The Effects of Theanine Consumption on Individuals with Alzheimer’s Disease

Alzheimer’s disease (AD) is a late-onset disease that usually occurs in individuals above the age of 65. Due to the advancements of modern health care people will now live longer, hence leading to an increase in the number of people with AD. Alzheimer’s disease continuously progresses with age leading to cognitive impairment and eventually death. It is currently the sixth leading cause of death, with no current prevention or treatment methods. Past research with theanine have provided some promise.

Theanine is a biomolecule mainly in tea producing plants. Past studies have supported that it can potentially be used as a prophylaxis or a treatment method for individuals with AD. It was found that over-stimulation of the NMDA receptor can lead to an increase of amyloid beta peptides in particular regions of the brain, which is characteristic of the disease. The increased activation of the receptor also caused a high toxic release of glutamate, which signaled for apoptosis of neuronal cells. Theanine has been shown to block the NMDA receptor, which ends up suppressing apoptosis and reducing the amount of amyloid beta peptides formed in AD.

In this paper I will be analyzing the study conducted by Kazuki et al. and how they used theanine as a treatment for patients with neurodegenerative diseases. The purpose for their study was to see the treatment effects that green tea extracts (theanine and catechins) had on elderly individuals with cognitive impairments. In order to obtain the appropriate sample Kazuki et al recruited 12 participants from a nursing home. Two of the participants were male and ten were male. This could have led to a confounding factor because women tend to have higher cases of AD in their older age.

The average age of the participants was 88 years old. Every participant had either early Alzheimer’s or another kind of neurodegenerative disease. There was also a set of inclusion and exclusion criteria. Some of the inclusion criteria were that the participants had to be over the age of 65 and had to be able to orally consume green tea extract in powdered form. The many inclusion and exclusion criteria cause the study to have less external validity. Therefore, becoming a weaker WSR model because the individuals that did not fit into the inclusion criteria will not be accounted for. One of the patients was taking prescribed dementia medication. This could have led to a confounding factor and provided weaker evidence in the EBM perspective. Participants consumed green tea powder for three months. A mini-mental state examination (MMSE) was given to the participants to assess the level of their cognitive impairments. The lower the score the higher their cognitive impairment. The examination had five components.

In addition, data was collected on the blood pressure, serum lipid levels and the blood glucose levels of the patients. This was done because Atherosclerosis has been shown to increase the likelihood of AD. Atherosclerosis is caused via high blood pressure. So, they checked to see if the extract would have any effect on lowering blood pressure. This process took more of a holistic approach because it was relating multiple diagnoses together. All the tests scores were taken at the beginning and after the three-month period. The total MMSE scores improved significantly by the end of the study.

The triglyceride levels in the participants’ blood had substantially decreased as well. Thus, the overall cognitive function had improved in the patients. In conclusion I do not think the data in this article provided enough evidence to support the suggested therapy for AD. The study could have been improved if it was double blinded. Both the patients and researchers were interacting with each other this could have lead to some bias. The powder did not only have theanine it also had catechins. Thus, the researchers will not be able to know which biomolecule was responsible for the alleged improvements in cognitive functioning. The sample size was also too small. Small sample sizes can skew the results. Also, the researchers that conducted the study are from the same company that provided the nursing home with grants and the powder to test on the patients. Thus, this may have led to a confounding factor and a weaker study in the EBM perspective. Lastly, the Study was not an RCT and only last a short period. Overall, using the EBM approach may have weakened this study.

References

1. Di X, Yan J, Zhao Y, Zhang J, Shi Z, Chang Y, Zhao B. l-theanine protects the APP (Swedish mutation) transgenic SH-SY5Y cell against glutamate-induced excitotoxicity via inhibition of the NMDA receptor pathway. Neuroscience. 2010;168(3):778–786. doi:10.1016/j.neuroscience.2010.04.019
2. Ide K, Yamada H, Takuma N, Park M, Wakamiya N, Nakase J, Ukawa Y, Sagesaka Y. Green Tea Consumption Affects Cognitive Dysfunction in the Elderly: A Pilot Study. Nutrients. 2014;6(10):4032–4042. doi:10.3390/nu6104032
3. Vuong QV, Bowyer MC, Roach PD. L-Theanine: properties, synthesis and isolation from tea. Journal of the Science of Food and Agriculture. 2011;91(11):1931–1939. doi:10.1002/jsfa.4373