The study involving 957 Chinese seniors aged 55 years or older over a period of several years found that regular consumption of tea decreases the risk of cognitive decline by 50%, while APOE e4 gene carriers who are at risk of Alzheimer’s disease may experience a reduction by as much as 86%.
APOE e4 is a gene that plays a critical role in redistributing lipids (naturally occurring molecules that include fats, waxes, sterols, vitamins and others) among central nervous system cells, repair injured neurons and maintaining neuron connections.
Image based on information from Dove Medical Press
Dr Feng Lei & his pioneering studies
The study was led by Assistant Professor Feng Lei from the Department of Psychological Medicine at the National University of Singapore (NUS). Dr Feng Lei’s primary research interest is in the epidemiology and prevention of cognitive decline and dementia in late life. He has over 90 research publications on ageing, psychiatric, and neuroscience research studies and is a regular peer reviewer for top journals such as the British Medical Journal.
Based on Dr Feng’s previous research, he said about 16% of Singapore’s population carries the APOE e4 gene. In another blog by Dr Brian Moore, a neuropathologist at the University of Colorado Anschutz Medical Campus, the prevalence of the gene is 20% of the population with European ancestry.
Image source: National University of Singapore
Dr Feng and his team also discovered that the neuroprotective role of tea is not specific to a particular type of tea leaves. As long as the tea is brewed from white, green, black or oolong leaves, the active compounds are present. These bioactive compounds are catechins, theaflavins, thearubigins and L-theanine. They exhibit anti-inflammatory and antioxidant potential, plus other bioactive properties that may protect the brain from vascular damage and neurodegeneration. However, the current understanding of the detailed biological mechanisms is still very limited so further research is required to find the definitive answers.
These research findings are published in The Journal of Nutrition, Health & Aging in December 2016. To find out more about his research, we tracked down Dr Feng at NUS, and he was gracious to take time out of his busy schedule to provide additional insights.
QUINTEA: Will diet/food affect the risk in getting dementia?
DR FENG: Yes. I am currently working on a project that focus on dietary factors and the risk of dementia. In this research, I will examine certain foods, beverages, dietary patterns, biological mechanisms, and interactions with APOE gene.
QUINTEA: The bioactive compounds: catechins, theaflavins, thearubigins and L-theanine – can these be found in other foods besides tea?
DR FENG: L-theanine can only be found in tea. Other compounds can be found from plants other than tea, but I think the amount is indeed very small, so tea is the most abundant source.
Dr Feng stress that he’s not a plant scientist so may not be the most cognisant regarding knowledge of plants.
QUINTEA: How do these bioactive compounds reduce the risk of dementia?
DR FENG: It is not clear but we have some good guesses based on current research data and biological plausibility.
Based on Dr. Feng’s article in the Journal of Prevention of Alzheimer’s Disease (AD), many molecular lesions have been detected in AD. The data supports the idea that an accumulation of these misfolded proteins in the aging brain results in oxidative and inflammatory damage, which leads to energy failure and dysfunction of neuron connection. Tea’s bioactive compounds protect the brain from AD with actions such as amyloid formation to reduce oxidative stress and inflammation.
Image source: www.dementiastatistics.org
QUINTEA: If drinking tea helps lower the risk of dementia, one would think countries with a long history of tea drinking like China and Japan will have lower cases of dementia. But according to Alzheimer’s Research UK, East Asia has the most people living with dementia (9.8m). Followed by Western Europe (7.5m), South Asia (5.1m), and North America (4.8m). Do you have any insights into the statistics and why East Asia has the highest number?
DR FENG: It is not so simple. Dementia is a multifactorial chronic condition.
Absolute number of cases is determined by the prevalence rate and the absolute number of older adults in the population, so counting the numbers is not meaningful. As for prevalence rate, there are many factors playing important roles. Tea is just one of many factors.
In my opinion, age itself is the most important risk factor, followed by cardio-metabolic conditions, depression, sedentary lifestyle etc. Education level is the most important protective factor, followed by active social engagement, regular participation in cognitive demanding activities etc.
QUINTEA: Since the article in Journal of Nutrition, Health & Aging in Dec 2016, do you have any new discovery into dementia?
DR FENG: I am working on the trends of cognitive impairment in China, for the period 2002 to 2014. The findings are expected to appear in scientific journal in 2018, if not 2019. I cannot tell you exactly what I found at this moment.
QUINTEA: Everyone grows old eventually. How do you personally reduce the risk of dementia.
DR FENG: I drink tea at least 5 days a week, 2 to 3 cups a day. I go swimming once or twice a week, brisk walking in the parks at weekend, and try to do some press-ups everyday in the evening. Plus I meet friends and participate in social and cultural activities regularly. As a scientist, I read, write and communicate with others everyday. All are considered as cognitive demanding activities: good for the brain.