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The Sunscreen ParadoxPopular Misconceptions About Skin Cancer Prevention

June 2006

By Steven V. Joyal, MD

The Best Skin-Protecting Topical Ingredients

Exciting recent research shows that, in addition to broad-spectrum UV-A and UV-B blocking ingredients, natural topical ingredients can help protect skin against free radical-generated damage induced by UV light. Such natural agents may offer protection against photoaging, hyperpigmentation, and skin cancers.

Retin-A® and Other Cancer-Preventive Strategies

Retin-A® (tretinoin), or trans-retinoic acid, was introduced more than 30 years ago as a highly successful acne treatment. It is currently available by prescription.

Topical tretinoin use may be very useful for people who are predisposed to developing skin cancer—such as those with a light complexion, a history of heavy sun exposure, or past basal or squamous cell skin cancer—since retinoids prevent tumor progression, a process known as chemoprevention.

In addition, in people with severe photodamage from the sun, the combination of nightly tretinoin and twice-daily topical application of the chemotherapeutic agent 5-fluorouracil (Efudex® or Fluoroplex®) is an effective anti-cancer regimen.23

Retin-A® can be quite irritating to the skin, particularly early in a treatment regimen. A 0.05% emollient cream formulation (Renova®) is currently available and is less irritating than 0.05% Retin-A® cream. Another new form is Retin-A Micro®, with “microsponges” that allow slow, metered release to reduce irritation.

• Green tea extract (epigallocatechin gallate, or EGCG). Deriving the health benefits of green tea is not limited to drinking it or taking it in the form of a high-potency extract. Topical administration likewise provides great benefits, including protecting against damage that can contribute to skin cancer and skin aging.

EGCG, a prime component of green tea, provides broad-spectrum protection against UV light-induced DNA damage and immune system dysfunction of the skin.24,25 Topical green tea extract is exceptional in preventing the inflammation and oxidative stress associated with UV light-induced skin damage.26-31 As a result, scientists believe green tea may help prevent skin cancers that commonly result from exposure to the sun’s radiation.

Exciting data from validated models of skin cancer strongly suggest that topically applied green tea extract can reduce the incidence and size of skin tumors. Importantly, this protection occurred even when green tea was applied following (not just before) UV light-induced damage.32 Thus, green tea may not only help prevent damage from UV rays, but also may help repair damage that has already occurred.

EGCG’s benefits also include anti-aging effects. In aging human skin, topically applied green tea extract stimulates structural support cells in the skin called keratinocytes, leading to an increase in skin thickness. Furthermore, subsequent UV exposure fails to destroy these cells, suggesting that topical green tea provides a protective effect against UV light.33 Thus, green tea helps reverse two of the hallmarks of aging skin: reduced skin thickness and keratinocyte destruction. This suggests a central role for green tea in preventing skin aging and promoting youthful skin.

Rosemary (Rosmarinus officinalis)

Rosemary extract (ursolic and carnosic acids). The aromatic herb rosemary, used for thousands of years as both a spice and medicinal agent, is particularly rich in carnosic and ursolic acids, two potent antioxidant and anti-inflammatory agents. More than a decade ago, scientists found that carnosic and ursolic acids effectively prevent skin cancer in a validated model of human skin cancer carcinogenesis.34

Ursolic acid acts powerfully to inhibit the growth of cancerous melanoma cells.35 It also inhibits reactive oxygen species in skin cells and prevents damage from the skin-aging effects of UV-A light.36

In addition, research has demonstrated that when specially formulated with lipids, ursolic acid enhances the dermal collagen and ceramide content of normal human skin cells, which are called epidermal keratinocytes.37,38 Collagen provides the “skeleton” that gives shape and structure to the skin, while ceramide is a lipid that helps maintain proper immune function, as well as youthful moisture content, in the skin. Keratinocytes make up as much as 95% of epidermal tissues and are responsible for producing keratin, the tough protein that contributes to healthy hair, nails, and skin.

Turmeric (Curcuma longa)

Turmeric extract (tetrahydrocurcumin). Curcumin is fast becoming known as a cure-all nutrient, and for good reason. Derived from the pungent spice turmeric, curcumin has excellent anti-inflammatory and antioxidant properties. Curcumin inhibits cancer initiation and promotion in validated cancer models.39,40

Curcumin induces the powerful tumor suppressor gene p53 and promotes the death of basal cell skin cancer cells.41 Furthermore, research shows that curcumin can make mutant, treatment-resistant malignant melanoma cell lines more responsive to chemotherapy.42

While these and other studies suggest that topical curcumin may benefit the skin, the staining properties of its bright yellow native pigment have prevented its widespread use in topical products. Fortunately, a major metabolite of curcumin called tetrahydrocurcumin does not possess the staining characteristics of native curcumin, yet it demonstrates anti-cancer effects that are similar to those of native curcumin. In fact, validated skin cancer models have shown that tetrahydrocurcumin inhibits skin cancer promotion.43

Laboratory studies indicate that topical tetrahydrocurcumin is a safe and effective skin-lightening agent.44,45 Skin-lightening agents help fade sun-induced areas of hyperpigmentation, or skin darkening. Many such agents work by inhibiting tyrosinase, a key enzyme involved in melanin synthesis. Thus, the colorless turmeric root derivative tetra-hydrocurcumin may help protect the skin against the detrimental effects of UV light and may help prevent (or fade) hyperpigmented areas of skin. While hyperpigmentation is not a medically harmful condition, it is always advisable to have a physician examine new brown spots to rule out skin cancers.

Milk thistle extract (silibinin). The milk thistle plant contains silibinin and silymarin, two compounds that are well known for their anti-oxidant, anti-inflammatory, and immune-enhancing properties in the context of liver disease. Less well known—but equally important—are the documented benefits of milk thistle extract against skin cancer.

Topical application of silymarin significantly decreased skin cancer number and size in a validated model of tumor promotion.46 These findings are supported by other studies that show similar effects for silibinin. For example, silibinin protects against UV light-induced DNA damage and cancer cell growth.47

Additionally, research shows that silibinin enhances the powerful tumor suppressor gene p53, a genetic factor that protects against cancer. Silibinin acts by other mechanisms to prevent UV light-induced skin cancer. In fact, some findings suggest that silibinin can help to repair DNA damage caused by previous exposure to UV light.48

Since milk thistle extract is well tolerated and acts in several ways to fight the cancer-causing effects of solar radiation, leading researchers believe it may be an ideal addition to sunscreen formulations.49

Licorice (Glycyrrhiza glabra)

Licorice root. The medicinal properties of licorice root have been known since ancient Greece and Rome.50 A powerful skin protectant, licorice has anti-inflammatory, immune-boosting, and anti-cancer effects, including protecting against DNA damage.51 Licorice extract also has demonstrated efficacy in treating atopic dermatitis, an allergy-related, intensely itchy swelling of the skin.52

Glycyrrhizin, the main component of licorice root, protects against UV-B light-induced damage in the context of human melanoma cells.53 Glycyrrhetinic acid, another constituent of licorice, protects against skin tumor initiation and promotion in a validated model of skin cancer.54

An extract of licorice called glabridin reduces inflammation resulting from UV light exposure. In fact, when a licorice extract rich in glabridin was applied to the skin before exposure to UV light, it helped prevent the redness and pigmentation that would normally have occurred. Licorice extract also reduces melanin synthesis, suggesting that it may have applications in preventing and fading unsightly “age spots,” or areas of hyper-pigmented skin.55

Furthermore, licorice extract’s antioxidant activity has been shown to enhance the stability of other compounds when added to a topical dermatological cream.56


The FDA’s sun protection factor (SPF) rating system is inherently flawed in that it measures the effectiveness of sunscreen products against UV-B light, but not against deeper-penetrating UV-A light. Unfortunately, despite the FDA’s public acknowledgment of this shortcoming back in 2000, the rating system has still not been changed.

Natural sunlight activates vitamin D in the skin, and vitamin D has extraordinary anti-cancer benefits. For those at greatest risk of skin cancer, consuming additional vitamin D may be a more appropriate strategy than additional sun exposure. Although there are many unusual theories about skin cancer in the medical literature, until these theories have more definitive proof, a cautious approach to sun exposure is indicated. For most of us, a prudent strategy suggests 10-15 minutes of exposure to natural sunlight two to three times weekly, with additional vitamin D supplementation as a reasonable option.

Natural topical products such as green tea extract, turmeric, and licorice root extract offer remarkable protection against premature skin aging and skin cancer that all too often result from excessive sun exposure and sunburn.

Your skin is designed to last a lifetime—treat it well, and it will!


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