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Topics in Complementary and Alternative Therapies (PDQ®)

Nutritional Therapies

Antioxidants and Cancer Prevention

Antioxidants are substances that may protect cells from the damage caused by unstable molecules known as free radicals. Free radical damage may lead to cancer. Examples of antioxidants include beta-carotene, lycopene, vitamins C, E, and A, and other substances.

There has been some concern about whether antioxidants may make chemotherapy and radiation therapy less effective.

Coenzyme Q10

Coenzyme Q10 is made naturally by the human body. Coenzyme Q10 helps cells produce energy and acts as an antioxidant. Studies show that coenzyme Q10 may boost the immune system and protect the heart from damage caused by certain chemotherapy drugs. No report of a randomized clinical trial using coenzyme Q10 as a treatment for cancer has been published in a peer-reviewed scientific journal.

  • See the PDQ patient summary on Coenzyme Q10 for more information.

Dietary Supplements

Many studies suggest that the use of complementary and alternative medicine is common among prostate cancer patients, and the use of vitamins, supplements, and specific foods is frequently reported by these patients.

Gerson Therapy

The Gerson therapy is used by some practitioners as a treatment for cancer based on changes in diet and nutrient intake. An organic vegetarian diet plus nutritional and biological supplements, pancreatic enzymes, and coffee or other types of enemas are the main features of the Gerson therapy. Few clinical studies of the Gerson therapy have been published.

Gonzalez Regimen

The Gonzalez regimen is a cancer treatment that is tailored by the practitioner for each patient and is currently available only to the patients of its developer. It involves taking certain pancreatic enzymes thought to have anticancer activity. The regimen also includes specific diets, vitamin and mineral supplements, extracts of animal organs, and coffee enemas.


Lycopene is a carotenoid (a natural pigment made by plants). It is found in a number of fruits and vegetables, including apricots, guava, and watermelon. The main source of lycopene in the American diet is tomato-based products. Lycopene is thought to have antioxidant activity. Lycopene has been studied for its role in chronic diseases, including cardiovascular disease and cancer.


Melatonin is a hormone made by the pineal gland during the hours of darkness. It plays a major role in the sleep-wake cycle. Clinical studies in renal, breast, colon, lung, and brain cancer suggest that melatonin may make chemotherapy and radiation therapy more effective; however randomized, blinded trials are needed to study these results.

Modified Citrus Pectin

Citrus pectin is found in the peel and pulp of citrus fruits such as oranges, grapefruit, lemons, and limes. Citrus pectin can be modified with high pH and heat so that it can be digested and absorbed by the body. Modified citrus pectin (MCP) may have effects on cancer growth and metastasis. Some research suggests that MCP may be protective against various types of cancer, including colon, lung, and prostate cancer.


The pomegranate (Punica granatum L.) is native to Asia and grown in many parts of the world. Different parts of the pomegranate fruit have bioactive compounds that may support good health, including antioxidants found in the peel. Certain pomegranate extracts have been shown in laboratory studies to slow the growth and spread of prostate cancer cells and to cause cell death.


Probiotics are live microorganisms used as a dietary supplement to help with digestion and normal bowel function. A bacterium found in yogurt called Lactobacillus acidophilus is the most common probiotic. The use of probiotics may be recommended in conditions related to diarrhea, gut-barrier dysfunction, and inflammatory response.


Selenium is a trace mineral (a nutrient that is essential to humans in tiny amounts). Selenium is found in certain proteins that are active in many body functions, including reproduction and immunity. Selenium is being studied for its role in cancer.


Soy is from a plant native to Asia that grows beans used in many food products. Soy foods (e.g., soy milk, miso, tofu, and soy flour) contain phytochemicals that may have health benefits. Isoflavones are the most widely researched compounds in soy. Soy is being studied for the prevention of cancer, hot flashes during menopause, and osteoporosis (loss of bone density).


Tea has long been thought to have health benefits, and many believe it can help lower the risk of cancer. Tea contains polyphenol compounds including catechins, which are antioxidants that help protect cells from damage caused by free radicals.

Some studies suggest that green tea may have a protective effect against cardiovascular disease. There is also evidence that green tea may protect against various forms of cancer.

Vitamin C, High-Dose

Vitamin C (ascorbic acid) is a nutrient that humans must get from food or supplements since it cannot be made in the body. Vitamin C is an antioxidant and helps prevent oxidative stress. It also works with enzymes to play a key role in making collagen. High-dose vitamin C has been studied as a treatment for cancer patients.

Vitamin D

Vitamin D is a nutrient involved in a number of functions that are essential for good health. Skin exposed to sunshine can make Vitamin D. It can also be consumed in the diet, but very few foods naturally contain vitamin D. These foods include fatty fish, fish liver oil, and eggs.

Vitamin E

Vitamin E is a nutrient that the body needs in small amounts to stay healthy and work the way it should. It is fat-soluble (can dissolve in fats and oils) and is found in seeds, nuts, leafy green vegetables, and vegetable oils. Vitamin E boosts the immune system and helps keep blood clots from forming. It also helps prevent cell damage caused by free radicals (unstable molecules in the body). Vitamin E is being studied in the prevention and treatment of some types of cancer. It is a type of antioxidant.

  • Updated: April 2, 2015