Natural Cancer Prevention

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Every fourth Saturday afternoon, Ben and Joan Page set aside an hour for just the two of them.

The hour isn’t spent on a planned romantic encounter, nor is it a scheduled time to talk. Rather, they spend the hour helping each other check for signs of skin cancer.

Sound far-fetched? It shouldn’t, considering that skin cancer is the most common form of cancer and one of the most curable, if detected early enough. According to the American Cancer Society, about 800,000 people had some form of skin cancer last year, and nearly 10,000 people died from it.

The monthly routine of Ben and Joan Page (not their real names)–to check for signs of skin cancer–is one of the best ways to keep the disease from spreading out of control, according to the cancer society. But in addition to keeping an eye on things, you can do even more by taking some preventive steps.

To date, the only unequivocal way to decrease the risk of skin cancer is to avoid overexposure to the sun and to avoid industrial chemicals such as arsenic. Further, researchers are exploring promising phytochemicals found in herbs, vegetables, and fruits that may help prevent and/or slow the disease. Most of the phyto­medicines described here are contained in foods that can be safely added to your diet now, if you don’t already include them in your favorite recipes or take them in supplement form. But because the research on these phytochemicals is in the early stages, and because individuals have their own sets of sensitivities and health concerns, it’s best to query your health-care provider to see whether adding any of these natural medicines to your diet is right for you.

Turmeric, a common spice used in making curries, contains the yellow pigment curcumin, which is both an antioxidant and an anti-inflammatory. (For more information, see “Turmeric: The favorite of ancients wins scientific acclaim” on page 39 of the November/December 1996 issue of Herbs for Health.) Animal studies suggest that curcumin may also be effective in preventing skin cancer.

In a study at Rutgers University reported in 1997, topical administration of an ­alcohol extract of curcumin prevented ­tumors in mice with skin cancer, both ­before and after exposure to a cancer-causing agent. In other studies, animals were fed curcumin. Researchers found that the curcumin inhibited squamous cell cancer. Scientists believe that curcumin staves off the development of skin cancer because it ­affects the enzymes that metabolize carcinogens in such a way that they become less toxic. This confirms earlier studies which showed that topical administration of curcumin effectively decreased chemically ­induced skin cancer in mice. When curcumin was taken orally, squamous cell ­carcinomas of the mouth decreased.

Because of the strong early evidence in such animal studies–and the fact that the scientific community accepts that curcumin has no toxic side effects–the ­National Cancer Institute is considering human trials to test curcumin as a preventive agent for a variety of tumors, including skin cancer.

Garlic (Allium sativum)

Several extensive studies on humans have shown that eating garlic is associated with decreased levels of mammary and colon cancers. Garlic may also provide a potent cancer-fighting topical preparation: In a 1992 study, the oil-­soluble portion of garlic was applied to mice with cancer, and the cancer receded. Research on this topical preparation continues.

An added benefit to garlic is that it contains agents that can stimulate repair of damaged DNA, making this herb a potent protector against cancer.

Milk thistle (Silybum marianum)

Milk thistle is most widely known for its ability to protect the liver. (For more information about milk thistle, see “Milk thistle therapy” on page 46 of the July/ August 1997 issue of Herbs for Health.) But researchers are discovering another asset to this herb–it contains a compound that may also prevent skin cancer.

Milk thistle contains a strong antioxidant known as silymarin, which has been shown to inhibit the characteristic DNA damage caused by sunlight. A 1997 animal study showed that silymarin inhibited skin cancer induced by ultraviolet light; an animal study conducted by the same authors in 1994 showed that silymarin can inhibit chemically induced cancers as well. In the first study, the antioxidant also decreased the amount of sunburn and swelling on skin that had been exposed to ultraviolet light.


Retinoic acid has been used to treat a ­variety of cancers and skin diseases, including acne, but its use in treating and preventing skin cancer is still contro­versial because studies offer different conclusions.

Recent laboratory tests have indicated that retinoids, vitamin A derivatives, may play a preventive role in skin cancer. However, two large human trials showed that taking retinoids every day reduced the incidence of squamous cell skin cancer for people at low risk for it, but not for those at high risk. The retinoids did not decrease basal-cell skin cancer.

Because of these findings, some scientists are beginning to believe that a ­variety of retinoids and carotenoids is needed to prevent cancer, rather than just retinol alone. Animal studies have consistently shown that carotenoids can prevent skin cancer.

Herbs that contain a variety of both carotenoids and retinoids include dandelion (Taraxacum officinale), stinging nettle (Urtica dioica) or other nettle species, and violet (Viola odorata).

Green and Black tea (Camellia sinensis)

Both green and black tea contain antioxidants. Many studies have shown that extracts from green tea can decrease both the number and size of skin tumors in mice that were exposed to ultraviolet light, cancer-causing chemicals, or both. In other animal studies, green tea extracts affected enzymes involved in the metabolism of carcinogens in such a way that it decreased the carcinogens’ activity.

In one 1997 study at Rutgers University, mice were given tea for one week before they were exposed to cancer-causing ultraviolet light. The animals continued to drink the tea daily for forty-five weeks; during this time they were also exposed to the ultraviolet light twice a week. After forty-five weeks, researchers found that animals drinking either green or black tea had 53 percent to 65 percent fewer tumors per mouse than mice not receiving tea. Not only did the number of tumors per mouse decrease, but the size of the tumors also decreased in the groups receiving tea.

But when decaffeinated tea was used, the results weren’t as promising. Researchers speculate that caffeine may be one of tea’s cancer-fighting agents, although how it works and whether it works with other constituents in black and green tea to fight cancer is still being investigated.

Additionally, when green or black tea was administered directly to the animals’ skin twice a week for four weeks after exposure to ultraviolet light, skin-tumor formation decreased. Decaffeinated tea wasn’t used in this experiment.

Green tea has also been shown to reduce DNA damage caused by ultraviolet light. Researchers believe that, in addition to being able to directly decrease the amount of carcinogen that binds to DNA, tea phytochemicals act as antioxidants and enhance the activity of enzymes responsible for detoxification of carcinogens. A recent study from the Medical College of Ohio showed that one of the phytochemicals in tea could inhibit an enzyme associated with the spread of tumors, so researchers think that tea may also help decrease the spread of cancer. Studies of large groups of people show that drinking one cup to six cups of tea daily can decrease the incidence of several types of cancer. But be sure that your tea is not too hot, because the studies suggest that drinking very hot tea may contribute to esophageal cancer.


This compound found in grapes, mulberries, and peanuts shows early evidence of inhibiting several phases of skin cancer. In a 1997 study at the University of Illinois at Chicago, researchers applied resveratrol to the skin of mice and found that it inhibited cancerous tumors caused by chemicals. Researchers know that resveratrol is both an antioxidant and an anti-inflammatory agent that can decrease carcinogens’ toxicity; this preliminary evidence should stimulate more research on the chemopreventive effects of resveratrol in humans. (For more information about resveratrol, see “Inside plants” on page 14 of the July/August 1997 issue of Herbs for Health).


Coumarins are a large class of various compounds found in lavender oil, sweet woodruff, and sweet clover. Coumarins have been used to prevent malignant melanomas from recurring in patients previously treated unsuccessfully for this cancer with other substances. A 1994 study from Japan showed that coumarin, taken orally, was effective in preventing the recurrence of malignant melanoma in patients previously diagnosed with the disease. Studies in Germany have produced similar results. During 1997, studies conducted in Japan showed that a coumarin found in citrus inhibits skin cancer in mice. In this experiment, the coumarin was applied to the skin, followed by a cancer-causing agent. Mice receiving the coumarin had 27 percent fewer tumors than those not receiving the treatment.

Although the preliminary results of these studies look promising, a cautious approach to coumarins should be taken because they are toxic–they can damage the liver and cause excess bleeding. Researchers believe they fight cancer by stimulating the immune system.

Researchers will continue to try to identify which herbs and dietary elements will prevent skin cancer in humans, and how much of each is an adequate preventive dose. Until more is known, though, it is generally considered safe to use the herbs and dietary elements described above as preventives, with a health-care provider’s guidance. Side effects are rare and will depend on the individual. If you experience discomfort when taking an herb or using it topically–say a skin rash develops–stop using the herb immediately because you may be allergic to it.

Skin cancer facts

The most common forms of skin ­cancer ­develop on sun-exposed areas.

Basal cell cancer develops in the lower level of the epidermis, and progresses more slowly than the other types of skin cancer. It focuses on invading and destroying surrounding tissues, rather than spreading out to other areas. If left untreated, it can cause extensive tissue damage.

Squamous cell cancer develops in the outer layer of the epidermis and is more likely to spread to lymph nodes and other parts of the body.

Malignant melanoma is a cancer of the skin’s pigment cells and usually appears as a mole with irregular color and shape. Malignant melanoma is the least common of the skin cancers, but it’s also the most dangerous because it grows rapidly and invades other tissues quickly.

Skin check

Early detection is one of the best defenses against skin cancer. If you find one of the following warning signs, consult your health-care provider:

• A small lesion on your trunk or limbs with an irregular border and red, white, blue, or blue-black spots

• Shiny, firm, pearl-colored or black bumps or lesions anywhere on the skin

• Dark lesions on the palms, the soles, or the tips of your fingers and toes

• Large brownish spot with darker speckles on skin exposed to sun

• Red-purple spots anywhere on the skin

• Purple-brown or dark blue nodules on your toes or legs

• Pearly or waxy bump on your face, ear, or neck

• Flat, flesh-colored or brown scarlike lesion on your chest or back

• Firm, red nodule or flat lesion with scaly or crusted surface on your face, ears, neck, hands, or arms

• Change in a mole or any sore that fails to heal

Tips on using preventive herbs

Although research on the herbs that may help prevent skin cancer is still preliminary, most researchers agree that the herbs under study and described in the accompanying article are generally considered safe to use under the guidance of a health-care provider. Side effects are rare, but any discomfort following use may signal that you are allergic to the substance and should stop using it.

A topical oil can be made with dried milk thistle, dandelion, violet, or green or black tea. Put a small amount of the herb into a jar, then cover the herb with almond oil, and let the mixture sit in a dark place for about two weeks. The oil will bring out the herb’s beneficial agents. The oil can be added to the bath or used as a skin softener after time in the sun or after a shower.

Some of these herbs come in pill, capsule, or tincture form, convenient ways to take them. Or, you can use garlic and turmeric to spice up an otherwise ordinary dish, and dandelion, stinging nettle, and violet–herbs high in vitamin A–to make a tasty tea. Or, of course, you can brew the more traditional green or black tea.

Cindy Jones holds a doctorate in biochemistry and molecular biology from the University of Cincinnati. She spent several years in oncology research at the University of Colorado Health Sciences Center in Denver. Currently, she is a medical writer, consultant, and educator living in western Colorado. She wrote “Allies in the breast cancer battle: Herbs for prevention, treatment, and healing” on page 28 of the January/February 1998 issue of Herbs for Health.

Additional reading

Boone, C. W., and L. W. Wattenberg. “Current strategies of cancer chemoprevention: 13th Sapporo cancer seminar.” Cancer Research 1994, 54:3315-3318.

Chemoprevention Branch and Agent Development Committee, Clinical Development Plan. “Tea extracts, green tea polyphenol, epigallocatechin gallate.” Journal of Cellular Biochemistry 1996, 26S:236-257.

Huang, M-T., et al. “Effects of tea, decaffeinated tea, and caffeine on UVB light-induced complete carcinogenesis in SKH-1 mice: Demonstration of caffeine as a biologically important constituent of tea.” Cancer Research 1997, 57:2623-2629.

Huang, M-T., et al. “Inhibitory effects of topical application of low doses of curcumin on 12-0-tetradecanoylphorbol-13-acetate-induced tu­mor promotion and oxidized DNA bases in mouse epidermis.” Carcinogenesis 1997, 18:1, 83-88.

Jang, M., et al. “Cancer chemopreventive activity of resveratrol, a natural product derived from grapes.” Science 1997, 275:218-220.

Katiyar, S. K., N. J. Korman, H. Mukhtar, and R. Agarwal. “Protective effects of silymarin against photocarcinogenesis in a mouse skin model.” Journal of the National Cancer Institute 1997, 89:556-565.

Moon, T. E., et al. “Retinoids in prevention of skin cancer.” Cancer Letters 1997, 19:203-205.

Rohlfs, D. C., et al. “Chemoprevention of chemically induced skin tumor development by ­diallyl sulfide and diallyl disulfide.” Pharmaceutical Research 1992, 9:1668-1670.

Tucker, M. A., et al. “Clinically recognized dysplastic nevi, a central risk factor for cutaneous melanoma.” The Journal of the American Medical Association 1997, 277:1439-1444.

Wang, Z. Y., et al. “Inhibitory effects of black tea, green tea, decaffeinated black tea, and decaffeinated green tea on ultraviolet B light-induced skin carcinogenesis in 7,12-dimethylbenz[a]anthracene-initiated SKH-1 mice.” Cancer ­Research 1994, 54:3428-3435.

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