MadSci Network: Medicine

Re: Does having carotene make a difference?

Date: Thu Oct 22 10:07:35 1998
Posted By: J.M. Wingert, Staff, Center for Comparative Medicine, Baylor College of Medicine
Area of science: Medicine
ID: 908017580.Me

Skin color is influenced by three substances: hemoglobin, carotene, and, 
most important, the pigment melanin. Your entire epidermal area (your skin) 
contains some portion of a pigment called melanin. Melanin is nature's 
substance, which gives your skin and hair its color. Melanin is present in 
the iris of the eye and may be found in the sclera (white part of the eye). 
The powerful thing about melanin, is that it provides more benefits to you 
than adding color to the skin, hair and eyes. 
Nature has provided you with its most powerful ultraviolet (UV) protection
against the harmful rays of the sun. It is nature's own sunblocker. 

The idea is deeply entrenched that melanin evolved primarily as a 
sunscreen. There is a north-side gradient in skin color. Darkly-pigmented 
races are clustered in the sunny tropics. Light-skinned people inhabitat 
foggy northern climates. Skin cancers are rare in African American people 
and quite uncommon in moderately pigmented Asiatic people. Photoaging, the 
actinically-induced appearance of premature aging, (dermatoheliosis) is 
scarcely noticeable in older African Americans. Wrinkles are
minor or absent until later in on in the aging process.

Very simply, sunburn and UV light can damage your skin, and this damage can 
lead to skin cancer. The effect UV light has on your skin is dependent both 
upon intensity and the duration of your exposure. How your skin reacts to 
the amount of exposure received is related to your genetic background. Even 
if you rarely burn, sensitive areas such as your lips, nose, palms of the 
hands and soles of the feet should be protected, in addition to the exposed 
areas of the skin.

It is well-established in science that the incidence of melanoma and other 
cancers of the skin is on the rise (more than 800,000 new cases per year), 
and that solar radiation, particularly that in the UV range, is a major 
causative factor. In this regard, individuals with high skin melanin 
content are less likely than those with lower melanin content to suffer 
from skin cancers (basal and squamous cell carcinomas, melanomas) and other 
solar-induced damage (wrinkling, solar lentigines).

What is Melanin?

Melanin is not a single compound. Melanin refer to a class of compounds 
which are defined in the Merck Index as the pigments responsible for the 
color of skin, hair, feathers, fur, and soil. Melanin are highly irregular 
polymers produced in the form of granules which may be bound to protein
material. Some classes of natural melanins include allomelanins, 
phaeomelanins, and eumelanin. However, eumelanin is the predominant 
epidermal melanin and is discussed here.


Sunlight Your Skin's Worst Enemy

Melanin particles both scatter and absorb ultraviolet and visible light 
smoothly over a broad spectral range. In spite of all the warnings, people 
don't take sunburn seriously. Every sunburn is an injury, and injuries are 
cumulative over the years. During the tanning process the sun stimulates 
the melanocytes to produce and liberate more melanin for skin protection. 
But until the melanin reaches the skin's surface and can protect you, the 
skin is left vulnerable and can be heavily damaged and

Sunlight, especially its UV-part, supported by infrared, is the notorious 
enemy of the skin. Every sign of aged skin is supported by sunlight: 
blemished and blotchy, loose and inelastic, rough and wrinkled
skin. These same rays have been implicated in causing cataracts of the 
eyes. Today, we also know that the skin plays an important role in the 
immunological defense of the body. Sunlight has positive and negative 
effects. A balanced protection against these rays is very important. UVR 
may be present at unsafe levels even on cloudy days. 

Since skin cancer rates correlate inversely with pigment, it is generally 
assumed that melanin is photoprotective. Melanin is generally thought to be 
photoprotective since skin cancer risk is inversely proportional to degree 
of skin pigmentation.

To look at the undisputed scientific benefits of melanin, we must look at 
the effects of what naturally occurring melanin has on people. African 
Americans do sunburn and seem to be clinically exempt from the well know 
signs of premature skin aging as seen in White Americans. African Americans
rarely show deep wrinkles and the other stigmata of dermatoheliosis, 
depigmentations, leathery-dry skin, elastosis, sags, etc. The epidermal and 
dermal changes from chronic exposure to solar radiation have been 
thoroughly described in photoaged Whites. As far as carcinogenesis is 
concerned, and to some degree the connective tissue damage, Melanin or 
other pigments in human skin protect it. 

Melanin Nature's own Protection for the

Your skin has the ability to develop certain mechanisms of protection 
against the sun's rays. Science has shown indisputably that the most 
effective protection is the development of the skin pigment
Melanin, which is induced by UVR, Melanin, a complicated biochemical 
reaction, is induced by UVR. There are two different types of melanin: the 
black brown eumelanin and the yellow/red phaeomelanin.


The Function of Melanin

Melanin's number one function is the protection of the skin, hair, and eyes 
against the damaging effects of sun's the UVR. Melanin is the umbrella of 
our skin; the deeper layers are also protected.
One of the most important effects of melanin is the absorption of heat 
which works most effectively in people who have the most melanin in the 
skin. Melanin absorbs more or less totally over the whole range of visible 
and infrared light in the upper layer of the skin. The heat is transferred 
to the outside world. 

After sun exposure, biosynthesis of melanin in the skin needs 3-8 days to 
develop. There is no protection in the decisive first days, persons with 
Light skin produce very little melanin. They have no effective UV 

Another huge plus for melanin is that it is a effective neutralizing agent 
for free radical scavengers--molecules which are harmful to the human body. 

Scientific information was obtained from the book: Melanin: Its role in 
human Photoprotection, Editors: Lisa Zeise, Miles R. Chedekel, and Thomas 
B. Fitzpatrick. 

June Wingert RM(ASM)
Center for Comparative Medicine
Department of Pathology
Baylor College of Medicine
Houston, Texas

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