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FOH Fact Sheets
Antioxidants and Cancer Prevention
Antioxidants protect cells from damage caused by unstable molecules known as free radicals (see Question 1&3).
Laboratory and animal research has shown antioxidants help prevent the free radical damage that is associated with cancer. However, results from recent studies in people (clinical trials) are not consistent (see Question 2).
Antioxidants are provided by a healthy diet that includes a variety of fruits and vegetables (see Question 4).
Choose one activity from the list of moderate or vigorous activities above and get started for a healthier you! Get a pencil and write your answer below. My goal is to (write one favorite activity here) for at least (minutes per day) minutes (number of times) times each week.
What are antioxidants?
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 otherwise might cause. Examples of antioxidants include beta-carotene, lycopene, vitamins C, E, and A, and other substances.
Can antioxidants prevent cancer?
Considerable laboratory evidence from chemical, cell culture, and animal studies indicates that antioxidants may slow or possibly prevent the development of cancer. However, information from recent clinical trials is less clear. In recent years, large-scale, randomized clinical trials reached inconsistent conclusions.
What was shown in previously published large-scale clinical trials?
Five large-scale clinical trials published in the 1990s reached differing conclusions about the effect of antioxidants on cancer. The studies examined the effect of beta-carotene and other antioxidants on cancer in different patient groups. However, beta-carotene appeared to have different effects depending upon the patient population. The conclusions of each study are summarized below.
Are antioxidants under investigation in current large-scale clinical trials?
Three large-scale clinical trials continue to investigate the effect of antioxidants on cancer. The objective of each of these studies is described below. More information about clinical trails can be obtained using cancer.gov/clinicaltrials, www.clinicaltrials.gov, or the CRISP database at www.nih.gov.
Will NCI continue to investigate the effect of beta-carotene on cancer?
Given the unexpected results of ATBC and CARET, and the finding of no effect of beta-carotene in the PHS and WHS, NCI will follow the people who participated in these studies and will examine the long-term health effects of beta-carotene supplements. The NCI established an Antioxidant Trialists' Collaborative Group to conduct a systematic meta-analysis of these results and to continue follow-up in all completed trials. Post-trial follow-up has already been funded by NCI for CARET, ATBC, the Chinese Cancer Prevention Study, and the two smaller trials of skin cancer and colon polyps. The Antioxidant Trialists' Collaborative Group may begin to complete follow-up studies on beta-carotene findings as early as May 2003.
How might antioxidants prevent cancer?
Antioxidants neutralize free radicals as the natural by-product of normal cell processes. Free radicals are molecules with incomplete electron shells which make them more chemically reactive than those with complete electron shells. Exposure to various environmental factors, including tobacco smoke and radiation, can also lead to free radical formation. In humans, the most common form of free radicals is oxygen. When an oxygen molecule (O2) becomes electrically charged or "radicalized" it tries to steal electrons from other molecules, causing damage to the DNA and other molecules. Over time, such damage may become irreversible and lead to disease including cancer. Antioxidants are often described as "mopping up" free radicals, meaning they neutralize the electrical charge and prevent the free radical from taking electrons from other molecules.
Which foods are rich in antioxidants?
Antioxidants are abundant in fruits and vegetables, as well as in other foods including nuts, grains and some meats, poultry and fish. The list below describes food sources of common antioxidants.
This information is from the National Institutes of Health.
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