harvesting
Shaping
Oxidation (short)
oolong, oxidation
white, black.
process by heating the leaves at different stages
depending
on the tea
Tea and
flavonoids
type - flavoured leaf teas, green, Heating
Black, oolong,
green white,
and oolong
teas
are a rich source of
black.
flavonoid from the polyphenol family (see figure 1).
Black,flavonoids
green and oolong
teas are atorich
source
of flavonoid
Tea
are different
those
found
in most fruitsGreen tea
and
vegetables.
antioxidants
from the polyphenol family (see figure 1). Tea
Oxidation
Shaping
Heating
Heating
Oxidation (short)
Oxidation
Tea and flavonoids
Tea and flavonoids
Drying
Heating
Oolong tea
Heating
Black tea
Heating
flavonoids
are
different
to oolong
those
found
in most
fruits
and
vegetables.
flavonoids
in tea Oolong
can acttea
as antioxidants,
tea
Blacktea
tea
The
types
and
amounts
of flavonoids
found
in tea
Black,
green
and
teas are
a rich
source
of flavonoidWhile theGreen
is not a depending
substitute
for
fruit
and
vegetables,
which
provide
a
wide
range
of
other
antioxidants
and
essential
nutrients,
including
differ
on
the
variety
of
leaf,
the
growing
antioxidants from the polyphenol family (see figure 1). Tea
environment,
processing, manufacturing, particle size
vitaminsflavonoids
and minerals.
are different
those found
in most fruits
and vegetables.
the flavonoids
in teaproduced
can act as antioxidants,
tea
4
of ground tea leaves
and to
infusion
preparation
. Catechins
are While
the main
flavonoids
by the
Camellia
sinensis
plant.
During
the oxidation
enzymatic
activity
allows the
catechins
to beincluding
is not
a substitute
for fruit
and vegetables,
which process,
provide a wide
range of other
antioxidants
and essential
nutrients,
The types
and
amounts
of
flavonoids
found
in
tea
differ
depending
on
the
variety
of
leaf,
the
growing
environment,
polymerised
and
alter
their
structure.
vitamins and minerals.
processing, manufacturing, particle size of ground tea leaves and infusion preparation.4 Catechins are the main flavonoids
•G
reen tea leaves are heated soon after harvesting so undergo minimal oxidation. This stops the enzymatic
produced
the Camellia
sinensis
plant.
During
the
process,
enzymatic
be
activity,
majority
of catechin
flavonoids
and
its green
Thebyretaining
types
and the
amounts
of flavonoids
found
inoxidation
tea differ
depending
oncolour.
the activity
variety allows
of leaf,the
thecatechins
growing to
environment,
polymerised
and alter
their structure.
processing,
manufacturing,
particle size of ground tea leaves and infusion preparation.4 Catechins are the main flavonoids
•
B
lack
tea
undergoes
substantial
oxidation,
which
changes
the colour
of the
from
green to
brown,
• Green
tea
leaves
are
heated
soon
after
harvesting
so the
undergo
minimal
oxidation.
Thisleaves
stops
the
enzymatic
activity,
Camellia sinensis
plant.
During
oxidation
process,
enzymatic
activity
allows
the catechins
to be
and produced
results in by
thethe
polymerisation
of catechins
into theaflavins
and thearubigins
flavonoids.
retaining
the
majority
of
catechin
flavonoids
and
its
green
colour.
polymerised and alter their structure.
• O
undergoes
substantial
oxidation,
which
changes
the
of the
leaves oxidation.
fromthat
green
to
brown,
andblack
resultstea
in activity,
•
Black
olong
tea
istea
a result
of
being
somewhere
in
between
ofThis
green
and
•teaGreen
leaves
areoxidation
heated
soon
afterstopped
harvesting
socolour
undergo
minimal
stopsand
the
enzymatic
therefore
contains
flavonoids
that
are
found
in
both
green
and
black
teas.
the polymerisation
catechinsofinto
theaflavins
and thearubigins
retaining theofmajority
catechin
flavonoids
and its greenflavonoids.
colour.
• Oolong
tea
is
a
result
of
oxidation
being
stopped
somewhere
in
between
of leaves
green from
and black
therefore
• Black tea undergoes substantial oxidation, which changes the
colour that
of the
greentea
to and
brown,
and results in
containsthe
flavonoids
that are of
found
in both
green
and black
polymerisation
catechins
into
theaflavins
andteas.
thearubigins flavonoids.
• Oolong tea is a result of oxidation being stopped somewhere in between that of green and black tea and therefore
contains flavonoids that are POLYPHENOLS
found in both green and black teas.
Non Flavonoid
Polyphenols
Flavanones
citrus
fruit
Flavanones
citrus
fruit
POLYPHENOLS
Non Flavonoid
FLAVONOLS
Polyphenols
tea
apples
onions
FLAVONOLS
tea
apples
onions
FLAVANOLS
tea
apples
wineFLAVANOLS
FLAVONOIDS
Flavones
celery
parsley
tea
apples
CATECHINSwine
Isoflavones Anthocyanins
FLAVONOIDS
soya
red wine
red clover
blueberry
cherry
Flavones
Isoflavones Anthocyanins
celery
soya
red wine
parsley
red clover
blueberry
cherry
Green Tea
Oolong Tea
CATECHINS
Oxidation during
Chemical structure yet
THEARUBIGINS
Green Tea THEAFLAVINS
processing
to be fully identified
Oolong Tea
Black Tea
Black Tea
Oolong Tea
Oxidation
during
Chemical structure yet
THEARUBIGINS
THEAFLAVINS
Figure 1. The
family (compiled by the Lipton Institute ofprocessing
Tea)
to Polyphenol
be fully identified
Figure 1. The Polyphenol family (compiled by the Lipton Institute of Tea)
Black Tea
Black Tea
Oolong Tea
?
?
Figure 1. The Polyphenol family (compiled by the Lipton Institute of Tea)
GREEN TEA
BLACK TEA
Catechins (70%)
Theaflavins (12%)
Flavonols (10%)
Catechins (8%)
Polymeric
flavonoids (20%)
Flavonols (10%)
Thearubigins (70%)
Figure 2.
2. The
The type
type ofofflavonoids
found
in green
vs black
tea (compiled
by the
Institute
of Tea)
Figure
flavonoids
found
in green
vs black
tea (compiled
byLipton
the Lipton
Institute
of Tea)
Five catechin flavonoids (major flavonoids in the tea plant and green tea) have been investigated and identified as:4
Five
catechin
• Catechin
- Cflavonoids (major flavonoids in the tea plant and green tea) have been investigated and
1
identified
as:
• Epicatechin - EC
Epigallocatechin
•• Catechin
- C - EGC
•• Epicatechin
- EC - ECG
Epicatechin Gallate
•• Epigallocatechin
- EGC
Epigallocatechin Gallate
– EGCG main catechin in Camellia sinensis and green tea
• Epicatechin Gallate - ECG
• Epigallocatechin Gallate – EGCG main catechin in Camellia sinensis and green tea
During the black tea process, the catechins are enzymatically polymerised. Two polymer groups of catechins have been
During
black teaand
process,
the catechins
are enzymatically
polymerised.
Two polymer groups of catechins
identifiedthe
- theaflavins
thearubigins.
Four theaflavins
(TF) structures have
been ascertained:
have been identified - theaflavins and thearubigins. Four theaflavins (TF) structures have been ascertained:
• Theaflavin - TF
•• Theaflavin
- TF
Theaflavin 3-gallate
- TF3G
•• Theaflavin
3-gallate
- TF3G
Theaflavin 3’-gallate - TF3’G
• Theaflavin 3’-gallate - TF3’G
Theaflavin 3,3’-gallate
- TFDG
•• Theaflavin
3,3’-gallate
– TFDG
1,3
An
cup
black
or green
tea provides
of flavonoids.
3,4
An average
average cup
of of
black
or green
tea provides
140-300140-300mg
mg of flavonoids.
Flavonoids have been shown to have a strong
antioxidant capacity in vitro. Several human studies have also found that black and green tea consumption can increase
plasma antioxidant capacity.5,6 Whether tea flavonoids are solely responsible for this increase, or other tea components may
also have a significant effect is a matter of current investigation. Antioxidants may help the body protect from free radical
damage so the antioxidant properties of tea may be beneficial for health. However more research in this area are needed
to confirm these findings as well as to understand the bioavailability and the physiological relevance of tea flavonoids.
Free radicals
Free radicals are generated in the body as a result of chemical reactions during normal
metabolic processes as well as in response to excess pollution, UV sunlight and exposure to
cigarette smoke. Chronic damage by free radicals to DNA, lipids and proteins is one factor
thought to contribute to the development of many chronic diseases such as cardiovascular
disease (CVD), cancer and neurodegenerative diseases. Endogenous antioxidant defences
may not be sufficient to scavenge free radicals completely. Consuming foods rich in dietary
antioxidants may therefore, help the body’s ability to protect itself against free radical
damage.11,12
Figure
Figure
3. Flavonoid
Figure
3.
Flavonoid
3.
Flavonoid
content
of content
selected
of selected
ofof
beverages
selected
beverages
beverages
Figure
3.content
Flavonoid
content
selected
beverages
-FlavonoidAverage
mg
permg
g per
AOXAOX
- Average
AOX
mg
-- Average
per
100
g100
per
100
gg
Average
mg
AOX
Average
mg
per
100100g
160 160 160
160
140 140
139 139
140
140
139
139
120 120
120
120
118 118
100 100
100
100
80 80
80
80
60 60
60
60
40 40
40
40
20 20
20
20
0
0
13
*and13foods
*foods1313**
and and
foodsfoods
and
*Please
*Please
note:
*Please
note:
whilewhile
note:
the flavonoids
the
while
flavonoids
the
in
teain can
tea in
can
*Please
note:
while
the flavonoids
flavonoids
in tea
tea can
can
act asactantioxidants,
as act
antioxidants,
tea istea
notis anot
tea
substitute
isais substitute
not
substitute
for for
act as
as antioxidants,
antioxidants,
tea
not aa for
substitute
for
118
118
fruit fruit
and and
vegetables,
fruit
vegetables,
and
which
which
provide
which
provide
a wide
provide
a wideaa wide
fruit
and vegetables,
vegetables,
which
provide
wide
rangerange
of other
range
of
other
antioxidants
of
antioxidants
and and
essential
essential
and
range
of other
other antioxidants
antioxidants
and essential
essential
vitamins
vitamins
and
vitamins
and
minerals.
minerals.
and
addition,
In addition,
In
addition,
the the
vitamins
andInminerals.
minerals.
Inthe
addition,
the
30 30
measurement
measurement
measurement
of antioxidant
of antioxidant
of
content
content
of content
of
of
measurement
of antioxidant
antioxidant
content
of
30
30
10 10
10
10
3
individual
individual
foods
individual
foods
doesfoods
does
not necessarily
not
does
necessarily
not
reflect
reflectreflect
individual
foods
does
not necessarily
necessarily
reflect
3
33
0 0
bioavailability
bioavailability
their
or physiological
or physiological
or
effect.
effect. effect.
their bioavailability
bioavailability
or physiological
physiological
effect.
00 theirtheir
00
Green
Green Black
Green
Black
Orange
Blackcurrant
Coffee Coffee
tea tea
Black
Orange
tea
Raw Raw
Blackcurrant
Raw
Blackcurrant
Coffee
Green
Black
tea Orange
Orange
Raw
Blackcurrant
Coffee
tea tea tea
broccolibroccoli
juice juice broccoli
juice
juice juice juice
tea
juice
broccoli
juice
Figure 3. Flavonoid content of selected beverages11*
Dispelling
Dispelling
Dispelling
thethe
myths
the
myths
myths
Dispelling
the
myths
BlackBlack
tea Black
istea
not
is tea
not
a good
isisa not
good
source
aa good
sourcesource
FALSE
FALSEFALSE
Green
Green
and
Green
and
blackblack
and
tea black
tea
bothboth
tea
come
come
from
come
from
the from
the
same
same
the
plant
same
plant
- Camellia
plant
-plant
Camellia
-- Camellia
FALSE
Black
tea
not
good
source
Green
and
black
tea both
both
come
from
the
same
Camellia
of flavonoids.
of flavonoids.
of
sinensis.
sinensis.
The
sinensis.
The
totaltotal
The
flavonoid
total
content
content
ofcontent
black
of black
and
of
and
green
green
and
teagreen
isteasimilar
is tea
similar
of flavonoids.
flavonoids.
sinensis.
Theflavonoid
total flavonoid
flavonoid
content
of black
black
and
green
tea isis similar
similar
(see(see
Figure
Figure
(see
2) Figure
however
2) however
2)
they
they
contain
contain
they
contain
different
types
different
types
of flavonoids
types
of flavonoids
of
that that that
(see
Figure
2) however
however
theydifferent
contain
different
types
of flavonoids
flavonoids
that
maymay
havehave
may
different
different
have
modes
different
modes
of
modes
action
of
action
and
of
action
and
bioavailabillity
bioavailabillity
and
bioavailabillity
(see
(see
figure
figure
(see
1).
figure
1).
1).
may have different modes of action and bioavailabillity (see figure 1).
Human
Human
studies
Human
studies
have
studies
have
shown
shown
have
anshown
increase
an increase
an
blood
in blood
antioxidant
in
antioxidant
antioxidant
capacity
capacity
capacity
Human
studies
have
shown
aninincrease
increase
in blood
blood
antioxidant
capacity
5,6
afterafter
consumption
consumption
after
of black
of black
tea.
of
black
tea.
tea.
after consumption
consumption
of 5,6
black
tea.5,65,6
Drinking
Drinking
tea
Drinking
causes
tea causes
tea
dehydration.
causes
dehydration.
dehydration.
FALSE
FALSEFALSE
Tea Tea
is anisimportant
Tea
an important
isis an
source
source
ofsource
fluids
of fluids
and
of
and
doesdoes
and
not does
not
cause
not
dehydration
cause
dehydration
dehydration
FALSE
Tea
an important
important
source
of fluids
fluids
and
doescause
not
cause
dehydration
Drinking
tea
causes
dehydration.
7
7
77
in regularly
in regularly
in
regularly
consumed
consumed
amounts.
amounts.
amounts.
Independent
Independent
Independent
scientists
scientists
have
scientists
have
placed
placed
have
inconsumed
regularly
consumed
amounts.
Independent
scientists
have placed
placed
2
22
tea second
tea second
tea
only
second
only
to water
to
only
water
as
to
water
as best
theas
best
hydration
the
best
fluidfluid
and2 and
recommend
fluid
and
tea
second
only
tothe
water
as
thehydration
best hydration
hydration
fluidrecommend
and recommend
recommend
up to
up2tolitres
up
2 litres
to
of 22tea
of
litres
per
teaof
per
day.
tea
per
up
to
litres
of
teaday.
per day.
day.
Tea Tea
contains
contains
Tea
contains
the
same
same
the
amount
same
amount
amount
FALSE
FALSEFALSE
Tea Tea
typically
typically
Tea
typically
contains
less
contains
less
thanthan
half
less
the
than
the
half
caffeine
the
caffeine
per
cup cup
compared
per
cup
to to to
FALSE
Teacontains
typically
contains
lesshalf
thancaffeine
half
theper
caffeine
percompared
cup compared
compared
to
Teathe
contains
the
same
amount
of caffeine
of caffeine
of
coffee.
as coffee.
as
coffee.
coffee.coffee.
coffee.
ofascaffeine
caffeine
as coffee.
coffee.
Tea
and
caffeine
TeaTea
and
Tea
and
caffeine
and
caffeine
caffeine
There is a great deal of consumer confusion surrounding caffeine and tea. Caffeine is an alkaloid that can be found
quantities
coffee,
tea,
chocolate
and
cola
based
drinks.
the
of
caffeine
inin
depends
There
There
is ain
There
great
isvarying
a great
deal
isis aa great
deal
of
consumer
ofdeal
consumer
of
consumer
confusion
confusion
confusion
surrounding
surrounding
surrounding
caffeine
caffeine
and
caffeine
and
tea.
tea.
Caffeine
and
tea.
isCaffeine
anisHowever,
alkaloid
an alkaloid
isis an
alkaloid
that
canlevel
can
be
that
found
be
can
found
be
in
found
in varying
varying
There
great
deal
of in
consumer
confusion
surrounding
caffeine
andCaffeine
tea.
Caffeine
anthat
alkaloid
that
can
bevarying
found
intea
varying
on many factors, including the type of tea, brewing time, quantity of tea leaves used and the size of tea leaves.
quantities
quantities
quantities
intypical
coffee,
in coffee,
in
tea,
coffee,
tea,
chocolate
chocolate
tea,
chocolate
and and
cola
cola
based
and
cola
drinks.
based
drinks.
However,
drinks.
However,
the the
levellevel
the
of
of
level
caffeine
of
tea
in of
depends
teainstant
in
tea
on
many
on many
on
factors,
many
factors,
factors,
quantities
in
coffee,
tea,
chocolate
andbased
cola
based
drinks.
However,
the
level
ofincaffeine
caffeine
independs
tea depends
depends
on
many
factors,
A
cup
of tea
contains
approximately
half
the However,
caffeine
of
acaffeine
typical
cup
coffee
(see
Table
1).
including
including
including
the
the
typetype
of
the
of
type
tea,
brewing
of
tea,
brewing
time,
quantity
time,
quantity
ofquantity
tea
of leaves
teaof
leaves
tea
used
leaves
used
and and
used
the the
size
and
ofthe
tea
ofsize
leaves.
teaof
leaves.
tea
A leaves.
typical
A typical
cup
AA typical
cup
of tea
ofcup
contains
teaof
contains
tea
including
thetea,
type
ofbrewing
tea,time,
brewing
time,
quantity
of
tea
leaves
used
andsize
the
size
of
tea
leaves.
typical
cup
of
tea contains
contains
Tea health overview 15-06-2007 06:34 Pagina 5
Caffeine
in the
moderation
i.e.
to
per
dayTable
has
no adverse
effects on health and may have
approximately
approximately
approximately
half half
the
caffeine
half
the
a of
typical
a typical
of
cup
aa typical
cup
of 300-400mg
instant
ofcup
instant
of
coffee
instant
coffee
(see
coffee
(see
Table
(see
1). Table
1).
1).
approximately
halfcaffeine
theofcaffeine
caffeine
ofup
typical
cup
of
instant
coffee
(see
Table
1).
beneficial effects on mood, mental and physical performance. Moreover, a number of caffeine reviews
have demonstrated that caffeine at levels found in commonly consumed beverages is not dehydrating3. New
Caffeine
Caffeine
in
Caffeine
moderation
in moderation
in
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1.
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caffeine
content
of
beverages
as
consumed
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doctor.
Beverage
Caffeine content
Instant coffee
75mg/190ml cup
Brewed coffee (filtered or percolated)
100-115mg/190ml cup
Decaffeinated coffee
4mg/190ml cup
Tea
50mg/190ml cup
Cola drinks
11 - 70mg/330ml can
Hot chocolate
1.1 - 8.2mg/200ml serving
Energy drinks (with added caffeine or guarana)
28 - 87mg/250ml serving
Table 1. The caffeine content of beverages as consumed7,8
Tea and hydration
Tea and hydration
Independent scientists agree that tea is an excellent hydration fluid5,6. A healthy adult should aim to consume
a daily intake of 2.2 to 2.5 litres of fluid every day7. It is a common myth that tea acts as a diuretic because of
its caffeine content and may therefore compromise hydration. Large amounts of caffeine taken in one sitting
(i.e.250-500mg) can increase urine output and increase the risk of dehydration, however this has not been
seen when caffeinated drinks are consumed3. Review of the literature highlights that:
•O
nly water surpasses tea as the healthiest hydration fluid5,6. A recent clinical study showed that 4 cups of
tea per day are equally hydrating to an equivalent amount of tap water8.
• T ea is hydrating - not dehydrating3,5,6. The levels of caffeine in tea will not dehydrate individuals and it is
recommended to consume up to two litres of tea per day6. A tolerance to caffeine develops so any initial
diuretic effect seen is diminished in people who regularly drink tea3,5.
•H
ydration is fundamental to a number of physical and mental performances - concentration, alertness,
memory, speed and sports performance5,6.
Tea and iron
The flavonoids in tea, similar to the phytates in wholegrain cereals, have been shown to be potential inhibitors
of iron absorption from non-animal sources (non-haeme iron). Tea drinking does not adversely affect iron
status in healthy individuals with no risk of iron deficiency9,10. Groups at risk of low iron status such as
vegetarians, pregnant women and teenage girls, would be advised to choose foods rich in iron and consume
vitamin C rich foods to enhance non-haeme iron absorption. Foods containing iron include red meat, eggs,
legumes, fortified cereals, nuts, seeds and green leafy vegetables. In addition, they would be advised to drink
tea between meals rather than with meals.
Tea and heart health
The largest body of evidence on tea and health relates to cardiovascular disease. Epidemiological
data indicate that individuals who regularly consume green or black tea (without sugar or milk) are more likely
to have better heart health than individuals who do not consume tea as part of a healthy balanced diet and
lifestyle. Two meta-analyses of epidemiological studies have been conducted to determine the overall effect of
black tea drinking and dietary flavonoids on cardiovascular health across populations (from 1966 - 2001)11,12.
Peters and colleagues concluded that consumption of 3 x 240ml cups of black tea per day is associated with
an 11% reduced risk of myocardial infarction12. Evidence on stroke is also strong. One meta-analysis reported
a 21% reduced risk of developing, or dying from, a stroke when three or more cups of tea were consumed13.
Another meta-analysis found a 20% reduction in stroke when higher intakes of dietary flavonoids were
consumed (i.e. 16-47mg per day)14.
There are some confounding factors to consider with regards to tea and heart health:
•
•
•
•
Overall lifestyle habit of the individuals including diet and exercise
Heterogenicity between studies
Publication bias
Social factors
Overall, epidemiological studies support an inverse association between tea intake and risk of cardiovascular
disease and show that people consuming black tea on a regular basis, especially when living a healthy
lifestyle have better heart health. While more research is needed to further establish the specific link between
tea consumption and cardiovascular health, clinical studies have shown that tea flavonoids may improve heart
health through:
• Improving the ability of blood vessels to dilate: Perhaps the strongest available evidence lies in tea’s ability
to relax blood vessels as measured by flow-mediated dilatation (FMD)15,37.
• L owering blood cholesterol: although a popular theory, the evidence is far from conclusive – a few studies
show a cholesterol lowering effect (from 3.8% to 11.3%) of green as well as black tea16,17,38,39.
However, a fair number of studies show no benefit or effect from either green or black tea consumption.
• Inhibition of platelet aggregation: research is still in its infancy18.
At this point in time, the scientific evidence suggests that tea consumption may be a protective factor
in heart health. However, the exact mechanism and dosage has to be identified. Improvement in
endothelial function may be a possible mechanism.
Tea and weight management
In addition to the calorie-free properties of tea (when consumed without sugar and milk), there is evidence
that green tea may be beneficial as part of a weight management programme. This is possibly because
caffeine, and catechins (the particular flavonoids found in green tea), work synergistically to promote body
fat loss and increase energy expenditure19. In Asian populations, research shows that a regular intake
of catechin-enriched green tea reduces total body fat, in particular the fat around the waist, especially
when combined with exercise20. Evidence is still building in Western populations but could have important
implications since excess body fat around the waist relates more strongly to health risks e.g. type 2 diabetes,
than body weight alone.
Tea and dental health
Tea can be a source of fluoride depending on cultivation and preparation factors. It has been estimated
that 1 litre of tea prepared with fluoridated water could provide around 2.2mg of fluoride per day21.
Additionally, some studies have demonstrated tea flavonoids to increase acid resistance of enamel, to act
as an antibacterial and to inhibit human salivary amylase resulting in a reduction of the cariogenic potential
of starch-containing food. These factors may further add to the link between tea and good dental health,
however, further clinical studies are required22.
Tea revitalises both mind and body
Studies have shown consuming a few cups of tea during the day helped to sustain alertness23,24,25. More
recent studies have linked regular tea drinking, at around 4 servings daily, with reduced stress and
increased relaxation26, or an enhanced ability to focus attention27. Ruxton (2008) found that moderate
caffeine intakes of 38mg to 400mg/day, the equivalent intakes of one to eight cups of tea, appeared to
deliver the benefits of improved mood and mental performance without adversely affecting sleep quality28.
Other studies have also shown that moderate intake of caffeine can improve physical performance2,3. Taken
together with data above showing tea to be a good source of hydration, this evidence supports teas ability
to revitalize both mind and body.
Tea and L-theanine
Tea is a unique source of a naturally occurring amino acid L-theanine. L-theanine, at doses found in two
to three cups of tea, has been shown to increase alpha brainwaves which are associated with a relaxed
but alert mental state29. Alpha activity also plays an important role in the ability to focus attention when
performing a cognitive task30. This may help explain why consumers often report to be both revitalized and
relaxed when they consume tea. Research continues in this area.
Diabetes
A new area of research has seen some studies linking tea consumption with a reduced risk of type 2 diabetes.
In a large-scale Chinese survey, drinking one or more cups of tea per day was associated with a 14%
reduction in diabetes risk31. This was confirmed by two met-analyses32,33. It is thought that tea flavonoids could
support normal glucose metabolism by lowering inflammation and by promoting insulin activity but further
human studies are needed before drawing any conclusions.
Cancer prevention
Laboratory tests generally show that tea flavonoids stimulate normal cell turnover and inhibit tumour
development34. While these actions would be expected to help cancer prevention or management in the
long-term, evidence from human trials is lacking. Some surveys have reported a lower risk of colon cancer in
regular tea drinkers, but the results are inconsistent21. Until further research is done, no firm conclusions can
be drawn about cancer prevention properties of tea.
Bone health
A review found that tea had a modest beneficial effect on bone mineral density (BMD), particularly in older
women where significant increases were seen when four or more cups of tea were consumed daily21. A
survey of 1500 elderly women reported that BMD was higher in regular tea drinkers, and declined more
slowly over time, compared with BMD in non-consumers of tea35. These data now need to be confirmed by
controlled trials. It is not clear why tea may affect bone health but there is speculation, based on animal
and cell studies, that the flavonoids in tea, particularly green tea, act by enhancing bone creation and
inhibiting bone breakdown36.
In summary:
Tea has traditionally been consumed because of its perceived health benefits and from the evidence to
date, it is clear that tea consumption does contribute to health:
• T ea as an excellent hydration source is now undisputed. Consumer studies have shown tea to be as
thirst quenching as water and yet more pleasurable. This provides individuals with a more appealing
way to meet their fluid requirements without having to resort to sweetened or carbonated drinks.
• T ea when drunk on its own, without milk or sugar, not only tastes great but contains virtually no
calories. This means that tea is an excellent accompaniment to a healthy balanced diet and lifestyle,
and to a weight management programme.
• T ea is a rich source of flavonoids in the diet. Although large variations in content can occur due to
differing sources, preparation methods etc., it has been shown that in tea drinking populations, tea
provides a significant contribution to daily flavonoid intake.
• In general, the epidemiological data to date points towards a positive association between regular tea
consumption (without milk and sugar) and better heart health. Some studies indicate that tea flavonoids
are associated with better endothelial function, which may explain the benefit to heart health.
• T ea contains L-theanine and low levels of caffeine which together may have positive effects in
helping individuals keeping alert. Tea is the major source of L-theanine and when consumed
independently of tea may help to produce a relaxed and alert mental state. Moreover, caffeine has
been shown to improve mental and physical performance. Taken together data supports teas ability
to revitalise the body and mind.
• T ea contains fluoride and tea flavonoids have demonstrated antibacterial properties. Therefore, tea
drinking may help maintain good dental health.
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liptoninstituteoftea.org
Published January 2012
All information correct at time
of going to press
For health care professionals only