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Issue 65
Antioxidants - The Silent Protectors
Antioxidants have become the focus of much media attention
which has lead many people to recognise the word, without knowing what they
are for and what they do. An antioxidant is any compound, which has the ability
to protect against the biological process known as oxidation. If oxidation is
allowed to damage the intricate structures of a cell, then this is referred
to as oxidative stress. We all know oxygen is essential for us to stay alive,
but many people do not know that oxygen, in a different form, is probably the
cause of almost all diseases known to man. The very first stage in the progression
of diseases such as cancer and heart disease is caused by what are known as
oxygen free radicals, or reactive oxygen species (ROS).
Many people know that the chemical formula for oxygen
is O2 and in this form it is perfectly stable and safe. However, when this formula
is disrupted, oxygen can become very reactive, volatile and a danger to cells.
These extremely volatile compounds are produced in our bodies every second as
a by-product of our metabolism and are simply an oxygen atom with an un-paired
electron. This molecule will then try to find a suitable donor to ‘pair-up’
with its spare electron and will subsequently attack anything in its path, including
DNA and cholesterol molecules, until it is happy that all of its electrons have
a partner. It is these rather selfish attacks which cause the damage that leads
to the above mentioned diseases. It is at this point where antioxidants are
so useful. They could be described as a Kamikaze nutrient as they sacrifice
themselves in order to protect the contents of the cell from the endless attack
from ROS.
Instead of the ROS attacking cellular structures to gain
the missing electron, they will attack the antioxidants and this is how they
can protect our cells. Important dietary antioxidants include vitamin C, vitamin
E, vitamin A selenium, beta-carotene, lycopene and lutein. The human body does
have its own antioxidant protection system, which consists of a group of compounds
produced by the liver. However, considering that each and every cell in the
body is attacked by ROS a staggering 10,000 times each day, this system is already
under strain, but can cope. It is only when this system is overwhelmed with
ROS that dietary intervention is essential and unfortunately, this is the case
most of the time with today’s climate and lifestyle. There are many environmental
factors which can cause this added strain on our defence system which include
increased UV light exposure (due to the hole in the ozone layer), smoking, pollution
and even barbecuing food. It is for these reasons that an adequate daily intake
of antioxidants is vital, as it is only when our defence system can no longer
cope with the increased ROS production do diseases begin to develop.
Therefore it is beneficial to include plenty of foods
containing antioxidants in the diet and there is a very simple method of assessing
whether a food contains antioxidants. This can be done just by looking at the
food and seeing how brightly coloured it is. This is because most of the antioxidants
are actually the compounds in fruits and vegetables which give them their colour.
For example beta-carotene, which tends to give the fruit an orange or yellow
colour, is a potent antioxidant as is lycopene, which is the compound responsible
for giving tomatoes their characteristic red colour. This is one of the many
reasons why it is recommended that we consume at least five portions of fruit
and vegetables every day, as this will provide the extra antioxidants needed
to fight ROS, as well as being an important source of dietary fibre. Supplements
should also play an important role in providing these nutrients as there are
certain circumstances which require levels of antioxidants that cannot be provided
by diet alone. One such circumstance is a prolonged exposure to sunlight as
is usually the case when we go on holiday.
It is now advised that if we are going abroad to a country
which is sunny and hot and our skin will be exposed to more sunlight than it
is used to, then we should start taking antioxidant supplements at least two
weeks before to build up extra protection. This is because the harmful UV rays
from the sun, which are penetrating the earth’s atmosphere, are hitting our
skin cells and leading to the production of ROS. These ROS then attack the DNA
in the skin cells which, without sufficient protection and repair mechanisms,
may lead to skin cancer. Consuming antioxidants before we are exposed to the
sun will help to build up an extra protective barrier which will help to prevent
these ROS from attacking the DNA and therefore may prevent the onset of skin
diseases. However, it must be stated that antioxidants alone should not be relied
upon to provide protection from the sun’s rays and sun cream must always be
applied. The skin is not the only part of the human body which can be protected
by an adequate daily intake of antioxidants. The heart and circulatory system
will also benefit from an increased consumption of brightly coloured fruits
and vegetables. This is due to the fact that, as with cancer, the initiation
of heart disease is triggered by ROS.
In this circumstance, the ROS do not attack DNA but they
attack the bad form of cholesterol, which is referred to as LDL. When this LDL
is attacked it becomes oxidised and can then enter the blood vessel wall where
it causes the formation of a plaque. If this plaque is allowed to grow and cause
a blockage in the blood vessel then blood flow to the area beyond the blockage
will be restricted which may cause the death of the tissue. If this kind of
blockage occurs in the coronary artery (the blood vessel supplying the heart),
then a heart attack will result. However, if the levels of antioxidants in the
blood are sufficiently high, then the oxidation of LDL is less likely to occur
which in turn will decrease the risk of developing heart disease. It is also
beneficial to try to increase the amount of monounsaturated fat in the diet,
as this type of fat, of which olive oil is a good source, is less susceptible
to oxidation than polyunsaturated fat which is found in most vegetable cooking
oils. There is another situation where antioxidants from food sources may not
be adequate to meet the needs of the body and therefore supplements would be
required. Athletes, or people who partake in strenuous exercise at least twice
a week, find themselves in such a situation.
As mentioned above, ROS are produced in our bodies every
second as a product of our metabolic process (the breakdown of food to provide
energy), and those who lead more sedentary lifestyles should reduce the threat
or ROS by dietary means alone. However, athletes are at an increased risk of
damage caused by oxidative stress, as, on average, their metabolic rate is much
higher. A high metabolic rate causes increased ROS production and therefore
an antioxidant supplement may help to boost the levels offered by fruit and
vegetables and provide extra protection. Although it is well established that
brightly-coloured fruits and vegetables including peppers, tomatoes, carrots,
strawberries, blackberries and grapes are naturally high in antioxidants, there
are other dietary sources which are less obvious. One such source is tea.
Therefore many people will be unaware that while they
are gaining refreshment from their usual consumption of tea throughout the day,
they are also consuming antioxidants which may help prevent the onset of the
above mentioned diseases. Another good source is red wine, which is the reason
behind the recommendation to consume one glass of red wine each day to help
prevent heart disease. It should also be noted that although tomato sauce is
usually high in sugar, it is also a good source of lycopene, which has been
shown to have the ability to protect against prostate cancer, heart disease
and age related macular degeneration. In conclusion, the recommendation for
the consumption of five portions of fruits and vegetables a day should seriously
be considered from an early age as fatty streaks, which are the first signs
of heart disease, have been observed in children as young as three years old.
With the stresses and strains of modern life, this advice
has never been so important as it may be the answer for reducing the incidence
many chronic diseases, which have rapidly increased over last ten years adding
extra strain on the already stretched National Health Service. Simply by placing
an apple in childs lunch box every day, instead of a biscuit or chocolate bar,
could lead to a longer and disease free life. It is also never too late to start
a new dietary regime as regular consumption of antioxidant containing fruits
and vegetables could help the body to rid itself from diseases that may have
already begun.
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