Parkinson’s disease is the second commonest neurodegenerative disease after Alzheimer’s, affecting 1% of the over-65 population and 2% of the over-80’s. Recent research (1) published in Biological Psychiatry from the Institute of Biophysics, Academia Sinica in Beijing indicates that polyphenols in green tea have a protective effect on neurons that could be put to potential clinical use.

In a laboratory study carried out on rats, serving as the animal model for Parkinson’s disease, damage was inflicted upon dopamine-secreting neurons of rats — simulating the disease in humans where the loss of such neurons leads to debilitating disorders of movement. Controls were set up by dividing the rats in 6 groups - control group not receiving neurotoxin, control group receiving normal diet plus neurotoxin, two study groups receiving neurotoxin and 150 mg/kg and 450 mg/kg of green tea polyphenols respectively, and two control groups receiving polyphenols only in the above doses.

The results showed significant neuroprotective effects of green tea which depended on the dose being administered - overall 3.7 times more neurons survived in the combined group that received polyphenols with neurotoxins, than those who received neurotoxins alone. Dr Baolu Zhao (senior author) and his colleagues also links this protective effect of polyphenols to inhibition of the ROS-NO pathway which is thought to mediate cell death in Parkinson’s disease. This pathway is thought to generate nitric oxide and free oxygen radicals, both of which are lethal to neurons. Free radicals are also thought to be related to a number of diseases and even aging, and this anti-oxidant function of green tea has been traditionally explained as the reason behind green tea’s reputation as an anti-aging agent.

However, it must be remembered the study does not imply that drinking copious amounts of green tea will protect against or cure Parkinson’s disease. Laboratory conclusions often do not hold out in clinical trials, and health claims for well known agents like Ginko Biloba and St. John’s Wort have not held out in carefully controlled clinical studies. Moreover, large prevalence studies (2) have not shown any difference in prevalence rates of Parkinson’s disease between China, where green tea drinking is common, and the Western world.

However, this study does indicate that drugs developed from polyphenols do merit clinical trials in the near future as possible anti-Parkinson’s agent. Another triumph of the potential of alternative medicine, perhaps.

References

(1) Shuhong Guoa, Jingqi Yana, b, Tangbin Yangd, Xianqiang Yange, Erwan Bezardc and Baolu Zhao. (2007) Protective Effects of Green Tea Polyphenols in the 6-OHDA Rat Model of Parkinson’s Disease Through Inhibition of ROS-NO Pathway. Biological Psychiatry. Volume 62, Issue 12, 15 December 2007, Pages 1353-1362.

(2) Zhen-Xin Zhang, Gustavo C R et al. (2005) Parkinson’s disease in China: prevalence in Beijing, Xian, and Shanghai. The Lancet 2005; 365:595-597.

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