Healthy Properties of Green and White Teas An Update Author S Pastoriza, M Mesias, C Cabrera
Healthy Properties of Green and White Teas An Update Author S Pastoriza, M Mesias, C Cabrera
Healthy Properties of Green and White Teas An Update Author S Pastoriza, M Mesias, C Cabrera
ABSTRACT
Green tea has been consumed for centuries in Japan, China and Morocco. White tea, which is
considered a variety of green tea, is mostly consumed in China and is very appreciated for its flavor.
Currently the consumption of both types of tea has been extended to the western countries even as a
functional ingredient. A group of polyphenols called catechins stands out among their bioactive
components, the most abundant being the (−) epigallocatechin gallate, with high antioxidant power. Teas
also contain other phenolic compounds such as gallic, caffeic, chlorogenic or cinnamic acids, quercetin
and proanthocyanidols, caffeine, theophylline, L-theanine and minerals such as fluorine, manganese or
chromium. Investigations have mainly been focused on their antioxidant potential and their implication in
the prevention and treatment of degenerative diseases. Several studies have evaluated their role in
cardiovascular diseases, body weight control, bone mass increase, protection against neurodegenerative
diseases and improvement of type 2 diabetes, among other pathologies. The main points of controversy
are the design and interpretation of epidemiological and human intervention studies and the lack of
information on catechins availability, metabolism and biotransformation. This review compiles and
analyzes the latest peer-reviewed papers published from 2002 up to February 2017, including systematic
reviews and meta-analyses.
1. INTRODUCTION
Tea is the most consumed beverage in the world after water and is highly valued for its taste and aroma,
its health benefits and for diverse socio-cultural reasons.1 It is obtained by infusion of leaves and shoots
of the species Camellia sinensis var. sinensis. The tea bush is cultivated in more than 45 countries. About
3 billion kilograms of tea are produced and consumed annually1 worldwide and the largest tea producing
countries are China, Japan, Taiwan, Indonesia, Thailand, Sri Lanka, Vietnam, Turkey, Kenya and Russia.
Depending on the processing of the leaf, various types of tea are obtained, such as black tea, Oolong
tea, green tea and white tea.1–3 In black tea, leaves are fermented through oxidation by
polyphenoloxidase enzymes. In Oolong tea, leaves are subjected to a partial fermentation process. In
green tea, the process of fermentation is avoided by the inactivation of the enzymes through a slight
thermal treatment.4 Although there is no consensus on the definition, white tea is considered a green
tea variety produced in very specific places, mainly in Fujian Province (China).5 White tea is made
entirely from leaf buds that are covered with downy and white hairs, from which its name is derived.
The first leaves and buds are selected and subjected to a minimum processing by simple drying. White
tea is highly valued for its organoleptic characteristics, as it provides an infusion with a soft and aromatic
flavor and with floral and fruit notes.2,3 Some authors point out that white tea has less caffeine and
more antioxidant compounds than green tea.2,5 However, other authors have argued that the
composition of both caffeine and antioxidants, defined as the index between total catechins/polyphenols,
is not a criterion of differentiation between green tea and white tea.2,3,6 The variability in the content
of polyphenols and, therefore, in catechins, may be associated with factors such as growing conditions,
climatology, processing, etc7,8 and even the conditions which the infusion is prepared under.9
In black tea, the oxidation process by the polyphenoloxidase enzyme causes remarkable changes in the
chemical composition of the leaf.1 These changes include oxidation of phenolic compounds, which
results in oxidized compounds such as theaflavins and thearubigins, enzymatic hydrolysis of proteins,
oxidative deamination of amino acids, oxidation of lipids and carotenoids, degradation of chlorophyll,
release of caffeine, loss of vitamin C or changes in sensory attributes such as brown-dark color, more
marked empyreumatic aroma and more bitter taste.2 These negative changes are not produced in green
tea and white tea and, therefore, the content of bioactive compounds in both types of tea is higher than
in black tea and, consequently, their beneficial effects on health are more remarkable.
The most abundant catechins in green and white teas are (−) epigallocatechin gallate (EGCG),
representing approximately 59% of the total catechins; (−) epigallocatechin (EGC), which accounts for
19%, (−) epicatechin gallate (ECG) in a proportion close to 13% and (−) epicatechin (EC), around 6% of
the total.12,25,26 According to Hilal and Engelhardt2 and Carloni et al.13 the catechin content in tea
ranges from 9.89 to 17.00 g per 100 g in green tea, from 7.94 to 16.56 g per 100 g in white tea and from
0.74 to 10.00 g per 100 g in black tea. The catechin content is consistent with the fermentation degree,
Due to the beneficial properties of the phenolic compounds and their high content in tea, tea extracts
obtained from the soluble fraction of the unfermented leaves are widely used as an ingredient in food
and cosmetics. Commercial extracts contain different amounts of polyphenols, where about 80% may be
represented by catechins and more than 45% by EGCG. EGCG has an activity against reactive oxygen
species quite superior to vitamins C and E,29 which justifies the high antioxidant capacity associated
with tea.
The more intact the leaves appear, the greater is the flavonoid content. This content decreases with the
manipulation of the leaves, as in powdered tea or during the decaffeination process.12 In addition, the
influence of infusion conditions on the catechin content is significant. Thereby, using almost boiling water
(98 °C) and an infusion time of 7 minutes leads to a high extraction of catechins and polyphenols and,
consequently, to a high total antioxidant capacity.30 Moreover, optimal sensorial characteristics are
achieved under these conditions, while longer infusion times provide bitter taste and excessive
astringency.31
Caffeine acts on the central nervous system by stimulating attention, facilitating the association of ideas
and reducing the sensation of fatigue. Some of the effects caused by caffeine are influenced by the
content of theophylline, which also has inotrope, vasodilator, diuretic and bronchodilator action.12,25
Essential oils, which are abundant in green tea and white tea, facilitate digestion.12 Catechins and in
particular EGCG have low bioavailability when orally ingested.33 Only a small percentage is absorbed at
the level of the small intestine and passes into the bloodstream, reaching maximum plasma
concentrations between 1–3 hours after consumption. Some authors indicate that the secondary
metabolites derived from the intake of flavonoids could be detected in blood and urine. For that reason,
it is thought that the observed biological effects are possibly due to these secondary metabolites rather
than the flavonoids themselves, which are detected in their original form in very low quantities.34 The
bioavailability of phenolic tea compounds has been extensively reviewed by Lambert et al.,35 who
pointed out the need to expand in vivo studies to better confirm the physiological effects of green and
white tea consumption. However, whatever their bioavailability, there are many scientific reports
relating the antioxidant and antiinflammatory effects of EGCG to its ability to modulate mitochondrial
functions, impacting mitochondrial biogenesis, bioenergetic control, etc.36
Several studies have shown that the antioxidant capacity of green tea is higher than that of other types
of tea and other plant products. Using the FRAP (Ferric Reducing Ability of Plasma) method, the total
antioxidant capacity (TAC) of green tea is greater than that of black tea (38 and 17 μM trolox per g tea
per L infusion, respectively).44 Gorjanovic et al.22 determined the TAC in green, white, black and
Oolong tea infusions applying the DPPH (1,1-diphenyl-2-picrylhydrazyl) method, showing values of 4.80
± 0.40, 3.66 ± 0.26, 4.45 ± 0.57 and 3.88 ± 0.06 mM trolox per L, respectively. In addition, according to
the Oxygen Radical Absorbance Capacity (ORAC) method, the TAC of green tea45 is higher than that
of other vegetables such as garlic, spinach and Brussel sprouts (Table 4). In this line, Carlsen et al.46
collected data on TAC measured by the FRAP method in more than 3100 foods, beverages, spices,
herbs and food supplements consumed worldwide. This study proved that the infusion of unfermented
tea leaves had higher TAC values than other products such as orange, grape or tomato juice. Gorjanovic
et al.22 indicated that the antioxidant capacity of the characteristic compounds of green tea and white
tea, determined by the polarographic method, ranges in the following order: EGCG > ECG > EGC >
gallic acid > EC > caffeine.
According to some human intervention studies, a moderate consumption of green tea (1–6 cups per
day) increases the total antioxidant capacity of the plasma and, therefore, promotes a greater protection
of the organism against the oxidative damage caused by free radicals.10,47 For this reason, including the
consumption of green or white tea in the usual diet has been recommended.10,12,48 Biomarkers of the
oxidative status have also shown to decrease with a regular consumption of green tea and
microencapsulated extracts over a period of 1–4 weeks.12 However, it is important to emphasize that
for the effects to be expressed, tea should be consumed as an additional component of a balanced diet
in addition to a healthy lifestyle.
Almajano et al.8 observed a neuroprotective effect of white tea in a study with cell cultures. Results
showed a reduction of the oxidative stress associated with brain damage. This effect was attributed to
the content of catechins and other flavonols. Oxidative stress as a result of the production of reactive
oxygen species (ROS) is known to be an important factor in aging and neurodegenerative disorders such
as Alzheimer’s, Parkinson’s or Huntington’s disease.49
In cell cultures and in experimental animals, EGCG has been shown to protect against carcinogenic
processes induced in different organs, such as skin, lung, stomach, pancreas, duodenum, colon, prostate
and also in breast cancer.39,61–63 This protection has been associated with increased apoptosis or
programmed cell death, which is a key strategy for the removal of neoplastic cells. The protective effect
also includes a decrease in cellular proliferation, its antioxidant and antiinflammatory activities, the
specific induction of detoxifying enzymes and a selective effect on the intestinal microbiota that
facilitates its development.38,39,62,64 In addition, ECGC seems to have an anti-angiogenic effect since it
prevents the growth of blood vessels in tumors.65
Several epidemiological studies carried out in countries with a high tea consumption, such as Japan or
China, suggest that green tea may have a protective effect against certain types of cancer. However, the
results obtained require further investigation since they are not conclusive.63,66,67 In this sense, breast
cancer has been shown significantly less frequent in Asian women with high soybean and green tea
consumption. It suggests that soybean phytochemical compounds may potentiate the inhibitory effect of
green tea on the progression of breast cancer.68
Currently, the chemoprevention of cancer through the use of natural components of diet has acquired
great interest. In this respect, polyphenols ingested through foods and beverages seem to have very
promising effects, although the mechanisms of action are still not well established. Singh et al.69
indicated that EGCG has high potential in cancer prevention with the advantages of being a safe, low-
cost and bioavailable non-toxic natural agent. These authors consider that it could be used alone or in
combination with other treatments, in the prevention and treatment of tumor processes. Traditional
pharmacological treatments can often destroy cancer cells and some healthy cells. However, EGCG
seems to act selectively on the damaged cells.
Studies with experimental animals have evaluated the effects of the administration of catechin
concentrates equivalent to the content of 8–10 cups of green tea. Catechins seem to inhibit the action
of the enzyme that converts angiotensin I into angiotensin II, a potent vasoconstrictor, and therefore its
action is suppressed. However, it is also indicated that the caffeine content of green tea, although low,
may counter the effect of catechins since it could raise the blood pressure.12 Most studies with
experimental animals have observed that green tea catechins decrease the blood pressure.70 Yang et
al.60 concluded that a regular consumption of 120 mL per day of green tea for 1 year significantly
reduces the risk of developing hypertension. In another study conducted in China with 1507 subjects, it
was found that the daily consumption of around 600 mL of green tea for one year reduced the risk of
hypertension compared with the control group of subjects with similar body mass index, diet, and
lifestyle.75 This effect may be due to its vasodilator action, protection against endothelial diffusion and
antioxidant and lipid-lowering properties.
Regarding its action against viruses, the use of green tea on influenza virus is well known, especially at
the earliest stage,84 as well as on the Herpes simplex virus.85 EGCG has also been shown to inhibit
HIV-1 replication by the inhibition of reverse Review Food & Function transcriptase.39 In addition,
EGCG from green tea has received important attention for its effects on Zika virus infection in Brazil.86
According to Mahmood et al.87 the antiviral activity of green tea shows a promising future as a popular
drink and also as a potential therapeutic agent.
Green tea may influence thermogenesis, not only by the action of caffeine, but also because EGCG can
increase energy expenditure by acting on cAMP levels, which suggests a potential effect on body weight
control.96,97 Catechins are known to activate AMP-activated protein kinase (AMPK), an enzyme
involved in the control of energetic metabolism both at cellular and organic levels.96,98 Activation of
AMPK inhibits the process of differentiation of adipocytes and the expression of lipogenic enzymes such
as fatty acid synthetase or acetyl-CoA carboxylesterase. Catechins also have the ability to promote
leptin release and attenuate the symptoms associated with metabolic syndrome. However, the
molecular mechanisms responsible for these changes are unknown.21 In vitro studies have shown that
EGCG interacts with noradrenaline to stimulate the thermogenesis of brown adipose tissue and to
regulate various enzymes related to lipid anabolism and catabolism.99 In this way, extracts of white tea
stimulate lipolysis and, at the same time, inhibit adipogenesis in human adipocytes.100 An inhibition of
the expression of genes involved in gluconeogenesis and in the synthesis of fatty acids, triglycerides and
cholesterol has been observed in rodents.39 A regular consumption of green tea over a period of more
than 10 years has been correlated with a lower percentage of body fat.101,102
4. CONCLUSIONS
The health effects associated with the consumption of green and white teas include protection against
hypertension and cardiovascular diseases, promotion of oral health, control of body weight, antibacterial
and antiviral activity, protection against UV radiation, increase of bone mineral density, and antifibrotic
and neuroprotective properties, among others. These effects are related to their high content of
polyphenols and in particular catechins, where EGCG stands out due to its high antioxidant potential,
which even surpasses that found in vitamins C and E. The effects are also related to the presence of
caffeine and L-theanine, an amino acid with interesting biological effects. Green and white teas may also
be a source of some minerals, including Mn and F. Recent studies indicate that the consumption of green
and white teas may contribute to reduce the risk of some types of cancer. The use of natural
antioxidants such as polyphenols are presented as an interesting proposal for the prevention and
therapy of carcinogenic processes and therefore their mechanisms of action have aroused great
scientific interest. Several authors advise the use of catechins present in tea as a preventive or adjuvant
treatment to other chemical treatments. Although results about EGCG activity are highly promising, a
more precise knowledge of the molecular mechanisms of action in vivo is needed. Following the effects
described on health, green tea has been included in the list of foods with functional properties. Scientific
evidence is very promising but future studies are necessary to test these findings taking into account
environmental, dietary and lifestyle factors. The available data are derived mainly from epidemiological
studies or the extrapolation of results obtained from tests with experimental animals where extracts of
tea rich in catechins, especially with a high content of EGCG, were administered. Several authors agree
on the need to expand in vivo evaluations on the absorption, distribution and metabolism of their main
compounds with antioxidant activity. Moreover, it would be interesting to carry out additional studies
with a habitual consumption extended in time more than studies designed with a very high consumption
during a short period of time. For instance, cancer studies generally compare a low or no consumption
versus a high consumption (even 10 cups per day). Regarding the research carried out with extracts, a
better control of factors such as dose or formulation is necessary. This fact is essential in order to
better identify the product tested and the population which it can exercise the benefit in. In conclusion,
further research and well-designed additional studies (observational, epidemiological and nutritional
Green and white teas have a number of advantages that make them a very good alternative to other
beverages which are widely consumed and less healthy. They are beverages with a pleasant flavor
(flowers and fruit aroma with low levels of bitterness and astringency) that are even commercialized
flavored with other fruits and flowers. They are popular beverages, socially well accepted, economical,
safe and consumed daily by hundreds of millions of people in the five continents. Currently, these teas
are widely used in the preparation of various foods and cosmetics based primarily on the antioxidant
activity, acting as a natural, effective, and safe preservative. However, their consumption in western diets
is still limited and sporadic. Due to the high content of antioxidants, it is recommended that tea
consumption be included in a nutritional, varied and balanced diet. Some authors even define the
consumption of green and white teas as a ‘gift of nature’ for human health.
ACKNOWLEDGEMENTS
This work was supported by the project AGL2014-53895-R from the Spanish Ministry of Economy and
Competitiveness and the European Fund of Regional Development (FEDER). This paper is dedicated to
Prof. Carmen Cabrera, who passed away in 2016. We thank Glenn K. Harding for proofreading the
English-language manuscript.
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Effect Reference
Antioxidant activity 75
Potent antioxidant 69
High anti-free radical activity 128
Prevention of oxidative damage in healthy cells 104
Protection of neurons against oxidative damage 3
Reduction of toxicity generated by H2O2
Activation of Nrf2 factor
Metal chelating activity
Antiangiogenic activity 69
Chemopreventive and anticancer effects 129
Inhibition of cell proliferation (damaged cells) 110
Promotion of healthy cell growth 69
Induction of cell apoptosis 19
Suppression of oncogenic transcription factors 65
Inhibitory effects at metastatic level 130
Inhibition of TNFα expression
Induction and inhibition of enzymes 39
Inhibition of the activity of the chromosomal enzyme telomerase 69
Inhibition of some protein kinases 65
Induction/inhibition of enzymes involved in 60
drugs metabolism
Inhibition of DNA methylation
Effect on RNA expression
Anti-inflammatory activity 19, 69
Detoxifying effect 12, 39
Activity related to lipemia 131
Reduction of intestinal absorption of lipids 19
Promotion of fecal cholesterol excretion 72
Inhibition of hepatic enzymes involved in 73
cholesterol synthesis
Effects against obesity and metabolic syndrome 132
Decrease of proliferation and differentiation of
adipocytes 133
Promotion of lipogenesis 19
Loss of weight 134
Promotion of leptin release 102
Increment of β-oxidation and thermogenesis 97, 98, 109
Antidiabetic activity
Improvement of insulin response 8
Activation of the insulin signaling pathway 81
Antimicrobial activity 83, 104, 106, 135
Antiviral activity 84, 86, 87
Anti-osteoporosis activity 107
Anti-allergenic activity 10, 39
Antiestrogenic activity 10, 110
Photoprotective activity 93, 94
Anticariogenic activity 89
Prebiotic effect against Bifidobacterium 82, 136, 137
Neuroprotective effect 55, 12, 115, 128
Anxiolytic effect 50, 115