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Sun damage or photo damage produces
both skin cancers as well as photo-aging. Photo-aging shows
itself on the skin as wrinkling, scaling, dryness and mottled
pigmentation. Ultra-violet light is absorbed by skin, which
in turn produces a photo-chemical reaction. The UVA light
is absorbed by both DNA as well as urocanic acid. The photo-chemical
reaction produces oxidation of both DNA, nucleide acid and
protein as well as lipids. This is known as oxidative damage.
Anti-oxidants have been evolved to protect against and reverse
some of the damage produced by sunlight. An anti-oxidant mechanism
is very advanced in plants that protects against the damage
from sun exposure.
Oxidation is produced by reactive oxygen
molecules.
The DNA absorbs ultra-violet light mostly
in the UVB (290-320 manometres) range. This produces damage
mainly within the epidermis. UVA (320-400 manometres) penetrates
deeper into the skin and produces damage in the epidermis,
the dermis as well as affecting blood vessels. The UVA has
a much more oxidizing effect on cells.
The carcinogenic or cancer forming effects
of ultra-violet B produce mutations within the DNA. This initiates
tumours within the epidermis. The UVA promotes these tumours
as it has much more oxidizing stress on the skin than UVB.
It may as a result be more cytotoxic and immunosuppressive.
Sunscreens certainly protect against
ultra-violet light. The sunburning spectrum is UVB and sunscreens
are very effective. Ultra-violet A is the most difficult to
protect against. It is important to realize that the SPF numbers
are calculated with an amount of sunscreen on skin that exceeds
what most of us put on our own skin. The SPF is calculated
with a quantity of 2mg. of sunscreen per centimetre2. Most
people will put on about half to a one quarter of this when
used as sun protection. Unfortunately low quantities of sunscreen
of per centimtre2 will have minimal sun protective effects.
Usually if 5mg. per cm.2 of sunscreen is applied to the skin
the sun protective factor is in the region of an SPF of 3.
Anti-oxidants play a significant part
in the protective and repair mechanisms within animals and
plants. This can be achieved by anti-oxidants that are produced
within the skin itself or by those consumed or applied from
plants. The anti-oxidant effects can be divided into those
that have their protection through enzymes and those that
tend to reduce the quantity of hydrogen peroxide as well as
lipid hydroperoxides.
The use of topical anti-oxidants
has certain requirements. These have to be stable as well
as being cosmetically acceptable. It is clear that anti-oxidants
have a photo-protective benefit.
The physiological anti-oxidants include
vitamin C, vitamin E, and ubiquinol.
Vitamin C is water-soluble and is a free
radical scavenger. It is required for collagen synthesis and
may inhibit elastin formation in the dermis. It may also reduce
pigment synthesis as well as enhance epidermal barrier function.
For it to be active it must be present on the skin at a pH
of 3.5 or lower in order to have an anti-oxidative effect.
Vitamin E is different from vitamin C
in that it is lipid soluble. There is evidence that combining
vitamin E and vitamin C may be of some benefit.
Other anti-oxidants to be considered will
be selenium as well as zinc.
Plants synthesize vitamin C, vitamin
E and flavones and polyphenolic compounds.
1) Silymarin
2) Soy isoflavones
3) Tea
4) Polyphenols
These are all potent plant anti-oxidants.
- This is a Milk Thistle extract. The main component in terms
of anti-oxidants is silybyn. This prevents lipid peroxidase
action. It also has been shown to inhibit tumour promotion
in animals.
- Soy has been connected with a reduction in cardiovascular
disease and in some incidents of breast cancer when taken
by mouth in large quantities. It has a phytoestrogen effect,
which can reduce menopausal symptoms.
The isoflavones are genistein and gaidzein.
The genistein has a collagen synthesis
effect. It is also anti-cancer. It has been used both orally
as well as topically. The genistein is a powerful scavenger
of peroxyl radicals. This has a significant reduction in lipid
peroxidase activity. It has been shown to reduce redness in
the skin of mice which are subject to ultra-violet A. It also
has an anti-inflammatory effect. The use of this compound
reduces the immune suppression effect of ultra-violet light.
Tea is fermented initially to green
and then to black tea.
The drinking of black tea has been shown
to reduce the frequency of squamous cell carcinomas.
Work done with green tea both topically
and taken orally shows that it reduces the ability of ultra-violet
to produce skin cancers and redness, particularly in animals.
The possibility of combining tea plus vitamin E to work together
as anti-oxidants is interesting.
Much more work needs to be done in order
to establish how combining anti-oxidants with sunscreens will
have a very beneficial effect on reducing sun damage to skin. |
acne.ca
