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, noses seem to grow longer, and tiny blood vessels suddenly appear on the skin's surface. Extrinsic aging is caused by factors you can control. This includes the devastating effects of the sun upon skin, called photoaging. Photoaging is without question the largest extrinsic factor affecting your skin, causing it to get thick, rough, wrinkled, mottled, flaky, saggy, and covered with spots and uneven pigmentation. I can tell people till I'm blue in the face that there's no such thing as a healthy tan-but getting them to act like it is another issue altogether! Photoaging is the easiest extrinsic factor you can control, and it's never too late to start protecting your skin from the sun. How to protect yourself from photoaging and the effects of the sun is so crucial that I've devoted an entire chapter to it. Chapter 6 is a primer on photoaging, sunscreen and sun protection, and DNA repair and is without doubt the most important chapter in the book. Other extrinsic factors are smoking, poor nutrition, stress, not getting enough sleep, and in general taking your skin for granted. The temptation is to play today and pay tomorrow, but it's never too early to start protecting your skin-now. Bottom line: Aging is caused by both your genes and your behavior. AGING IN THE CHILDBEARING YEARS Of all the stages of life, the childbearing years put the greatest strain on the body and the skin. Once a woman has reached the peak of her health and attractiveness, she is now subjected to the toughest challenge of all-preparing for and giving birth to children. During this time, sensitivity to sun and irritants increases just as the damage accumulated from the childhood years begins to appear. On top of that, in the thirties, the production of skin lipids begins to decline, weakening the skin barrier. The childbearing years usually find women in their healthy prime, but it is during this time, when a woman seems to need it least, that the biggest gains can be made in fighting aging. A little understanding of the changes driven by genes and hormones can help any woman preserve her most youthful looks. For women in their twenties and thirties, many problems related to dryness, irritation, and acne are caused by hormonal changes during their monthly cycle. In the weeks prior to menstruation, the skin's barrier is the weakest and sun sensitivity is the greatest, so extra care should be taken to moisturize, wear sunscreen, and reduce sun exposure. During and after her period, a woman's skin is the most dry and the most sensitive, which calls for careful cleansing (see chapter 4) as well as continued moisturizing with a product containing an anti-irritating, calming agent (see chapter 5). Pregnancy causes a massive surge in the hormones estrogen and progesterone and can cause visible and often embarrassing changes in the skin. These usually come in the form of dark spots, acne, and/or discolored patches, a form of hyperpigmentation called chloasma, or "the mask of pregnancy," which usually fades after childbirth (a range of brightening and lightening options, covered in chapter 8, can help). Stretch marks may appear, a result of the distension and contraction of pregnancy that leave the abdominal muscles weak and skin paper thin. Add to that the irregular sleep, exhaustion, and the stresses of parenting, and a mother's good looks are never so challenged. Bottom line: The childbearing years are when you look your best and also when your skin faces its greatest challenges. CHANGE IN MIDDLE AGE After the age of thirty-five and into the forties is an ideal time for a woman to find a serious skin protection and reprogramming regimen that will slow aging to a crawl. This is where the products from the New Skin-Care Revolution can have their greatest benefit. Even though we are living longer and with healthier bodies than ever before, and even though enormous social changes have led to many people no longer being defined by age but by their stage in life, DNA just doesn't care. You might be forty-six and look thirty, but you can't fool your DNA. So even if at forty-six you've just run your twentieth marathon, your peak reproductive years are long gone, and the genetic program dictating changes in your skin has begun to run out of code. Around the age of forty, our DNA instructions for renewing and rejuvenating our skin essentially stop. The pressure for survival is at its peak during the childbearing years, so as far as our DNA is concerned, once we've successfully produced the next generation, our job is done. Evolution just hasn't kept up with the social changes and improvement in medical care and nutrition that allow so many of us to live decades longer than human beings once did. As a result, your cells' ability to repair DNA damage begins to diminish sometime in the twenties, and by the time you reach age seventy about half of this defense system is lost. In addition, during the thirties, the skin gradually loses its barrier function. This begins when the production of ceramides is reduced. Ceramides, remember, are those essential oils that hold the stratum corneum layer together like glue. Fewer ceramides means a reduction in the stratum corneum's strength. (By the age of sixty, ceramides have been so depleted that a third of the skin's barrier defense has been lost.) During your forties, your skin changes dramatically. The decline in DNA repair paves the way for collagen breakdown and the first deep wrinkles. Those days of unprotected sunning now show up as flaky patches and spots that are either overpigmented or underpigmented. Couple that with reduced estrogen levels as menopause approaches, which in turn diminishes collagen, diminishing skin's strength, and there's not only a weakening of the outer innate defenses against toxins from the environment, but also a compromising of the foundation of underlying collagen and elastin. The result? Fine lines, wrinkles, sags, creases, and less elasticity. While all this is going on, your skin is also losing about 35 percent of its antioxidant vitamin reservoir. The enzymes that initiate inflammatory responses begin to increase, and the blood flow to the skin declines. This means that the skin becomes more sensitive, cooler to the touch, blotchy, and more easily irritated and inflamed. Like it or not, by the time you hit forty, skin health is as big an issue as skin beauty. Ignore it at your peril! Bottom Line: Aging begins to appear in the forties when the genetic program has run out of instructions, and skin is left without a regeneration program. THE YOUNG OLD More and more people are living well beyond the official age that senior discounts and Social Security kick in. In fact, those in the sixty-five to seventy-four age group now constitute such a clear-cut new contingent that they are being called the "young old." Women who are over the age of sixty today are the lost beauty generation-the last generation to come of age before the era of the New Skin-Care Revolution. Of course, many mature women who practiced safe sun, used Retin-A early on, or inherited hardworking anti-aging genes have retained their clear, buoyant complexions. But for the most part, these women have skin that's been left to its own devices. If you're over sixty and you feel that you've missed the boat, there's good news-you haven't! Excerpted from The New Science of Perfect Skin: Understanding Skin-Care Myths and Miracles for Radiant Skin at Any Age by Daniel B. Yarosh All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.