ARTICLE
Auteur(s) :, Michelle Jones
Technical Manager Europe, ADM Natural Health and Nutrition
Church Manorway Erith Kent DA8 1DL, UK
With almost 70 000 cases of skin cancer reported in the UK each
year [1], the public are increasingly being made aware of the
dangers associated with excessive exposure to the sun, which has
been identified as a major factor in skin cancer incidence. Yet,
people continue to flock to warmer climes in pursuit of the perfect
suntan, with a view to taking their own preventive action to
minimise cancer risks.Already recognised for its nutritional and
health benefits, vitamin E has been identified in recent scientific
research as potentially being an aid to protecting the skin from
external damage caused by harmful ultraviolet rays, environmental
pollutants and oxidative stresses, when topically applied.
Consequently, manufacturers of cosmetics are now realising the
potential of vitamin E and increasingly incorporating it into
skincare products such as moisturisers and sunscreens.Here, we
examine the natural skin protecting properties of vitamin E, its
depletion in dermal layers and benefits of supplementation. We also
cite key studies into the topical application of vitamin E and the
impact on future product development.
Protecting skin naturally
The skin is the body’s first line of defence against the effects of
atmospheric contaminants such as cigarette smoke and ultraviolet
radiation. Although vitamin E is naturally present in the skin,
studies have shown that it is susceptible to ultraviolet-induced
depletion [2]. Levels of vitamin E are at their lowest near to the
surface of the skin, and increase towards the deeper layers.
Researchers at the University of Jena have proposed a mechanism for
the supply of vitamin E to the skin [3].
Researchers found that parts of the body with the highest
concentrations of vitamin E also had a higher sebaceous gland
density (sebum-secreting glands provide skin with some protection
against harmful bacteria). These results suggested that vitamin E
is supplied to the skin via sebaceous glands. This observation was
further supported by the finding of a positive correlation between
the levels of vitamin E and squalene in skin surface lipids
(squalene is a marker of sebum secretion). Sebaceous gland
secretion was found to be an effective means of transferring
dietary vitamin E to skin where it may help protect both skin
surface lipids and the upper stratum corneum (the outermost layer
of the skin) from harmful oxidation.
Vitamin E explained
Four forms of vitamin E are present in nature: alpha-, beta-,
gamma- and delta-, and although gamma is the most abundant
naturally-occurring form of tocopherol in the human food supply
chain, it is the alpha form, d-alpha-tocopherol or
RRR-alpha-tocopherol, that is retained primarily by the human body.
Natural-source d-alpha-tocopherol is one stereoisomer whereas the
synthetic “dl-alpha-tocopherol” is a combination of eight
stereoisomers, only one of which is identical to
d-alpha-tocopherol. The remaining seven stereoisomers have
different stereochemistries, with resultant lower biological
activity relative to the RRR isomer.
Tocotrienols are closely related to the tocopherols and are also
present in some oil-bearing crops at low levels. Tocotrienols
differ from tocopherols by containing three double bonds in the
phytyl side chain. These double bonds give the tocotrienols
fluidity, enabling the body to incorporate them into cell membranes
with ease. Compared with tocopherols, it has been proposed that
tocotrienols may provide additional benefits [4].
Tocopherols versus tocotreniols
Alpha-tocopherol is the most abundant form of vitamin E naturally
present in the skin, although there are also small amounts of
gamma-tocopherol, as well as alpha- and gamma-tocotrienol. In
research demonstrating the presence of alpha- and gamma-tocotrienol
in the skin, it has also been proposed that tocotrienols may offer
skin barrier protection and growth-modulating properties [4], in
addition to antioxidant activity and photoprotection.
In a study at the department of dermatology at the Goethe
University in Frankfurt, the antioxidant capabilities of
tocopherols and tocotrienols in the epidermis were compared using a
free radical scavenging technique [4]. Using this technique, no
significant free-radical scavenging was observed for either alpha-
or gamma-tocotrienol, whereas significant free-radical scavenging
was demonstrated for both alpha- and gamma-tocopherol.
Data from this study along with observed levels in human skin
suggest that alpha-tocopherol is quantitatively the most important
form of vitamin E for protection against free radical attack. This
is further emphasised by the comparison of levels of
alpha-tocopherol and gamma-tocopherol depletion after skin was
subjected to intense UV exposure: alpha-tocopherol was depleted by
0.75 MED (Minimal Erythema Dose) whereas gamma-tocopherol was
depleted only after a very high dose [2] (( figure 1 )).
Vitamin E in sun protection products
Vitamin E is available commercially as both the free alcohol and in
esterified forms; both forms are used in topically applied skin
protection products, but which is best?
Animal studies have demonstrated that topical application of the
free tocopherol form may prevent skin cancer and also inhibit
ultraviolet (UV) B-induced immune susceptibility [6]. Subsequent
studies in both animal and human skin models have compared the
effects of the alcohol form versus esterified forms [5,6]. Results
from these studies have been somewhat variable depending on which
ester form has been used. In these studies, the alcohol form shows
the highest efficacy as determined using measures such as degrees
of sunburn, blistering and skin discolouration. However, the
acetate form has shown little or no benefit using the same
measures, but surprisingly some benefits have been noted for
tocopheryl succinate.
In order to try to understand the observed differences in the
effectiveness of the acetate and succinate forms, skin samples
treated with each of these two forms analysed following irradiation
have demonstrated some liberation of the bioactive free alcohol
from the skin samples treated with tocopheryl succinate, but very
little free alcohol in the skin treated with the acetate [6].
Although this data suggests potential benefits from the use of the
succinate derivative compared with the acetate, the mechanism by
which the free alcohol may be liberated from the succinate in skin
is still not known.
Ingestion versus topical application
All the above studies have concentrated on topical application of
tocopherols and tocopherol derivatives, but as discussed
previously, tocopherols can be secreted into skin layers from
dietary depots via the sebaceous glands. The relative benefits of
tocopherols supplied by these different routes have been
investigated in recent animal studies [7].
In these studies, reductions in skin blistering and pigmentation
via topical application of the free alcohol and the succinate forms
have been compared with reductions from oral consumption of the
acetate form. All three treatments demonstrated benefits in terms
of reduced blistering, although the alcohol form was the most
effective. Each treatment also showed positive benefits in relation
to levels of pigmentation, but in this latter case, similar amounts
of benefit were seen for both topical application of the alcohol
form and oral intake of the acetate form. In the same study
conducted by the Department of Medicine at the Carbrini Medical
Centre in New York demonstrated that the topical application of
succinate and the consumption of the acetate were seen to reduce
the number of tumours when skin is subjected to long-term exposure
to UVB radiation [7]. It also revealed a delay in the onset of
tumour incidence. This research indicates that oral consumption of
vitamin E may protect the skin from UVB damage, offering additional
means for safeguarding it against harmful radiation.
Editor’s note: Archer Daniels Midland Company (ADM) is a
world leader in agricultural processing. The Company is one of the
world’s largest processors of soybeans, corn, wheat and cocoa. ADM
is also a leader in soy meal and oil, ethanol, corn sweeteners and
flour. In addition, ADM is building a position in such value-added
products as specialty food ingredients, bioproducts and
nutraceuticals (such as Vitamin E and sterols). Headquartered in
Decatur, Illinois, ADM has over 26 000 employees, more than 270
processing plants and net sales for the fiscal year ended June 30,
2003 of $30.7 billion. Additional information can be found on ADM’s
Web site at http://www.admworld.com.
For further product information, please contact: ADM Natural
Health and Nutrition, Church Manorway, Erith, Kent, DA8 1DL, UK.
Tel: +44 (0)1322 443 008 Fax: +44 (0)1322 437 536 E-mail:
IngredientsErith@admworld.com
References
1 www.bbc.co.uk/health/conditions/skin_cancer (March 2004).
2 Thiele JJ, Traber MG, Packer L. Depletion of
human stratum corneum vitamin E : an early and sensitive in
vivo marker of UV induced photo-oxidation. J Invest Dermatol
1998 ; 110 : 756-61.
3 Thiele JJ, Traber MG, Packer L. Sebaceous gland
secretion is a major physiologic route of vitamin E delivery to
skin. J Invest Dermatol 1999 ; 113 : 1006-10.
4 Fuchs J, Weber S, Podda M, et al. HPLC
analysis of vitamin E isoforms in human epodermis :
correlation with minimal erythema dose and free radical scavenging
activity. Free Radic Biol Med 2003 ; 34 : 330-6.
5 McVean M, Liebler DC. Prevention of DNA photodamage
by vitamin E compounds and sunscreens : roles of ultraviolet
absorbance and cellular uptake. 1999.
6 Gensler HL, Aickin M, Peng YM, Xu M.
Importance of the form of topical vitamin E for prevention of
photocarcinogenesis. Nutr Cancer 1996 ; 26 : 183-91.
7 Burke KE, Clive J, Combs Jr. GF,
Commisso J, Keen CL, Nakamura RM. Effects of topical
and oral vitamin E on pigmentation and skin cancer induced b
ultraviolet irradiation in Skh :2 hairless mice. Nutr Cancer
2000 ; 31 : 87-97.
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