National Institutes of Health • National Center for Complementary and Alternative Medicine
Cancer and CAM:
What the Science Says
CAM for Cancer Prevention
Although researchers continue to investigate the possible role of vitamin and mineral supplements in preventing cancer, available evidence does not support taking these supplements for this purpose:
- A 2007 review of clinical trials looking at the effectiveness of multivitamin/mineral supplements for cancer prevention found that few such trials have been conducted, and that the results of most large-scale trials have been mixed. According to the National Cancer Institute, the following supplements have been studied but have not been shown to lower the risk of cancer: vitamins B6, B12, E, and C; beta-carotene; folic acid; and selenium.
- Two large-scale studies—the Alpha-Tocopherol, Beta-Carotene (ATBC) Cancer Prevention Trial and the Beta-Carotene and Retinol Efficacy Trial (CARET)—found evidence that supplements containing beta-carotene increased the risk of lung cancer among smokers.
- An independent review of data from the Selenium and Vitamin E Cancer Prevention Trial (SELECT), funded by the National Cancer Institute, NCCAM, and other agencies at the National Institutes of Health (NIH), showed that selenium and vitamin E supplements, taken either alone or together, did not prevent prostate cancer.
- A 2003 Agency for Healthcare Research and Quality (AHRQ) review found little evidence of cancer prevention benefits from three antioxidants (vitamins C and E, and coenzyme Q10).
- A 2008 review of 20 clinical trials found no convincing evidence that antioxidant supplements prevent gastrointestinal cancer, but did find indications that some might actually increase overall mortality. The review looked at beta-carotene, selenium, and vitamins A, C, and E. Selenium alone demonstrated some preventive benefits.
- The National Cancer Institute notes research indicating that higher intake of calcium may be associated with reduced risk of colorectal cancer, but concludes that the available evidence does not support taking calcium supplements to prevent colorectal cancer.
A 2009 review of 51 studies with more than 1.6 million participants found "insufficient and conflicting" evidence regarding an association between green tea consumption and cancer prevention. Most of the research to date has consisted of epidemiological (observational) studies carried out in Asia, and the authors of the review point to the need for well-designed clinical trials to evaluate green tea—in liquid and capsule form—for cancer prevention.
Additional information on cancer prevention is available from the National Cancer Institute.
CAM for Cancer Treatment
Botanical supplements are among the most common CAM approaches used by cancer patients. A 2008 review of the research literature concluded that some botanicals used in Ayurvedic medicine and traditional Chinese medicine may have a role in cancer treatment. However, scientific evidence is limited—much of the research on botanicals and cancer treatment is in the early stages. The review also notes that botanicals can have side effects and can interact with cancer drugs, blood thinners and other prescription drugs, and each other.
It is unclear whether the use of vitamin and mineral supplements by people who have been diagnosed with cancer is beneficial or harmful. For example, taking a daily multivitamin might improve the nutritional status of patients who cannot eat a healthful diet, but there is concern that some supplements might interfere with cancer treatment or increase the risk of a recurrence. Related studies have been inconsistent or inconclusive. Additional, well-designed research is needed to investigate how use of vitamin and mineral supplements by people with cancer relates to treatment efficacy, recurrence, survival, and quality of life.
While some research has reported benefits from taking antioxidants for cancer, there is not enough scientific evidence to support their use by cancer patients. A 2003 AHRQ review of cancer-related research on three antioxidants (vitamins C and E, and coenzyme Q10) found little scientific evidence of cancer treatment benefits. Patients' use of antioxidants while undergoing chemotherapy or radiation therapy has not been well studied. However, a 2008 review of published research suggests that antioxidant supplements may decrease the effectiveness of chemotherapy and radiation therapy.
CAM for Cancer Symptoms and Side Effects
Studies have found acupuncture to be useful in managing chemotherapy-associated vomiting in some cancer patients. Although research on acupuncture for cancer pain control and for management of other cancer symptoms is limited, some studies have shown beneficial effects that warrant further investigation. A 2008 evidence-based review of clinical options for managing nausea and vomiting in cancer patients noted electroacupuncture as an option to be considered.
Various studies also suggest possible benefits of CAM therapies such as hypnosis, massage, meditation, and yoga in helping cancer patients manage side effects and symptoms of the disease. For example, a study of 380 patients with advanced cancer concluded that massage therapy may offer some immediate relief for these patients, and that simple touch therapy (placing both hands on specific body sites)—which can be provided by family members and volunteers—may also be helpful. The study was conducted at 15 hospices in the Population-based Palliative Care Research Network.
A 2008 review of the research literature on botanicals and cancer concluded that although several botanicals have shown promise for managing side effects and symptoms such as nausea and vomiting, pain, fatigue, and insomnia, the scientific evidence is limited (the reviewers did not find sufficient evidence to recommend any specific treatment), and many clinical trials have not been well designed. As with use for cancer treatment, use of botanicals for symptom management raises concerns about interactions with cancer drugs, other drugs, and other botanicals.
NCCAM Clinical Digest is a service of the National Center for Complementary and Alternative Medicine, NIH, DHHS. NCCAM Clinical Digest, a monthly e-newsletter, offers evidence-based information on CAM, including scientific literature searches, summaries of NCCAM-funded research, fact sheets for patients, and more.
The National Center for Complementary and Alternative Medicine is dedicated to exploring complementary and alternative healing practices in the context of rigorous science, training CAM researchers, and disseminating authoritative information to the public and professionals. For additional information, call NCCAM’s Clearinghouse toll-free at 1-888-644-6226, or visit the NCCAM Web site at nccam.nih.gov. NCCAM is 1 of 27 institutes and centers at the National Institutes of Health, the Federal focal point for medical research in the United States.
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