The New Science of Perfect Skin: Understanding Skin-Care Myths and Miracles for Radiant Skin at Any Age - Hardcover

Über die Autorin bzw. den Autor

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Daniel B. Yarosh, Ph.D., is widely recognized as a pioneer in the science of DNA repair. He and his laboratory, AGI Dermatics, are responsible for inventing ingredients for such brands as Estée Lauder, L’Oreal, and Shiseido. His products and cosmetics innovations have been featured widely in the media, including ABC’s World News Tonight, Wall Street Journal, Vogue, Newsweek, Self, Allure, and Good Housekeeping. Visit his Web site at www.agiderm.com.

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ONE
Skin 101

Along with the rest of the body, human skin has evolved over roughly 7,500 generations, give or take a few. These genetically driven changes have been fueled over the millennia by selection for what is optimal for one thing and one thing only: sex.

Yes, that's right: sex, as in human reproduction.

Biologically speaking, skin has the same ultimate purpose as the rest of the human body: contributing to the continuation of the species. As a result, the genes that were passed down to you and everyone you know are the good ones that produced healthy and glowing skin, protected the body, and, most of all, attracted a mate. The bad skin genes that caused disease, weakened the individual, and turned off potential partners didn't get passed on and were eventually lost from the gene pool.

The way people look during the different stages of life fits in with this biological imperative. A baby's skin is soft and smooth to encourage its mother to care for it. During puberty, skin may look aggravated, angry, and out of sorts-which it is. But it's just adapting like the rest of the body to the surge of hormones and physical changes that transform children into adults. (This is, not surprisingly, little consolation to a teenager who suddenly develops terrible breakouts!)

From a biological point of view, the childbearing years are when skin really counts, as people who look their best are much more likely to attract a mate. Those with clear, radiant skin get the highest marks in the gene-pool competition, so it's no wonder that the skin's genetic program is designed to reach a crescendo of health and fitness during the courtship and reproduction years. In most cases, skin in the twenties and early thirties doesn't require much more than cleansing, moisturizing, and daily protection from the sun. Remember, these are the years that generations of human evolution have selected for maximum health with minimum maintenance.

Skin genes controlling shape and texture are not the only determining factor of who beds down with whom, of course, but during the mating ritual, they provide, often unconsciously and in a single glance, an enormous amount of information. A man looking at a woman will make instant judgments about her overall health, fitness, and the degree to which she possesses the "it" factor known as sex appeal. At the same time, a woman is also gathering vital information from her instant judgment about a man's looks. This was proven by a recent study at the University of California, Santa Barbara, which found that women can identify those men with higher testosterone levels and select those with high paternal quality and those who especially like infants just by looking at photographs of the men's faces.

Bottom line: Skin was built for sex. Skin health peaks during the reproductive years; after that, we need help.


THE SKIN YOU'RE IN
Your skin is a whole lot more than an inert overcoat, or something you might think of as cellular Saran wrap. It's a living thing-the largest organ of your body and one that changes dynamically over the course of your lifetime.
Like most organs, skin has two main layers: the dermis, the thick layer on the bottom; and the epidermis, the thin layer of cells on the surface above.

The living dermis is mainly comprised of cells called fibroblasts. These fibroblasts are surrounded by collagen and elastin fibers to form the stretchy supporting structure of the skin. The dermis is also infused with blood vessels to supply nutrients and take away waste, as well as nerves for exquisitely delicate sensation. Hair and oil and sweat glands are all anchored in the dermis and poke or wind their way out to the surface.

Perched on top of the dermis is the epidermis, a layer no more than about twenty cells deep. The cells making up this layer are called keratinocytes. They divide rapidly, but they only grow up, never down. As a result, whenever a keratinocyte divides, the newer cell is always on top. Think of this process as if the bottom cells are the grandmothers, and they divide into daughter cells that in turn divide into a new generation of daughter cells. All this continual division pushes the daughters, the granddaughters, and great-granddaughters up to the surface. It takes about two weeks for newly created daughter cells to be pushed to the surface, where they're sloughed off.

The very outermost layers of skin are stacked atop one another like shingles on a roof. After all the daughter cells finish dividing and reach the top of the skin surface, they flatten out, creating an intercellular cement mixture where ceramides and other lipids connect them to one another. Ceramides are lipids, a type of oil chemical. Each ceramide molecule has two ends, and each end can bind to other chemicals so that a long chain, or mesh, is formed. This network of mesh is what binds the flattened cells together to become the part of the outer skin barrier known as the stratum corneum.

The stratum corneum is basically dead skin cells, but it still serves an extremely vital function: preventing water from escaping from the skin. Without the barrier of the stratum corneum, essential water would evaporate from your body like steam from a boiling kettle, and you would dry up like a raisin in a few hours. The stratum corneum barrier also keeps out invaders, like deadly bacteria and viruses. The barrier function of the stratum corneum is literally a matter of life and death.

During the entire process of forming the dermis, epidermis, and stratum corneum, skin cells undergo a remarkable, genetically programmed transformation. Our genetic code, which exists in our DNA, tells our cells what to do. This is the DNA program.

The DNA program is like a computer program-a series of instructions about what to do and when to do it, intended to be performed in an orderly fashion. A person's DNA program tells a cell when to make things or how to act, as well as how to change what it is doing as it gets older or how to react when it gets information from other cells.

As in a computer program, if a DNA instruction is changed, the cell behaves differently. If the cell gets signals from damaged skin, or by the inevitable aging process itself, it can follow a new course of steps that are harmful to the skin. However, if we introduce special ingredients that give out new signals, we can reprogram the cell to change its course of development and change its function. This transformation, which is directed by information coded in the human genome, is the key to the New Skin-Care Revolution.

Bottom line: The skin has several parts and is constantly changing under the direction of its DNA program.


HOW SKIN CHANGES AS YOU AGE
Until now, aging was pretty much a steady downhill slide. Each month past those prime childbearing years seemed to add a new wrinkle and furrow, a little more drooping and sagging, strange new blotches and uneven tone, and more than a smattering of dark spots that can no longer be thought of as cute little freckles. Before you blame your parents or too frequent beach vacations, realize that both are culprits, because there are two basic ways the skin ages: intrinsic and extrinsic.

Intrinsic aging is driven by the genetic code, and up until now this has been pretty much out of your control. Intrinsic aging follows a specific process:


• The outer barrier weakens
• DNA repair lessens
• Blood flow declines
• Collagen degrades
• Chronic inflammation flares


Further, the underlying fat that gives us such delicious chubby cheeks as children is absorbed, so faces look more gaunt, the bones thin, and the muscles supporting the skin weaken. Then gravity takes over and jowls form, lips thin, cheekbones jut out, earlobes sag,...