Keep those ‘grey cells’ ticking with a cuppa
Ahumble ‘kahata’ a day could very well keep dementia at bay.
This was the powerful message by Consultant Psychiatrist Prof. Shehan Williams that reverberated at the Lanka Alzheimer’s Foundation in Colombo 10 recently, as he confessed that after studying the goodness of tea he, a coffee lover, is now entranced by tea.
As an overcast day ended in a gloomy rain-lashed evening, this Professor in Psychiatry at the Faculty of Medicine, University of Kelaniya, began his talk on ‘Tea & Cognition: More than a storm in a tea-cup’ with a picture of a temptingly steaming cup of tea, soon after depicting lovely vistas of green-carpeted tea lands.
These tea lands have been part of Sri Lanka’s heritage for more than 150 years since a reclusive Scotsman, James Taylor wanted to see what would happen if he left two leaves and a bud of a certain new plant to wither on the verandah of his bungalow on the coffee-estate of Loolecondera in Galaha, after being badly-hit by the coffee blight.
Prof. Shehan Williams. Pix by Priyantha Wickramaarachchi
The rest, of course, is history, but this cuppa that Sri Lankans have been gulping down and from which the country earns much foreign exchange has ‘revealed’ certain qualities which could very well place it as the elixir for brain health.
“Tea is a safe, low-cost ‘drink’ available aplenty which is useful in preventing cognitive decline,” underscores Prof. Williams who is a leading researcher on Alzheimer’s disease in Sri Lanka and has this July published a review article on ‘Diabetes and Alzheimer’s Disease: Can Tea Phytochemicals Play a Role in Prevention?’in the International Journal of Alzheimer’s Disease with a group of eminent researchers at Edith Cowan University, Perth, Australia.
“The underlying mechanisms are not completely understood and we don’t know how much tea needs to be consumed, but there is a clear pointer at the neuroprotective effects of tea,” he said.
Before taking a deep look into a tea cup, Prof. Williams explains that tea is the dried tea powder/leaves produced from the leaves of the plant with the scientific name, Camellia sinensis.
Depending on the
method of processing, three varieties of tea
are produced:
- Black tea – This is fully processed tea under which the leaves are subjected to withering, rolling and fermentation followed by firing. It is also fully fermented tea and 78% of the tea-drinkers of the world consume this.
- Oolong tea — This is partially-fermented tea, taken by less than 2% of tea-drinkers.
- Green tea – Minimally processed non-fermented tea where the leaves are heated immediately after harvesting through a process of steaming, to prevent oxidation, followed by rolling and drying of the leaves. Green tea is consumed by 20% of the tea-drinkers.
Reiterating that it does not seem to matter what type of tea one drinks, Prof. Williams goes on to breakdown the ‘goodness’ of tea into its composites:
There are:
- 15-20% proteins
- 1-4% amino acids: Theanine (or 5-N-ethyl-glutamine), glutamic acid, glycine, serine, aspartic acid, tyrosine, valine, leucine, threonine, arginine and lysine. Theanine is a unique amino-acid exclusively present in tea and accounts for 50% of the total amino acids.
- 5-7% carbohydrates: Pectins, glucose, fructose, cellulose and sucrose.
- 5% minerals and trace elements including potassium, manganese and fluoride ions.
- Trace amounts of lipids, including essential fatty acids (linoleic and a-linolenic acids) and stigmasterol.
- Vitamin B, C and E
- Xanthic bases: Caffeine and theophylline
- Pigments: Chlorophyll and carotenoids
- Volatile compounds including aldehydes, alcohols, esters, lactones and hydrocarbons
Pointing out that tea is “rich” in phytochemicals (biologically active compounds found in plants), he says there are polyphenols, mainly flavonols known as catechins and epicatechins, that bring about the main health benefits. Catechins are present in higher quantities in green tea (20-80 mg/g) than in black tea (5-30 mg/g), due to the differences in the processing conditions of the tea leaves.
Before putting into a nutshell some of the enlightening studies conducted on tea across the world, Prof. Williams says that tea is believed to give both direct and indirect benefits to drinkers. While the direct involves neuro-stimulation and protection, the indirect is linked to anti-obesity, lowering of lipids and prevention of diabetes, hypertension, stroke and Alzheimer’s disease.
- Direct neuroprotection brought about by anti-oxidants – In-vitro (outside a living organism) work using different techniques such as cell culture and enhanced chemiluminescence exhibits that green and black tea extracts have considerable antioxidant activities due to the presence of catechins, theaovins and thearubigins.
There was a significant increase of plasma antioxidants after a single dose of either black or green tea, with green tea being six-fold more potent than black tea.
Referring to what happens when milk is added to tea, he points out that in-vitro studies reported a decrease in the quantity of plasma antioxidants, but in-vivo (within a living organism) work led by other researchers show that the bioavailability of phytochemicals of green and black tea was not impaired by the addition of milk.
- Direct effect on cognition — Caffeine and L-theanine in tea improved cognition, enhanced speed and accuracy of attention-related performances, increased mental clarity and alertness and improved mood as well as work performance compared to caffeine alone.
Quoting two double-blind, randomized, placebo-controlled human clinical trials which studied the effect on attention using attention tests (the switch task and the intersensory-attention test), Dr. Williams says that they reported that black tea could significantly enhance accuracy on the switch task and self-reported alertness.
- Anti-obesity and lipid-lowering factors — Theaflavins prevent fatty liver and obesity by reducing the total lipid, triglyceride and cholesterol levels in fatty acid (FA)-overloaded liver cell lines.
A study with rats showed a reduction of body fat and an increase of lean mass after the consumption of a 15% fat diet for 6 months with green tea or black tea.
Eleven clinical studies in 2011 showed that a mixture of tea catechin-caffeine, which is rich in black tea, could have a positive effect on fat oxidation. and on energy expenditure by 4.7% over 24 hours.
- Prevention of diabetes – A 2012 study with data from 50 participating countries in the World Health Survey identified a linear statistical correlation between tea and diabetes, while an in-vitro study had shown that tea improved insulin sensitivity and activity.
- Prevention of hypertension & stroke — Cross-sectional and longitudinal studies indicate a reduction in LDL levels, oxidative damage and inflammatory markers.
- Prevention of Alzheimer’s disease — Long-term administration of green tea catechins lessened Aß-induced cognitive impairment in animal models by increasing anti-oxidative defences. Theaflavins (TF1, TF2a, TF2b and TF3), the main polyphenolic components found in fermented black tea, demonstrated their potential as inhibitors of amyloid-ß (Aß) and a-synuclein (aS) fibrillogenesis.
This was while theanine has glutamate antagonism, important in the prevention of neuronal death.
According to Prof. Williams, epidemiological studies have provided evidence that higher tea consumption could be related with slower cognitive decline, reduced risk of progression from mild cognitive impairment to Alzheimer’s disease and reduced mortality in patients with Alzheimer’s disease.
When concerns about contaminants in tea were raised by the audience during the discussion following the lecture, an expert from the tea industry, Dr. Dan Seevaratnam was quick to point out that “tea seemed to be clean” for Sri Lankans have been imbibing this beverage for a long time without adverse effects.