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Skin Aging
INTRODUCTION
Skin is the largest organ of the human body, weighing approximately 10 pounds and covering an area of about 16 square feet. We generally take skin for granted and tend not to take very good care of it. Our skin is responsible for protecting our internal organs from the toxic external world. Our skin protects us from heat, cold, and physical injuries. It also provides us with sensory information about the nature of the external world and is our first defense against invasion by bacteria, viruses, and other toxic elements. The skin is also an excretory organ, removing toxins from the body via perspiration.
Although there are many diseases that can affect the skin, the most common problems that we all have are the effects of our exposure to ultraviolet (UV) radiation from the sun over time. Having a healthy tan has, in the past, been a sign of good health. In the last 10 years, with the changes in the ozone layer in the upper atmosphere, it is clear that the effects of UV radiation from the sun are much more dangerous than originally thought. There are many causes for the accumulated cellular damage in the skin that we call aging. Among these are the oxidative processes and related free radical damage that result from UV sunlight, smog, toxins, cigarette smoke, X-rays, drugs, and other stressors. Young skin is also exposed to these potentially damaging changes, but when we are young, there is sufficient cellular energy (ATP) for DNA repair and cell renewal. Enzymes that provide antioxidant activity such as SOD and catalase are readily available. As we age, there is increased wear and tear, while at the same time the energy for cell repair and renewal is diminished and the antioxidant enzymes are less available.
Specific diseases that affect the skin will not be covered in this protocol, but will rather be listed under the disease category itself (e.g., Acne). This protocol will primarily deal with the effects of aging on the skin.
Health-conscious Americans are concerned about the damage that sunlight inflicts on the skin. Protecting against the effects of ultraviolet radiation is a multi-million dollar industry. Creams, lotions, cosmetic products, and protectants are to be found everywhere, resulting in confusion for the consumer regarding what products are really helpful. Cosmetic companies may seize upon an idea, put that ingredient into a cream or lotion without much research, and then advertise it to an unsuspecting public. This protocol will only use evidence from peer-reviewed journals.
The Anatomy of Our Skin
Our skin consists of two main layers: the dermis and epidermis. The dermis is the inner layer of skin that contains nerve fibers, fat cells, blood vessels, sweat and oil glands, and hair follicles. The dermis also contains collagen and elastin, two proteins that are responsible for the structure and elasticity of the skin itself. These proteins are subject to the process of aging. The sweat and oil glands in the dermis protect the outer layer of skin with a thin coating of oil and perspiration.
The epidermis is the outermost layer of our skin. New cells generated by the dermis continually replace this layer. Removal of the epidermis, as in a scrape or burn, reveals an unprotected sensitive dermis underneath. The epidermis also contains melanocytes or pigment cells. These cells produce melanin, which determines the shade of your skin (a heritable factor).
SKIN AND FREE RADICALS
Scientists now believe that the free radical theory of disease also applies to the aging of the skin. Free radicals are unstable small molecules generated by an oxygen environment which require stabilization by the body's antioxidant system. Free radicals occur throughout every cell in our body simply by virtue of the fact that oxygen is our principal metabolic fuel. Strong sunlight readily generates free radicals in the skin. Our hands, face, neck, and arms are the areas usually chronically exposed to light. These parts of the body, particularly the face, are where aging of the skin shows up.
The skin protein collagen is particularly susceptible to free radical damage, and when this damage occurs, it causes the collagen protein molecules to break down and then link back up again in a different way; this is known as cross-linking. Collagen cross-linking causes the normally mobile collagen to become stiff and less mobile. Sunlight also causes the messenger molecules present in skin cells to become active and create inflammatory products. Fisher et al. (1977) have shown that the multiple small exposures to ultraviolet irradiation lead to sustained elevations of enzymes that degrade skin collagen and contribute to photo- aging.
Skin cancer typically occurs in skin that is photo-aged. Wrinkles, laxity, uneven pigmentation, brown spots, and a leathery appearance characterize photo-aged skin. In contrast, chronologically aged skin that has been protected from the sun is thin and has reduced elasticity, but is otherwise smooth and unblemished.
The following factors can accelerate skin aging:
- sun exposure
- first- or secondhand cigarette smoke
- environmental toxins
- poor diet
- excess alcohol consumption
- stress
- harsh soaps or detergent-based moisturizers
- sleep deprivation
One way of mitigating the effects of these skin-damaging foes is to increase levels of protective antioxidants through a diet rich in fruits and vegetables or by direct topical application.
Critics used to claim there was no evidence that topically based products affected skin aging. Over the years, a remarkable number of published studies have proven these skeptics wrong! Science clearly substantiates the role that free radicals play in causing skin aging and the fact that topically applied antioxidants confer significant protection and can even partially reverse some aspects of skin aging. Indeed, various animal and human studies have proven that low molecular weight antioxidants, especially vitamins C and E, as well as alpha-lipoic acid exert protective effects against free radical damage (oxidative stress) (Podda et al. 2001).
In a double-blind study, a topical vitamin C complex was applied to one half of the face and a placebo gel to the opposite side. Clinical evaluation of wrinkling, pigmentation, inflammation, and hydration was performed prior to the study at weeks 4, 8, and 12. The results showed a statistically significant improvement of the vitamin C-treated side, with decreased photoaging scores of the cheeks and the perioral area. The peri-orbital area improved in both the vitamin C and placebo-gel group, probably indicating improved hydration. The overall facial improvement of the vitamin C side was statistically significant. Biopsies showed increased collagen formation in the vitamin C group. This study showed that topically applied vitamin C results in clinically visible and statistically significant improvement in wrinkling when used for 12 weeks. This clinical improvement correlated with biopsy evidence of new collagen formation (Fitzpatrick et al. 2002).
In response, cosmetic companies have increased the percentages of active ingredients with the goal of replicating the antiaging effects revealed in the published studies. The problem of increasing the level of active ingredients is that the wrong layers of the skin can be overly saturated resulting in irritation and reduced efficacy.
The first step in resolving this problem is to encase the active ingredients so that they can be absorbed through the top layer into the lower layers of the skin where they are most active. The second step is to design a delayed release system so that the active ingredients can be released over an extended amount of time.
Other Factors
In spite of the effect of sunlight on the skin, there are other factors that affect skin health that occur regardless of our exposure to sun rays. Dryness, loss of tone and fullness, diminished immune responses, and reduced ability to repair damage are all factors that contribute to the aging process.
There are many types of skin tones and qualities. Men tend to have thicker skin than women due to the dominant hormone testosterone. However, in later years, the lack of estrogen in women and testosterone in men tend to cause changes in both genders.
Each individual will have a different skin, with different oil production, color, and texture. Clearly, people with dry, white skin should use only mild cleansers and never use grainy cleansing products. Moisturizers and oil-based make-ups will also be required. On the other hand, those with an oily, darker skin can use mild liquid cleansers and an oil-blotting foundation. Generally, the use of sunscreens is reasonable as long as it does not create a false sense of security. Do not go out for longer periods of time in the sun just because you're wearing a sunscreen.
Skin damage occurs when the membrane covering of the skin cell is damaged by free radicals. Free radicals make the membrane more permeable, allowing the cells to dehydrate (lose water). The membrane of the cell is what is called a lipid bilayer: two layers of fat end-on-end. Enzymes are activated when the skin is traumatized or exposed to sun. Enzymes break down the lipid bilayer and cause inflammation. Thus, any antioxidants must be fat-soluble to protect this layer.
Chronic inflammation is an underlying cause of common degenerative diseases. One study found that pro-oxidative factors that accelerate skin aging might activate a self-maintained micro-inflammatory process that interferes with skin elasticity and thickness. This study stated that topical antioxidants decrease this inflammatory cascade and thus afford protection to the skin structures (Giacomoni et al. 2000).
The effect of exposure to even ambient UV irradiation increases the risk for long-term, detrimental effects characterized by wrinkles and loss of skin tone and resilience. Photo-aged skin displays prominent alterations in the cellular component and the extracellular matrix of the connective tissue. UV exposure results in an accumulation of disorganized elastin and a severe loss of collagens, the major structural proteins of the dermal connective tissue. The unifying pathogenic agents for these changes are UV-generated free radicals. As well as causing permanent gene mutations, free radicals activate signal transduction pathways that are related to growth, differentiation, senescence, and connective tissue degradation (Scharfetter-kochanek et al. 2000).
WHAT IS GOOD FOR YOUR SKIN?
When most people think about good things that they can do for their skin, they usually think about things they will put on their skin rather than what they will put inside themselves to make their skin healthier. Although topical application of certain products is essential, equally important is the nourishment of the skin from the inside. Everything from essential fatty acids, antioxidants, and other supplements to the food that we eat is critical in maintaining healthy skin that ages slowly.
The Outside Story
The first preventive measure you can take is to reduce the amount of UV light that you are exposed to. This can be done either by avoiding the sun completely or more practically by wearing at least an SPF15 sunblock. One danger with using a sun block is that it tends to make people feel like they can go out in the sun more! So they end up with the same amount of UV radiation because they are simply out in the sun longer. For areas that are more exposed, such as the nose and cheekbones, a sun-blocking titanium oxide would probably be best.
Considerable interest has been generated about combining antioxidants with sunscreens to provide enhanced protection against UV rays. Two of the best-known antioxidants are vitamins C and E, both of which have been shown to be effective in different models of photodamage. In a study done on swine skin, vitamin C provided additive protection against acute UVB damage (sunburn cell formation) when combined with a UVB sunscreen. When a combination of vitamins E and C were used, very good protection from a UVB insult occurred. Vitamin C, however, was significantly better than vitamin E at protecting against a UVA-mediated phototoxic insult in this animal model (Darr et al. 1996).
When it comes to makeup and skin care products, people with oily skin should clearly avoid products that have oil in their formula. Those with dry skin need products that have essential oils combined in the formula. Cleansing the skin by washing once daily without astringent products is probably a good idea as well. Facial masks can help hydrate skin, but can be harmful if they cause irritation. They should never be used more than once a week.
Antioxidants
Although antioxidants are well-known for their beneficial effects inside the body when taken orally, in the case of skin, there are a number of antioxidants that are helpful when applied topically (Podda et al. 2001).
Human studies have demonstrated pronounced protective effects of antioxidants when applied topically before UV radiation exposure. With respect to UVB-induced skin damage, the photoprotective effects of antioxidants are significant. Topical application of such combinations may result in a sustained antioxidant capacity of the skin, possibly due to antioxidant synergisms. Free radicals are culprits behind UVA-induced skin alterations, thus indicating a basis for topical antioxidant administration. In a human study, topical application of antioxidants resulted in diminished severity of UVA-induced sun damage. Thus, regular application of skin care products containing antioxidants may be of the utmost benefit in efficiently preparing skin against exogenous oxidative stressors occurring during daily life. Sunscreen agents may also benefit from combination with antioxidants resulting in increased safety and efficacy of such photoprotective products (Dreher et al. 2001).
Vitamin C Esters. Vitamin C ester is vitamin C with a fatty acid attached to it. It is fat-soluble and rapidly penetrates the skin, being much better absorbed than vitamin C alone. Products containing vitamin C ester, such as ascorbyl palmitate, will be helpful in reducing and preventing skin damage (Yamamoto et al. 2002). |