For centuries, people have attributed many favourable benefits to tea. Today, their assumptions are being confirmed as research shows that drinking tea can help prevent certain diseases. This arises from the antioxidants found in tea leaves. Eric Russell reports.
Antioxidants are compounds that neutralise the damaging effects of free radicals, those chemicals that damage normal cells.
Simply stated, a free radical is an atom or molecule with an unpaired electron. Unpaired electrons make for very unstable, highly reactive atoms and molecules. This means they can easily bond with another molecule or atom. This in turn, creates chemical reactions that can wreck havoc on the body. In comparison, paired electrons represent a far more stable state.
Free radicals form as a by-product of normal cellular activity. In addition, exposure to ultraviolet light, pollution, and cigarette smoke also contribute to free radical formation.
Even diet and stress can affect their level in the body. This is important because excessive formation can damage cells and tissue. Researchers also believe free radical damage contributes to aging.
A healthy cell becomes a free radical when it loses its electron to any of the numerous attacks that take place in the body millions of times each day.
An antioxidant contributes one electron per molecule to the free radical to neutralise it or render it harmless. Once the antioxidant donates its ion, it then becomes a free radical. This is known as an ion cascade.
Oxygen, critical for life, is a main source of free radicals. During cellular respiration some oxygen molecules are converted into free radicals when one of the electrons in the molecule is lost.
This turns oxygen into a hyperactive chemical that cannot rest until it gets an electron back. The only way it can replace the missing electron is to take it from another molecule. If that other molecule happens to be a part of a healthy cell, then the cell will be damaged. This could lead to a number of diseases or could induce it to grow uncontrollably and form a tumour. Increased production of free radicals in the body results in oxidative stress.
Natural production
Free radicals are naturally produced in the body every time a person eats or breathes. As long as free radical production is kept at a low level, and enough antioxidants are consumed in the diet to eliminate or reduce their damage, there may be no health risk associated with these free radicals.
However, other environmental factors increase the formation of free radicals: exposure to pollution, sunlight, stress, high-fat diets, alcohol, cigarette smoke, strenuous exercise, inflammation, and radiation. Because most people are exposed to one or more of these additional causes of free radicals on a regular basis and they generally do not consume enough sources of antioxidants in their diet, they are prone to the damaging effects of free radicals.
It is now well documented that our polluted and stress-filled environment has dramatically increased the number of free radicals, or unstable atoms, in our bodies. These excessive free radicals and the damage they cause to our intracellular RNA and DNA has been clearly linked to many chronic degenerative diseases such as cancer, heart disease, strokes, Alzheimer's, rheumatoid arthritis and many others as well as the acceleration of the aging process.
Over 90 human disease states have been linked to the damaging actions of free radicals and may thus be in part attributable to insufficient antioxidant protection.
Each free radical can destroy an enzyme or protein molecule or even an entire cell. The damage is actually even more extensive because each free radical usually generates a chain of free radical reactions, resulting in thousands of free radicals being released to destroy body components.
Damage by free radicals includes that of lipid peroxidation-free radicals which initiate damage to fat compounds in the body, causing them to turn rancid and release more free radicals. Cross-linking-free radical reactions cause proteins and DNA molecules to fuse together.
Membrane damage-free radical reactions destroy the integrity of the cell membrane, which in turn interferes with the cell's ability to take in nutrients and expel wastes. Lysosome damage-free radical reactions rupture lysosome cell membranes. These then spill into the cell and digest critical cell compounds. Accumulation of the age pigment lipofuscin may interfere with cell chemistry.
Help from antioxidants
Antioxidants help prevent or reduce the body's formation of free radicals. The most potent antioxidant and free radical scavenger known to science is N-acetyl cysteine. Other important ones are lycopene, quercetin, bilberry, grape seed extract, co-enzyme Q and milk thistle.
The free radical scavengers called proanthocyandins or pycnogenols are 50 times more powerful than Vitamin E and at least 20 times stronger than Vitamin C. An even more recent discovery is curcuminoids, which are nature's most powerful and aggressive antioxidants known today.
Antioxidant vitamins can slow cell destruction by neutralising free radicals that can cause cell damage. This results in a decrease in the negative effects of aging on the body. Fruits such as peaches, grapes, apples, berries, bananas, prunes and melons are all very high in antioxidant content; as are vegetables such as celery, carrots, string beans, broccoli, cauliflower, squash, onions, beets, and baked potatoes; and nuts and mushrooms.
Antioxidants can prevent damage by trapping free radicals before they have a chance to wreck healthy cells; they provide the missing electron to the free radical, which stops the free radical from attacking and damaging a healthy cell; and they are able to repair molecules that have already been damaged by free radicals, preventing the chain reaction of destruction to healthy cells.
Tea power
Tea, which is one of the most widely consumed beverages across the globe, is a rich source of antioxidant flavonoids. Consumption of these polyphenolic compounds, which are also found in vegetables, fruits and red wine, has been linked with a reduced risk of coronary heart disease, through lower blood cholesterol; strokes; and reduced risk of developing certain digestive and oral cancers.
Some studies show that tea has a higher antioxidant effect than certain vegetables. But adding milk to tea appears to nullify this beneficial effect.
A major proportion of premature deaths in developed countries is due to coronary heart disease and cancer. Free radicals, produced endogenously as a by-product of aerobic metabolism, are implicated in the pathogenesis of these diseases because they have considerable chemical reactivity with biological molecules. Such damage to cellular lipids and DNA increases the risk of developing heart disease and cancer respectively. In addition, there is now considerable evidence that inadequate dietary intakes of antioxidant micronutrients, such as flavonoids and phenolic compounds, which prevent free radical-mediated damage in vivo, contribute to these disorders.
So it is likely that the health of the population could be improved through increased consumption of antioxidant-rich fruits, vegetables and beverages.
Antioxidants can also make life more pleasant for drinkers of alcohol. While too much alcohol has the unwanted effects of a hangover and potential liver damage, anti-alcohol antioxidants can act as a preventive. The thiamine in vitamin B1 is one, but they are better taken before drinking.
Drinking alcohol leads to the production of the toxic compounds acetaldehyde and malondialdehyde. Like most undesirable compounds in the body, these create free radical damage to cells throughout the body. Although antioxidants help prevent cell damage from alcohol, they do not stop the temporary mental impairment that alcohol induces. In addition, they may be relatively ineffective against the regular, high intakes of addicted alcoholics.
All tissues and body fluids contain antioxidants which afford protection against damage mediated by endogenously generated, highly reactive free radicals. Within the cells, this protection is primarily derived from antioxidant enzymes such as superoxide dismutase and glutathione peroxidase.
Most extracellular antioxidant capacity comes from low molecular weight scavenging antioxidants. Many of these are dietary components such as ascorbic acid, alpha-tocopherol and beta-carotene, or are derived from dietary components such as uric acid, non-protein thiols and glutathione. Major plasma proteins such as albumin also have antioxidant activity by virtue of their high sulphydryl content.
There is much research still needed into antioxidants to formalise the empirical information that has been recorded. Antioxidants in saliva, for example, are less well studied or understood than those present in plasma and other body fluids but they contribute significantly to oral health. But if food scientists drink tea while researching antioxidants, they will be helping both themselves and mankind.
