Green Tea the Benefits of Health Over the past 15–20 years, a number of other research studies have been conducted to determine what health benefits can be attributed to consumption of green tea and its extracts. This research has shown that green tea has a variety of potential health benefits. These benefits include anticarcinogenic, anti-inflammatory, antimicrobial, and antioxidant properties, and benefits in cardiovascular disease and oral health. While much of this research has been performed in vitro, and a significant amount of the research done in vivo, using animal models, this will focus mainly on studies conducted with human subjects plus pertinent information from the other types of studies. Anticarcinogenic Properties of Green Tea Cancer is currently a major source of morbidity and mortality worldwide. Billions of dollars in research monies have been poured into cancer research over the past 50 plus years, and yet we do not seem to be any c
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Green Tea the Benefits of Health
Over the past 15–20 years, a number of other
research studies have been conducted to determine what health benefits can be
attributed to consumption of green tea and its extracts. This research has
shown that green tea has a variety of potential health benefits. These benefits
include anticarcinogenic, anti-inflammatory, antimicrobial, and antioxidant
properties, and benefits in cardiovascular disease and oral health.
While much of this research has been performed
in vitro, and a significant amount of the research done in vivo, using animal
models, this will focus mainly on studies conducted with human subjects plus
pertinent information from the other types of studies.
Anticarcinogenic Properties of Green Tea
Cancer is currently a major source of morbidity
and mortality worldwide. Billions of dollars in research monies have been
poured into cancer research over the past 50 plus years, and yet we do not seem
to be any closer to actually curing it. In addition, quite often the
chemotherapies do as much, if not more damage to the patient as the disease.
Because cancer appears in so many different
forms in multiple parts of the body, it has been difficult to determine the
mechanisms that lead to the disease. Even with what we now know about cancer risk
factors, there are still many people who seemingly have none of the risk
factors, and yet succumb to a rapidly aggressive form. Encouraging people to
think about how a healthy lifestyle can prevent disease is certainly a step in
the right direction, and it would be most helpful to identify substances that
could be useful in prevention and treatment.
The main component of green tea that has been
studied in cancer research is EGCG. There are several cancer related mechanisms
attributed to EGCG. These include: inhibition of angiogenesis, DNA
hypermethylation, NF- B, telomerase activity, and tumor cell proliferation and
metastasis; induction of tumor suppressor genes; and promotion of tumor cell
apoptosis.
Inhibition of angiogenesis is suggested to occur
through a decrease in RNA and peptide levels of vascular endothelial growth
factor (VEGF), and by disrupting the dimerization of VEGF with the vascular
endothelial growth factor receptor. Another suggested way in which green tea
catechins may generally inhibit carcinogenesis is through increasing levels of
glutathione S-transferase pi (GST-pi), which catalyzes detoxification reactions
that inhibit carcinogen-induced DNA damage.
Analysis of studies performed using human oral
consumption of green tea to assess cancer risk showed that case-control studies
gave the most consistent results and was positive for reduced cancer risk in
breast, cardiac, colorectal, esophageal, gastric, lung, ovarian, pancreatic,
and prostate cancers. A recent large study showed a relationship between breast
cancer risk and tea consumption, with the risk being highest in the groups that
did not consume tea and lowest in the groups that consumed the most cups per
day.
Number of cups were assessed in five categories
(0.1–1.0 cups, 1.1–2.0 cups, 2.1–3.0 cups, 3.1–5.0 cups, >5.0 cups).
Analysis of the types of green tea beverage or extracts used in studies
suggests that green tea beverage or a supplement containing mixed catechins may
be more effective than using single catechin (e.g., EGCG) supplements.
The potential molecular mechanisms and targets
that might explain how green tea catechins possess anticarcinogenic properties
have been widely studied (using various cell cultures, etc.),especially
in breast cancers. These include interaction with specific proteins,
anti-angiogenesis mechanisms, targets for inhibition of enzyme activities and
cell signaling pathways, and induction of cell cycle arrest and apoptosis.
The mushrooming area of nanotechnology has lead
to the development of potential chemotherapy involving nanoparticles (NPs).
Various particles (e.g., gold) can be used to deliver compounds to specific
areas of the body. Research using EGCG and nanoparticles has already begun
using a number of delivery approaches.
These include: coating an NP, such as gold, with
EGCG; use of encapsulated (in liposomes or polymeric NPs) EGCG in NPs along
with anti-cancer drugs, outer ligands that will bind to specific targets, or
outer polymers that will enhance the intestinal absorption of EGCG.
Cardiovascular Disease Health Benefits
Cardiovascular disease (CVD) is a complex
disorder involving multiple factors. Among those factors are inflammation,
oxidative stress, platelet aggregation, and lipid metabolism. Some of these
factors are also involved in other disease processes, but will be discussed in this
paper under CVD.
There have been a number of studies over the
years assessing green tea consumption in respect to CVD risk. Two studies from
Japan that included nearly 50,000 people found a decreased mortality rate due
to CVD based on consumption of various numbers of cups per day. One study
showed a 28% decrease in CVD death between those who consumed 3 cups and those
who consumed 10 cups.
The other study showed a 14% decrease in CVD
mortality between those who consumed <1 cup and those who consumed 5 cups.
Other studies in Japan using a green tea extract found that, after 12 weeks,
the subjects had reductions in body fat (10%), blood pressure (6.5%), and
low-density lipoprotein (LDL) levels (2.6%), suggesting reduced risk of CVD.
After two months, diabetic patients also had
reduced fasting blood glucose levels (from 135 to 128.8 mg/dL), and hemoglobin
A1c (HBA1c) levels (from 6.2% to 6.0%). A large meta-analysis of 17 studies
from over 30 years, including data from Europe, the UK, and the U.S., found
that increasing consumption of green tea by three cups per day decreased the
risk of myocardial infarction (MI) death by 11%.
Another study showed a decreased risk of
mortality in patients who had an acute MI and a history of regular green tea
consumption for at least a year prior to the MI. Participants who did not drink
green tea had a 14% rate of death due to the MI; participants who drank up to
14 cups per week had an 11% rate of MI death; and participants who drank more
than 14 cups per week had a 10% rate of MI death.
An interesting study in patients with CVD showed
that consumption of EGCG resulted in a rapid improvement of vascular
endothelial function. Participants who ingested an initial dose of 300 mg of
EGCG had an improved brachial artery flow-mediated dilation from 7.1% to 8.6%
after 2 h. Another recent study found that increased intake of dietary
flavonoids was associated with a decreased risk of CVD.
The participants were divided into three groups
based on average daily consumption of flavonoids. The first tertile consumed 89
mg/day, the second tertile consumed 251 mg/day, and the third tertile consumed
532 mg/day. The number of deaths due to CVD in the first tertile was 8.6%; in
the second tertile, 6.4%; and in the third tertile, 5.0%.
Inflammation
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Besides CVD, inflammation is also involved in
arthritis, aging, cancer, etc. Many of the anti-inflammatory effects when using
green tea have been studied in rheumatoid arthritis (RA) and osteoarthritis (OA),
and are pertinent to CVD as well. Some general anti-inflammatory mechanisms of
green tea components are:
increased production of the anti-inflammatory
cytokine, IL-10; regulation of IL-6 synthesis and signaling; decreased
production of destructive matrix metalloproteinase’s via TNF-induced
phosphorylation of mitogen-activated protein kinases (MAPKs); and decreased
expression of the chemokine receptor CCR2 and decreased levels of the
proinflammatory cytokines IL-1 and TNF-.
The specific studies on inflammation can be
roughly categorized into: inhibition of neutrophil-endothelium interaction,
modulation of neutrophil functions and death, and regulation of inflammation
factors. Neutrophil migration and function is an integral part of the inflammatory
response, so controlling neutrophils is vital in decreasing inflammation.
Studies have shown that green tea catechins
cause a reduction in the number of leukocyte-endothelial cell adhesion
molecules (CAMs), such as ICAM-1, VCAM-1, and E-selection, expressed on the
endothelial cell surface. This restricts the ability of the neutrophils to
migrate to sites of infection.
Other studies have shown that factors known to
regulate neutrophil function. such as IL-1 , IL-2, TNF- , and
granulocyte-macrophage colony-stimulating factor (GM-CSF), are suppressed by
consumption of green tea or EGCG, resulting in inhibition of inflammation.
Studies on the inhibition of pro-inflammatory factors have shown that green tea
catechins downregulate many inflammatory.
Oxidative Stress
![Oxidative Stress Oxidative Stress](https://1.bp.blogspot.com/-nISYDunXGwI/Xmkjb3ES5oI/AAAAAAAACTs/qlhaZwEVIrw1Y-3akwuUgEFAST0BOdvfQCEwYBhgLKskDAMBZVoCO_ZYQ_uRPPvzoKiYbJqlw3VDPntPshpM8ECQPtdq_9t6UyEK4whJ-UMdxIWl-cde9PRgrVYP_XCye4GM5Glb-DLBevMcEadxBGDO71mVCXFVINhD2yOwnZShq3I8WdaJ7K0yW8GXVYSpDNKoQrvUeKAk9JTCl6m5sQNoNThZIugbpOCS_3PSy_Ge8h8a8udrRk_yGIfcEkdKzohYZV9fqGcbRP00elODV7cab2MNQhnzf4889Ewz_3ioPwpBArsgvklZgzJeRx78Isab8mxcSEPqSiXcxE2GX1SzIHcc3Tw2g2PMbt1hF_FNd_RhN7kdiM_TQ2YYAyRCp2BNqjcAeHsXwsNGkxNK8REL2kj_k6tXQl9fhQWFh2DYVGWdSy81DDgXMxvZHA7tDNtCzW6JGopFAYYKLduSeJ3Dx_clOeMqZZTpdBNaUzRPBuniGSUosYTZTDlv9WYCigopVptpDHC_HEhdqfxwrMMKZg6ebQpc1ay4aIHl_RxTYWXqIozldus_NWn6V5hJPhU7qPI0bHKX61ZOOxWfMcnk70hkgVinRjb4kycg2SoO0kyUxVbswmHCChWLrxwGCOPIAtLsHHLDbYTDYyqTzBQ/s640/12-3-20-5.jpg)
Oxidative stress in the body is closely tied to
inflammation and CVD, and is the result of the damaging effects of reactive
oxygen species (ROS). These ROS are capable of causing chronic inflammation
through induction of inflammatory cytokines and chemokines, and
pro-inflammatory transcription factors.
In general, green tea catechins have been found
to have antioxidant activity through: inhibiting redox sensitive transcription
factors and pro-oxidant enzymes, scavenging ROS, and inducing anti-oxidant enzymes.
Studies to determine the antioxidant capabilities of green tea may measure a
variety of substances.
Tests may measure the presence of known ROS or
their metabolites, such as hydroxyl radical, peroxides, superoxide, and singlet
oxygen. Other measurements may be for known antioxidant substances such as
superoxide dismutase (SOD) and glutathione peroxidase, or substances that
indicate inflammation such as high-sensitivity C-reactive protein (hs-CRP) and
TNF.
Another type of testing assesses total
antioxidant capacity (TAC), also known as total antioxidant status (TAS), which
measures the amount of oxidants that are neutralized in the body (e.g., moles
of oxidant neutralized by 1 L of plasma), with a lower number translating into
a higher risk of disease .
The results from recent studies have shown that
green tea catechins can affect levels of ROS , increase levels of antioxidants , decrease levels of inflammatory substances ,
and increase TAC (TAS). An excellent summary of earlier studies that measured
ROS and TAC can be found in a chapter by Serafini et al. 2011.
Platelet Aggregation
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Platelet activation and subsequent aggregation
play an important role in CVD. When the vascular endothelium is damaged,
platelets usually respond rapidly and aggregate to form plugs at the damage
site, and may also form clots that could lead to vessel occlusion. Many of the
studies on platelet aggregation have been carried out using various animal
platelets.
In addition to showing that green tea catechins
were involved in inhibition of platelet aggregation, studies suggested that
catechins may affect several cellular targets that are related to platelet
activation, including: through the arachadonic acid pathway, inhibition of a
cytoplasmic increase in calcium, decreased thrombaxane A2 (TXA2)
production, and inhibition of cyclooxygenase-1 (COX)-1.
A study using human platelets concluded that
EGCG was able to inhibit platelet activation by adenosine diphosphate (ADP)
stimulation, and suppressed the p38 MAPK phosphorylation of heat shock protein
27 (HSP27), which would inhibit the release of pro-thrombotic contents from
platelets.
Lipid Metabolism
Increased blood lipid levels have long been
suspected as an increased risk for CVD, especially LDLs. One mechanism that is
linked with atherosclerosis is the presence of oxidated LDL . There have been
many studies performed using humans subjects to determine the effect of green
tea catechins on lipids. The studies have reported that consumption of green
tea catechins lowers total cholesterol and LDL levels and also reduces blood
pressure.
In addition, a recent study found that green tea
catechins are incorporated into LDL particles, and are then able to reduce the
oxidation of LDL. Catechins prevent LDL oxidation via radical-trapping
abilities and act as hydrogen donors to -tocopherol radicals.
Oral Health Benefits
![Oral Health Benefits Oral Health Benefits](https://1.bp.blogspot.com/-Vdxq1VD7BiU/XmkjZ84htMI/AAAAAAAACTw/KbqAd5h2YrsCQKdMsxggiuBPu_YEEqhjACEwYBhgLMMLLpPMF/s640/12-3-20-11.png)
During the course of the many research studies
done using green tea catechin consumption, it was noticed that the research
subjects seemed to have improved oral health after consumption. Research was
then launched to focus on the effects of green tea on oral health.
Two of the general ways in which green tea
consumption helps oral health are due to its anti-inflammatory properties, and
antimicrobial activity against mouth flora such as Streptococcus mutans . The
antimicrobial activity may also be responsible for the improvement observed as
to bad breath the two major types of effects on oral health are a decrease in
periodontist and dental caries.
Periodontitis
Green tea consumption has been found to result
in decreased tooth loss, and prevent the development and progression of
periodontitis. Green tea consumption also has positive effects on periodontal
health when assessed as to probing depth, attachment loss, gingival bleeding,
and dentin erosion.
In addition to the antimicrobial effects on the
main bacteria involved in gingivitis, Porphyromonas gingival is, EGCG has been
shown to inhibit the ability of the bacteria to bind to oral epithelial cells
via fimbriae, and has also been shown to inactivate bacterial collagenases.
EGCG also inhibits production of matrix metalloproteins and IL-8, which are
responsible for initiating tissue destruction.
Dental Caries
![Dental Caries Dental Caries](https://1.bp.blogspot.com/-8pNCdP8ANHI/XmkjanWuKnI/AAAAAAAACTw/uNImzYmEDnsKWWHbD0bJzIyWER-ZKK9fACEwYBhgLMOPLpPMF/s640/12-3-20-12.jpg)
Prevention of dental caries is attributed to the
ability of EGCG to bind and inhibit salivary and bacterial amylases, in
particular, -amylase. EGCG also prevents generation of acid from carbohydrates
through inhibiting the transcription and function of LDH.
One of the main things that encourages tooth
decay is that the major oral bacteria (e.g., Streptococcus mutans) form a
biofilm on the surface of teeth. EGCG inhibits the adherence of the bacteria to
teeth, decreases biofilm formation, and inhibits the ability of the bacteria to
produce an acid environment. EGCG also inhibits the hydrogen binding and
hydrophobic interactions of bacterial collagenases. Consumption of green tea
has also been associated with an increase in oral peroxidase activity.
Conclusions
Green tea catechins have proved to be very
versatile in providing health benefits. This means that there are potential
health benefits for everyone in the consumption of green tea. Even moderate
amounts of consumption (drinking 1–2 cups of tea per day) may have benefits. It
is a very good thing that it is the second most popular beverage worldwide, as
the differences in health in a world without green tea might be significant.
There is fortunately a wide variety of research
being performed using green tea catechins, and we are starting to see many
studies performed using human subjects, as it is extremely important that we
are able to show the direct benefits to humans. The expansive repertoire of
green tea activity in health is important, especially to those people who live
where medical assistance is not generally available or affordable.
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