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. Antioxidants interact with and stabilize free radicals and may prevent some of the damage free radicals might otherwise cause. There has been some concern about whether antioxidants may decrease the effectiveness of chemotherapy and radiation therapy. Examples of antioxidants include beta-carotene; lycopene; vitamins C, E, and A; and other substances. Refer to the NCI Fact Sheet on Antioxidants and Cancer Prevention for more information about antioxidants.
Coenzyme Q10 is made naturally by the human body. Coenzyme Q10 helps cells to produce energy, and it acts as an antioxidant. Coenzyme Q10 has shown an ability to stimulate the immune system and to protect the heart from damage caused by certain chemotherapy drugs. No report of a randomized clinical trial of coenzyme Q10 as a treatment for cancer has been published in a peer-reviewed scientific journal. Refer to the PDQ summary on Coenzyme Q10 for more information.
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. Refer to the PDQ summary on Prostate Cancer, Nutrition, and Dietary Supplements for information about green tea, lycopene, modified citrus pectin (MCP), pomegranate, soy, and Zyflamend supplements used by some prostate cancer patients.
The Gerson therapy is advocated by its supporters as a method of treating cancer patients 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 are found in the medical literature. Refer to the PDQ summary on the Gerson Therapy for more information.
The Gonzalez regimen is a complex cancer treatment that is tailored by the practitioner for each specific patient and is currently available only to the patients of its developer. Pancreatic enzymes taken orally are the primary agents in the regimen thought to have direct antitumor effects. The regimen also includes specific diets, vitamin and mineral supplements, extracts of animal organs, and coffee enemas. Refer to the PDQ summary on the Gonzalez Regimen for more information.
Lycopene is a carotenoid found in a number of fruits and vegetables, including apricots, guava, and watermelon, but most of the lycopene consumed in the United States comes from tomato-based products. When ingested, lycopene is broken down into a number of metabolites and is thought to have various biological functions, including antioxidant capabilities. Lycopene has been investigated for its role in chronic diseases, including cardiovascular disease and cancer. Refer to the Lycopene section in the PDQ summary on Prostate Cancer, Nutrition, and Dietary Supplements for more information.
Melatonin is a hormone produced by the pineal gland during the hours of darkness, plays a major role in the sleep-wake cycle, and is linked to the circadian rhythm. Clinical studies in renal, breast, colon, lung, and brain cancer suggest that melatonin exerts anticancer effects in conjunction with chemotherapy and radiation therapy; however, evidence remains inconclusive. Refer to the Botanical/dietary supplements section in the PDQ summary on Sleep Disorders for information about how melatonin is being studied in sleep disturbances.
Modified Citrus Pectin
Citrus pectin is a complex polysaccharide found in the peel and pulp of citrus fruit and can be modified by treatment with high pH and temperature. MCP may have effects on cancer growth and metastasis through multiple potential mechanisms, as suggested in preclinical research. Some research suggests that MCP may be protective against various types of cancer, including colon, lung, and prostate cancer. Refer to the Modified Citrus Pectin section in the PDQ summary on Prostate Cancer, Nutrition, and Dietary Supplements for more information.
The pomegranate (Punica granatum L.) is native to Asia and cultivated widely throughout world. Various components of the pomegranate fruit contain bioactive compounds, including phenolics, flavonoids, and anthocyanins, some of which have antioxidant activity. Pomegranate extracts have been shown to inhibit the proliferation of human prostate cancer cells in vitro. Refer to the Pomegranate section in the PDQ summary on Prostate Cancer, Nutrition, and Dietary Supplements for more information.
Probiotics are nutritional supplements that contain a defined amount of viable microorganisms. The use of probiotic functional foods (beneficial live microorganisms) to modify gut microflora has been suggested for clinical conditions associated with diarrhea, gut-barrier dysfunction, and inflammatory response. Refer to the Management section in the PDQ summary on Gastrointestinal Complications for information about probiotics.
Selenium is an essential trace mineral involved in a number of biological processes, including enzyme regulation, gene expression, and immune function. Selenium is being studied for its role in cancer. Refer to the Selenium section in the PDQ summary on Prostate Cancer, Nutrition, and Dietary Supplements for information about studies investigating the effects of selenium on prostate cancer.
Soy comes from a plant of Asian origin that produces beans used in many food products. Soy foods (e.g., soy milk, miso, tofu, and soy flour) contain phytochemicals that may have health benefits and, among these, soy isoflavones have been the focus of most of the research. Soy is being studied for the prevention of cancer, hot flashes that occur with menopause, and osteoporosis (loss of bone density). Refer to the Soy section in the PDQ summary on Nutrition in Cancer Care for information about the use of soy in breast cancer patients. Refer to the Soy section in the PDQ summary on Prostate Cancer, Nutrition, and Dietary Supplements for information about studies investigating the effects of soy on prostate cancer.
Tea has long been regarded as an aid to good health, and many believe it can help reduce the risk of cancer. Tea contains polyphenol compounds, particularly catechins, which are antioxidants and whose biological activities may be relevant to cancer prevention. Refer to the NCI Fact Sheet on Tea and Cancer Prevention: Strengths and Limits of the Evidence for information about tea and cancer prevention.
Some observational and interventional studies suggest that green tea may have a protective effect against cardiovascular disease, and there is evidence that green tea may protect against various forms of cancer. Refer to the Green Tea section in the PDQ summary on Prostate Cancer, Nutrition, and Dietary Supplements for more information about studies investigating the effects of green tea on prostate cancer.
Vitamin C, High-Dose
Vitamin C (ascorbic acid) is an essential nutrient that has antioxidant functions, is a cofactor for several enzymes, and plays an important role in the synthesis of collagen. High-dose vitamin C has been studied as a treatment for cancer patients. Refer to the PDQ summary on High-Dose Vitamin C for more information.
Vitamin D is involved in a number of processes that are essential for good health. Vitamin D is produced by the body in response to sunlight exposure. It can also be obtained through the diet, but very few foods naturally contain vitamin D. These foods include fatty fish, fish liver oil, and eggs. Refer to the NCI Fact Sheet on Vitamin D and Cancer Prevention for information about scientific studies that have investigated the possible role of vitamin D in cancer prevention. Refer to the Vitamin D section in the PDQ summary on Prostate Cancer, Nutrition, and Dietary Supplements for information about studies investigating the effects of vitamin D on prostate cancer.
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 (highly reactive chemicals). Vitamin E is being studied in the prevention and treatment of some types of cancer. It is a type of antioxidant, also called alpha-tocopherol. Refer to the Vitamin E section in the PDQ summary on Prostate Cancer, Nutrition, and Dietary Supplements for information about studies investigating the effects of vitamin E on prostate cancer. Refer to the Herbs/dietary supplements section in the PDQ summary on Hot Flashes and Night Sweats for information about hot flashes and vitamin E studies.