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Electroencephalographical investigation of drinking green tea to the human brain

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INTRODUCTION
The brain is the largest electricity generator in the body. Brain electricity can be defined as brainwaves. The variety of brainwaves is influenced by neurotransmitters-neurochemical that affects neuron function-that could affect health promotion in various aspects. Four types of brainwaves have to be recognized, Beta, Alpha, Theta and delta. 1 Each type of brainwave could be affected by nutrients or substances from foods or beverages. 2 This effect could promote regeneration or degeneration of total health benefits.
Tea has broad health benefits from green tea to black tea due to its plant chemicals. Catechin is the main compound which is found in green tea whereas Theaflavin is mainly found in black tea. Not only theaflavin is found in black tea but thearubigins, Theobromine, Theophylline, Theanine and caffeine also. 3,4 Tea, Camilliasinensis, is one of the most popular beverages consumed in the world. There are many types of tea which differentiate by fermentation process. Approximately three billion kilogrammes of tea is produced and consumed yearly. Many kinds of tea are consumed in different parts of the world. Green tea, which is 20% of consumption, is favored in Japan and China. 78% of tea consumption is black tea, which is consumed in Western countries and 2% is Oolong tea which is produced (partially fermented) mainly in southern China. 3 Nowadays green tea has become one of the most popular drinks all over the world. Evidences suggest that green tea become second most consumer following regular drinking water. Green tea contains Theanine, an amino acid primarily found in green tea and black tea. The content is generally found 1-2% of dried tea or around 60 milligrams per 200 milliliters of tea drink. In particular, this substance is found in the form of L-theanine that can be absorbed to the blood system and then to the brain within 30 minutes, which L-theanine that relaxation and reducing stress.These kinds of components make various benefits for health such as antioxidant, anticancer, antiatherosclerosis effect, moreover, brain health promotion such as Alzheimer's disease, Parkinson even increase attention. 5,6 A review by Ruxton summarized 23 studies on the impact of caffeine on cognitive function finding positive effects on mood, alertness, mental performance at acute intake 37.5 -450 mg. 6 Electroencephalography (EEG) is traditionally used to measure the brainwaves. Each type of brainwave is associated with one's state of consciousness and different mood state. From all types of brainwave, beta brainwave was seen in normal activities as well as stressful conditions or difficulties in mental concentration. 7-10 On the other hand, alpha brainwave is seen in wakefulness, relaxed, effortless and alertness condition. Therefore, persons with high alpha brainwave and low in beta brainwave could indicate status of relaxation, arousal, less stress and better concentration. [11][12][13][14][15] In the present study, the measurement of brainwaves of accumulative drinking of green tea were done by the effectiveness of commercially available electroencephalographic (EEG) device, eego TM mylab. The benefit of this study was to provide the guideline for planning and campaigning green tea consumption for the purpose of stress reduction resulting in relaxation.

Participants
The experiment was conducted with twelve volunteers aged between 21-55 years. All healthy participants were with no underlying disease, no history of brain surgery, no congenital illness, and not taking medicines or drugs that affect to nervous system. The protocol of this study was approved by the Ethical Committee of Mae Fah Luang University, Thailand.

Tools and equipment
Recording personal information, namely, age, gender, nationality and history of illness were recorded. The electroencephalography (EEG) was applied in this study. The neuroheadset was used to display the output, analyze and record EEG power spectrum. In this study, the effectiveness of commercially available electroencephalographic (EEG) device, eego TM mylab (ANT Neuro, Hengelo, Natherlands), was applied. The eego TM mylab is ideal for investigating all kinds of EEG paradigms. The eego TM mylab comes in four variants for recordings from 32 to 256 EEG channels. The number of channels can be easily increased by adding additional 64-channel amplifiers to the setup. Additionally, each of the 4 variants can be easily extended for simultaneous recordings with of up to 24 EMG channels or to a combination of EMG channels with a variety of physiological sensors from both the brain and body (Figure 1).

Statistical analysis
Analyzed the basic demographic data of participants by using descriptive analysis with qualitative data summarize in term of frequency and percentage, with quantitative data summarized in term of average and standard deviation. Use inferential statistic compared each type of EEG power spectra of before and after experiment by compared t-test while performing the accumulative drinking of green tea. Every test was set to the statistic significant at p<0.05.

RESULTS
Based on Table 1 Figure 2, it was found that delta and theta brainwaves gradually declined while alpha, beta and gamma  However, it was found that beta brainwave was not changed after accumulative drinking of green tea (before drinking: 0.11±1.87µV; after drinking: 0.34±0.27 µV; t(11) = 1.37; p=0.91) the same as gamma brainwave which was also not changed after accumulative drinking of green tea (before drinking: 0.34±0.18µV; after drinking: 0.52±0.67µV; t(11) = 0.73; p=0.14).

DISCUSSION
The aim of the current study was to find out whether there was an influence of green tea on brainwave and attentive process in a accumulative drinking period. In the current study, the influence to brainwave and attentive process were tested by experimental design. The study indicated alpha brainwave was shown after drinking green tea. Interestingly, frequency of alpha brainwave along accumulative drinking of green tea was shown significantly since the 10 th minute; however, spectrum of the alpha brainwave changed significantly after drinking green tea, after 30 th minutes. The influence of green tea in this study to attention associated with a study of Bruin that black tea improved reaction times on the sensory-attention test, 16 nevertheless, not associated with Bruin's study in accuracy. Accordingly, alpha brainwave was still associated with alertness and peacefulness 17,18 and corresponded to memory storage and processing. 1 Alpha brainwave in current study was dominantly shown on Fz position where associated with working memory and also attention, according to Broadmann cortical area. 19 This effect of alpha brainwave could be associated with attention on doing spatial test together ingredients from Theanin, 16 which is known to help attention and increase alpha wave activity according to a study of Gomez-Ramirez and Owen. 20 Alpha brainwave has shown on Fz position, though, it is also shown on Cz position which corresponded to somato association cortex, according to Broadmann cortical area. 19 This position related to working memory from visual and visuomotor attention. 19 Spectrums of alpha brainwave from this position were associated with doing visual spatial test of participants.
Interestingly, caffeine is known to inhibit neurotransmitters that slow down brain activity and influence others that alter mental performance such as noradrenaline, dopamine and serotonin as the study from Fredhlom. 6 All this information was the reason for this study to study brainwaves and attentive processes in accumulative drinking of green tea in order to promote longevity and health. This study had been set to prove the hypothesis that brainwaves could be changed after cumulative drinking green tea.

CONCLUSION
It was found that the means of the alpha brainwave of the samples were increased. The accumulative drinking of green tea in this study might affected to the samples nervous systems including the central and automatic nervous systems. This way of accumulative drinking influenced the central nervous system by making the samples significantly felt happy and relaxed. The accumulative drinking of green tea could help promote alpha brainwave which help relaxing and attention. This could promote longevity for brain health in the term of improving attention with no stress.

ACKNOWLEDGEMENT
This research was supported by research funding from Mae Fah Luang University grant (Electroencephalogram