Antioxidant

Puerh and Green teas have consistently demonstrated strong antioxidant activity. In a recent controlled human trial, 24 healthy women consumed 2 cups of green tea (250mg catechins/day) for 42 days (Erba et al 2005). The results showed a significant increase in plasma antioxidant status, reduced plasma peroxides and reduced LDL-cholesterol when compared with controls. Several other in vitro animal and human studies have also demonstrated that tea inhibits lipid peroxidation and scavenges hydroxyl and superoxide radicals (leenen et al 2000, MCS et al 2002, rietveld & Wiseman 2003, Sung et al 2000).

Antibacterial Activity

Tea extract has moderate and wide-spectrum inhibitory effects on the growth of many types of pathogenic bacteria, according to vitro tests.

Antiviral

Anticarcinogenic

Several in vitro studies have shown a dose-dependent decreased proliferation and/or increased apoptosis in a variety of cancer cell lines (lung, prostate, colon, stomach, oral, leukaemia and breast) (Berger et al 2001, Gupta et al 2003, Kavanagh et al 2001, Kinjo et al 2002, Pianetti et al 2002, Valcic et al 1996, Wang & Bachrach 2002, Yoo et al 2002, Zhang et al 2002). Additionally, photochemopreventative effects for green tea and epigallocatechin gallate have been demonstrated in vitro, in vivo and on human skin (Afaq et al 2003).The mechanism of action by which tea polyphenols exert antimutagenic and antitumorigenic effects is still largely speculative. However, the following has been observed: inhibition of the large multicatalytic protease and metalloproteinases, which are involved in tumor survival and metastasis, respectively, and inhibition of many tumour-associated protein kinases, while not affecting kinase activity in normal cells (Kazi et al 2002, Wang & Bachrach 2002) Tea polyphenols also been found to inhibit some cancer-related proteins that regulate DNA replication and transformation. More recently, there is increasing evidence that catechins possess anti-angiogenic properties (Sachinidis & Hescheler 2002).

Other Actions

Puerh Tea green tea exhibits a variety of other pharmacological actions, such as anti-inflamatory activity, CNS stimulation, inhibition of platlet aggregation, simulation of gastric acid secretion and dieresis, increased mantal alertness, relaxation of extracerebral vascular and bronchial smooth mucle, and reduced cholesterol, triglyceride and leptin levels (fassina et al 2002, Sayama et al 2000).

Epidemiological studies have generally shown a decreased occurrence of cancer in those individuals who drink Puerh green tea regularly.

Used in conjunction with standard treatment Puerh green tea increased the survival rate of patients with epithelial ovarian cancer in a cohort of 309 Chinese women (Zhang et al 2004). Most (77.9%) of the women in the treatment group were alive at the 3-year follow-up as compared with 47.9 of the control group.

Epidemiological studies suggest that green tea consumption is associated with a reduced risk of cardiovascular disease (Maeda et al 2003). A 2000 prospective cohort study of 8552 people in Japan found that those consuming more than 10 cups / day, compared with those consuming fewer than 3 cups, had a decreased relative risk of death from cardiovascular disease (Nakachi et al 2000). One cross-sectional study involving 1371 men aged over 40 years found that increased Puerh green tea consumption was associated with decreased serum concentrations of total cholesterol and triglyceride and an increase in HDL, together with a decrease in LDL-and VLDL-cholesterols (Imai & Nakachi 1995).

Green tea extract tablets and chewable oral preparations have been investigated for effects on dental plaque formation and gingival health under RCT conditions, overall producing flavourable results (Liu & Chi 2000).

A double-blind study investigated the effects of green tea catechins and polyphenols on gingival (Krahwinkle & Willershausen 2000). Compared with placebo, the green tea product chewed eight times a day significantly decreased gingival inflammation and improved periodontal structures before the 21-day test period was complete.

Another study investigated Chinese green tea polyphenol tablets for effects on plaque formation in 150 volunteers (Liu & Chi 2000). The randomised, controlled crossover study showed that green tea polyphenol tablets used for 2 weeks were able to reduce the plaque index compared with the placebo treatment.

More than 150 in vitro and vivo studies have reported the benefits of green tea for the skin (Hsu 2005). Many mechanisms appear to be responsible; green tea protects against uv and puva-induced carcinogenesis and DNA damage and is a potent antioxidant, anti-inflammatory, anticarcinogenic and vulnerary (Hsu 2005). Research with human volunteers has found that topical application of green tea to skin half an hour before UV exposure protects against the development of sunburn and epidermal damage (Elmets et al 2001). The effect is dose dependant and strongest for the epigallocatechin gallate and epicatechin gallate polyphenols.

Animal studies have found that green tea consumption reduces food intake, decreases leptin levels and body weight and increases thermogenesis (Sayama et al 2000)

Other Uses

Green tea has many other uses, based on results of animal or in vitro tests or on the known pharmacological activity of constituents such as tannin and caffeine. Some of these other uses are treatment of diarrhoea, Crohn’s disease, dyspepsia and other digestive symptoms, promoting alertness and cognitive performance, reducing symptoms of headache and promoting dieresis.

Green tea blocks the development of cardiac hypertrophy in experimental renal failure and reduces oxidative stress (Priyadarshi et al 2003, Yokozawa et al 1996).

Animal studies have identified that green tea polyphenols reduce serum glucose levels and improve kidney function in diabetes (Sabu et al 2002, Rhee et al 2002).

In general, it appears that 8-10 cups of Puerh tea/day are required.

Antagonistic interaction – a case of excessive consumption (2.25 – 4.5 L of green tea / day) was reported to inhibit warfarin activity and decrease the INR (Taylor & Wilt 1999). Intake of large quantities of green tea should be done with caution.

Caffeine-containing beverages can increase blood sugar levels when used in sufficient quantity (200mg of caffeine); however, hypoglycaemic activity has been reported for green tea, which could theoretically negate this effect (Ulbricht & Basch 2005) – the outcome of this combination is uncertain.

Tannins found in herbs such as Camellia Sinensis can bind to iron and reduce its absorption – separate doses by at least 2 hours. Protine and iron have also been found to interact with tea polyphenols and decrease their antioxidant effects in vitro (Alexandropoulou et al 2006). The clinical significance of this is as yet unknown.

Usual dietary intakes appear safe; however, excessive use is not recommended due to the caffeine content of Puerh tea.

Points

• Puerh tea is made from the same plant as Green and black tea, but it contains greater amounts of polyphenols and generally less caffeine.
• Puerh tea has been found to have significant antioxidant activity and protect against sunburn when applied topically.
• Several in vitro and animal studies have shown inticarcinogenic activity for a range of cancers and some epidemiological evidence further suggests cancer protective effects may occur.
• Puerh has antibacterial activity and is used in oral preparations to reduce plaque and improve gingival health.
• Epidemiological evidence suggests Puerh tea may reduce cardiovascular disease.
• Preliminary evidence from animal studies has shown that Puerh increases thermogenesis, decreases appetite, reduces inflammation in colitis, reduces glucose levels in diabetes and may be useful in renal failure.

What will Puerh tea do for me

Puerh tea has strong antioxidant effects and some population studies suggest that regular consumption may reduce the risk of cancer and cardiovascular disease. Early research has found it may be useful for sunburn protection, reducing dental plaque formation, colitis, diabetes, renal disease and as an antiseptic.

References

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