Green Tea and Neurodegenerative Diseases
By Justin H. Joe, Ph.D. & H. S. Jeon, Ph.D.
‘With the prolonging of the lifespan in humans, many age-related diseases are becoming more of a problem. While there have been numerous studies on neurodegenerative diseases, studies on the effects of green tea on neurodegenerative diseases have only fairly recently been undertaken. Current research shows that because green tea has natural and potent anti-oxidative properties, drinking green tea regularly can have neuro-protective effects .
Neurodegenerative diseases are disorders that affect the neurons in the brain. These diseases are not curable and progressively get worse as the nerve cells degenerate or die over time. This can cause huge problems in mental functioning . This loss of mental function/ cognitive function and behavioral abilities is called dementia . Commonly known diseases that fall under dementia include Alzheimers disease, Parkinson’s disease, and vascular dementia. Alzheimer’s disease and vascular dementia are considered primary types/causes of dementia. Alzheimer’s disease can also be considered a vascular disorder (disorder involving the interruption of blood flow to the brain) .
Furthermore, before an individual is diagnosed with a full blown dementia, there can be a transitional state between cognitive decline due to normal aging and mild neurodegenerative diseases. This is called MCI or mild cognitive impairment. It is characterized by deficits in memory performance despite normal cognitive function SMCs or subjective memory complaints are indicative of cognition related mental problems and are acknowledged as initial criteria of mild cognitive impairments. In other words, subjective memory complaints are important in the diagnosis of mild cognitive impairments. The early diagnosis and treatment of subjective memory complaints is important because individuals with subjective memory complaints are considered to be at higher risk for dementia .
A major characterization of the neuropathy of aging and neurodegenerative diseases is oxidative stress. Oxidative stress is a condition of cellular pro-oxidant-antioxidant disturbance that favors the pro-oxidant state . Oxidative stress plays an important role in the development of many neurodegenerative diseases and plays a large role in the cognitive decline in the early stages of these diseases .
Green tea itself has very potent anti-oxidative properties. Flavonoids are natural antioxidant substances present in dietary sources such as fruits and vegetables, and from plant derived drinks such as pomegranate, raspberry, and blueberry juice, red wine, and tea. The largest group of flavonoids present in green tea is that of natural antioxidant polyphenolic catechins. The major green tea catechins include EC, EGC, ECG, and EGCG. All four green tea catechins have been shown to be powerful antioxidants, EGCG being the most active of the green tea catechins. Green tea catechins can protect and rescue brain neurons against many types of exogenous damage; and it can modulate several signal transduction pathways, cell survival/ death genes, and mitochondrial function. All this contributes to the normal growth and development of neurons .
Another benefit of green tea is that it can improve cognitive ability in individuals at risk for dementia. A study published in 2011 demonstrates that LGNC-07, an ingredient that contains both green tea extract and L-Theanine, improves memory and attention in individuals with mild cognitive impairment. This study took 91 individuals with mild cognitive impairments who scored between 21 and 26 on the MMSE-K, and divided them into a treatment group (45 individuals took a total of 1,680mg of LGNC-07) and a placebo group (46 individuals were given maltodextrin and lactose for 16 weeks). The MMSE-K is a neuropsychological test that is designed to measure various cognitive functions such as memory, orientation, language, attention, and concentration. The test is used to assess patients with moderate to severe Alzheimer’s disease. The results of this study showed that LGNC-07 improves cognitive function (increased memory and attention) in individuals with mild cognitive impairment whose MMSE-K score was between 21 and 23. Through the use of an EEG, it was also found that LGNC-07 increased theta activity during active mental states .
Finally, an animal study on rats shows that green tea polyphenols improved cognitive deficits caused by chronic cerebral hypoperfusion (similar to vascular cognitive impairment in people). The study used 10-week-old Wistar rats and surgery was performed on these rats to induce hypoperfusion. For the next 4-8 weeks, the rats were fed either a saline treatment or different dosages of green tea polyphenols. Results of the study showed that the rats given 400 mg/kg per day had better spatial learning and memory than the rats given the saline treatment. Through this study, it is seen that green tea polyphenols scavenge free radicals, enhance antioxidant capabilities, and reduce lipid peroxidation and oxidative DNA damage after chronic cerebral hypoperfusion, which may underlie cognitive function improvement .
In conclusion, although green tea cannot outright cure and stop the symptoms of neurodegenerative diseases, there is much hope in using green tea as treatment for the prevention of such diseases and to perhaps slow down their progression. Regular consumption of green tea over long periods of time has numerous benefits that may aid neurodegenerative diseases such as combating oxidative stress, improving memory and cognition in individuals with MCI, and potentially improving spatial learning and memory in individuals with vascular dementia.
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