Tea & Healthy Ageing

This essay was produced for Dilmah by Dr. Wester Modder, Scientist (former head of the Tea Research Institute) and author of several books on the health benefits in tea. It describes succintly, the impact of regular consumption of tea on the process of ageing.

“Balm of hurt minds, great nature’s second course,
Chief nourisher in life’s feast.”
Shakespeare, Macbeth

Although that line from the Bard refers to sleep, it could well be pressed into service to pertain to tea, as we shall try to show in a new series of essays of which this is the first.

These are perhaps fanciful images but to many of us tea is ‘nourisher’ and ‘nature’s second course’.

‘True’ Tea is Camellia sinensis

Tea sensu strictu, the tea laden with proven healthful attributes, comes from the terminal shoots of the tea plant which in botanical taxonomy is Camellia sinensis (L.) O. Kuntze (family Theaceae).  No other species of plant gives the ‘true’ tea that feeds a huge global demand.

The Types of Made Tea

Tea may be drunk hot, or cooled, or ice-cold, with or without milk and sugar, depending on preference and circumstances, but it is initially a hot-water extract of the processed C. sinensis shoots (ideally, the topmost two immature leaves and terminal bud).  The processing (or manufacture) of the shoots is carried out to varying degrees and by different steps, resulting in black, green, white or oolong teas.  Black, green and white refer to the finished product, the ‘made tea’, and not to any colour in the fresh leaf or the tea plant growing in the field.

The shoots being processed turn black (or dark brown) when they are left to wither in hot air, are macerated or cut, and finally left exposed to the atmosphere to oxidize.  Black tea is the end result.  (In a similar manner, fruit such as bananas and apples when cut and left exposed darken or turn black.)

Green tea results when the shoots are withered and then steamed or subjected to dry heat for a short time, the colour approximating to that of the fresh green leaf.  There is no maceration stage.

For white tea, the shoots are only steamed, and not withered as for green tea.

In the making of the darker-coloured oolong tea, oxidation is carried out but not for the same length of time as for black tea.

Although made tea, whether black, green, white or oolong, or any of their respective subsets, has the same starting material, namely plucked shoots of Camellia sinensis, certain of the varieties or cultivars of C. sinensis may be discerned as being preferable for manufacturing one or other of the tea types.

Antioxidants and Free Radicals

In our new, health-conscious world, terms like ‘antioxidants’ and ‘free radicals’ have moved from the pages of biochemical texts into the everyday discourse of knowledgeable men and women.

Many of us are aware these days that entities known as free radicals are generated in our bodies, and that antioxidant molecules, many of them in food, can prevent these free radicals from bringing on degenerative and progressive conditions and illnesses.

Free radicals are given off not only during normal metabolism, but also in response to an assortment of extrinsic factors (psychological stress, environmental pollutants, an excess of fats in the diet, a lack of vitamins, some food additives such as nitrates, tobacco smoke and ingested alcohol).  Free radicals are abundant during aging.

The cells’ structural components (membranes, the nucleus, DNA), and their chemical constituents (proteins, lipids, carbohydrates), are destroyed by free radicals.  Consequently, they cause more than fifty degenerative and chronic diseases, and are responsible for hastening the impairment associated with aging and for bringing on that state prematurely.

An account of antioxidants, and their organization in the human body into systems of defence against ravening free radicals, is given by Modder and Amarakoon1.

In Tea: One of the Most Powerful Antioxidants Known

Many alternative, so-called herbal ‘teas’ are retailed around the world.  A proportion of these non-Camellia sinensis teas are beneficial, as are indeed plant-derived foods in general because plants used for food would naturally contain a range of beneficial molecules.

One class of such molecules, the flavonoids have, over the past decade or so, been shown to be the most effective antioxidants found in nature.  Flavonoids belong to the larger grouping of polyphenols, and they are commonly found in vegetables and fruit.  Notably, they are present in singularly high concentrations in the teas made from C. sinensis, as well as in soy beans and red wine (vide Modder and Amarakoon1; Table 3).  As a result, the antioxidant activity in tea is much higher than in a whole range of vegetables and fruits (vide Modder and Amarakoon1; Tables 3 and 8).

Flavonoids in the diet are important, because they protect against a surprisingly large variety of diseases and degenerative conditions owing to their antioxidant and anti-inflammatory properties.  On top of this, independent scientific and clinical research in different parts of the world has proved remarkably convergent in showing that, in imparting health benefits, tea flavonoids lead all the rest.

One of these flavonoids, epigallocatechin gallate, present in precisely those parts of the tea plant, the tender shoots, from which tea is made, is one of the most powerful antioxidants known.

Tea bestows a range of benefits, including neutralizing or mitigating effects on toxins and pollutants, and on some of the ravages of the aging process.  Examples of these effects are mentioned in this initiatory essay.  Other benefits will be the subject of future essays.

Tea in Detoxification

in addition to supplying material for growth and replacement, and for energy production, a prime function of our food is detoxification of potentially damaging chemicals which either enter our bodies or are produced within them.  Tea is one of the elements in the diet that helps in this function, and drinking tea could well prove a wholesome habit in these times of increasing environmental pollution.

Dr John H. Weisburger2 of the Institute for Cancer Prevention, American Health Foundation, New York, reported a finding, in 2003, which indicates that detoxification enzymes can be induced by tea.  Work in his laboratory had shown that levels of the metabolic enzymes, cytochrome P-450 and UDP-glucuronosyl transferase, found in the liver and involved in the detoxification of many environmental chemicals and pollutants in the body, increase when rats are given a two per cent solution of tea for six weeks.

Tea for Healthy Aging and Longevity

Dr Weisburger2 also concludes from recent studies that six or more cups of tea per day helps healthy aging.  Thus, tea can restore elasticity to the skin, and tests have shown that it enhances memory.

In populations where regular tea drinking is a part of the lifestyle, as in Japan and India, individuals live to an advanced age in good health.  Also, experimental studies indicate that animals given dietary antioxidants, including tea, live longer.

Tea and Alzheimer’s Disease

Dementia is defined as an “impairment of intellect, memory, and personality but without impairment of consciousness.”  One type of dementia, most often affecting the elderly, is Alzheimer’s disease.  This is caused by degeneration of nerve cells or neurons in the brain, which are then replaced by protein deposits or ‘plaques’.  Senility, or premature senility, is the result.

It is reported that of the order of 10 million people around the world are afflicted, although among the elderly in the tea-drinking populations in Japan and India the incidence of Alzheimer’s is low.

Dr Edward J. Okello3 and colleagues at the Medicinal Plant Research Centre of the University of Newcastle-upon-Tyne, England, reported, in 2004, that both black and green tea have similar effects to drugs that stop the development and progression of Alzheimer’s disease.  Tea inhibits enzymes associated with the onset of the disease, but coffee has no significant effect.

Alzheimer’s disease is characterized by a reduction in the amounts of the neurotransmitter, acetylcholine.  Acetylcholine is liberated into the synapses at nerve-cell endings where it is instrumental in transmitting nerve impulses to other nerve and muscle cells.  Once liberated, it is necessary, for continued transmission, that acetylcholine be broken down rapidly by an enzyme, acetylcholinesterase.  However, in subjects with Alzheimer’s disease, there is enhanced acetylcholinesterase activity, and the normal, fleetingly high levels of acetylcholine cannot be attained. Nerve-impulse transmission is thus impaired.

Drugs used to slow progress of the disease serve to inhibit acetylcholinesterase activity, and this allows acetylcholine levels to build up at the synapses in a normal manner.  Dr Okello and his team have now found that tea consumption gives the same results as the drugs, but with none of the side-effects.

Tea inhibits another enzyme, butyrylcholinesterase, found in characteristic protein deposits in the brains of subjects with Alzheimer’s disease.

A third enzyme, beta-secretase, which is involved in the development of the protein deposits, is inhibited by tea, but only by green tea, according to this report.

It is also stated that the inhibitory effects of green tea lasts for a week; that of black tea for a day.

Preliminary evidence suggests that about 10 cups of tea per day are necessary to bring about beneficial effects in subjects with Alzheimer’s disease.  A medicinal tea is now being aimed at, specifically for Alzheimer sufferers.

A spin-off from this study is the pointer that regular tea consumption enhances memory, since the enzymes in the brain that tea inhibits are associated with this function.  It is already known that the caffeine in tea improves memory and mental alertness.

Tea and Parkinson’s Disease

Parkinson’s disease, another degenerative, progressive disease of the nervous system, affecting mainly the middle-aged and the elderly, results from dysfunction in the brain’s limbic system which is said to be concerned with visceral processes, particularly those associated with emotional states.  The dysfunction is caused by a deficiency of the neurotransmitter, dopamine.

Parkinsonism can result from a broad range of damage to the brain, like that occurring from exposure to neurotoxins in the environment, including pesticides as has been found recently.

Dopamine is produced in a group of nerve cells, called the substantia nigra, situated in the limbic system.  The neurotransmitter moves from here through pathways in nerve bundles to another part of the limbic system, called the corpus striatum, where sufficient amounts need to be localized to bring about normal muscle movements.

However, in Parkinson’s disease, the dopamine-producing cells selectively die and so less of the neurotransmitter is produced.  Also, there is an abnormal back-flow of dopamine from the corpus striatum to the substantia nigra.  Normal muscle movements are therefore not possible and Parkinsonism, characterized by rigidity and tremors of the limbs, results.

In 2002, Dr Tianhong Pan4, from the Baylor College of Medicine, Houston, Texas, reported experiments with green tea which showed that polyphenols in the tea can protect animal models from Parkinson’s disease, and may therefore have potential for treating Parkinsonism in humans.

A low prevalence of Parkinson’s disease observed in populations in parts of Asia (44 per 100,000 of the over-50s in China, compared to 250 per 100,000 in Europe), and in parts of Africa, where green tea consumption is common, led Dr Pan and colleagues at the Shanghai Second Medical University, China to examine the effects of green tea polyphenols on the uptake both of dopamine and of a neurotoxin (MPP+), by mouse brain nerve cells in culture.  They found that dopamine uptake decreased dose-wise, by 65 to 80 per cent.  MPP+ uptake was also blocked.

In vivo administration of the polyphenols to rats intraperitoneally, in doses of 0.1 to 0.3 mg, caused dopamine uptake by brain nerve cells to decrease from 60 per cent to 47 per cent.

From these results, it appears that tea polyphenols may prevent Parkinson’s disease by cutting down the entry of neurotoxins from the environment into brain nerve cells.  Polyphenols may also relieve Parkinsonism, if already established, by causing dopamine to accumulate outside the nerve cells, in the synapses, where it would regain its function as a neurotransmitter.  Further, the polyphenols can halt the back-flow of dopamine out of the corpus striatum.

The amounts of tea administered to the animal models in the experiments were the human equivalent of 3–10 cups of green tea per day, one cup being defined by the researchers as a hot-water extract of 2 g of leaf in 100 ml.

Dr Pan was not clear whether pharmacologically-effective levels of polyphenols can be attained in blood, brain and other tissues simply by drinking tea.  Establishing this, and the clinical effects of polyphenols on patients with Parkinson’s disease, require further study.

It must be noted that in this study on Parkinson’s disease, as in many other studies into the multifarious effects of tea, green tea alone was used, although black tea, as well as a variety of other plant sources, contain polyphenols and the pharmacological activity associated with them.

Conclusion: the Meaning of Aging

Let me conclude this essay by drawing attention to the results of a study, published in June 2005 in the science journal Nature, by Dr Warren Sanderson of the University of New York in Stony Brook, and Dr Sergei Scherbov of the Vienna Institute of Demography.

The meaning of aging has been redefined.  It is not the number of years lived that is important; what is important is the number of years left to live.  As life expectancies rise, populations in effect become younger.

The glass is not half full but half empty.  Perhaps the older among us can now look more optimistically at the approaching ‘empty’ years, and revitalize our second-time-around youth with many more cups of the uniquely beneficent brew.

References

1 Modder, W. W. D. and Amarakoon, A.M.T. 2002.  Tea and Health.  The Tea Research Institute of Sri Lanka, Sri Lanka; 180 pp.

2 Weisburger, J.H. 2003.  Personal communication.  Institute for Cancer Prevention, One Dana Road, Valhalla, NY 10595.

3 Okello, E.J. et al. 2004.  In vitro anti-beta-secretase and dual anti-cholinesterase activities of Camellia sinensis L. (tea) relevant to treatment of dementia.  Phytotherapy Research 18, 624 – 627.

4  Pan, Tianhong 2002.  Poster Presentation, 54th Annual Meeting, American Academy of Neurology, Denver, Colorado.