Lycopene is a carotenoid found in grapefruit, watermelons, and papaya in addition to tomatoes. It is obtained only through diet. Lycopene exhibits antioxidant and anticancer properties.
Results from several epidemiologic studies suggest a strong association between high intake of lycopene-rich foods and reduced risk of several cancers, notably prostate cancer. However, few well designed clinical trials have been conducted, and data remain inconclusive.
Because lycopene supplementation is associated with strong antioxidant effects, it has the potential to interfere with chemotherapy and radiation therapy. Cancer patients should use caution if considering an increase in their lycopene intake.
—Barrie Cassileth, PhD
ALSO KNOWN AS: Nonprovitamin A carotenoid
SUMMARY: Lycopene is a carotenoid found in tomatoes, grapefruit, watermelons, and papaya. It is also synthesized by plants and microorganisms, but cannot be synthesized by the human body and can only be obtained via diet. Lycopene as a dietary supplement is a potent antioxidant used to help prevent cancer, heart disease, and macular degeneration. It is classified as a nonprovitamin A carotenoid because it cannot be converted to vitamin A.
A few studies have suggested benefits of lycopene for exercise-induced asthma and benign prostatic hyperplasia. Data from epidemiologic studies indicate an inverse relationship between dietary and supplemental lycopene consumption and risk of cancers, particularly prostate, lung, and stomach cancers, as well as estrogen receptor (ER)- and progesterone receptor (PR)-positive breast cancers. Furthermore, low intake of tomato sauce was associated with advanced prostate cancer in patients with low-grade cancer at diagnosis. A few randomized clinical trials have been conducted to determine the role of lycopene in prostate cancer with mixed results. Well designed studies are warranted.
Proposed mechanisms of action in cancer prevention include inhibition of cancer growth, induction of differentiation by modulation of cell-cycle regulatory proteins, alterations in insulin-like growth factor–1 or vascular endothelial growth factor levels, prevention of oxidative DNA damage, and possible enhancement of carcinogen-metabolizing enzymes.
ADVERSE REACTIONS: No adverse effects have been reported at normal doses of lycopene. Chronic ingestion of large quantities of lycopene-rich foods, such as tomato products, can cause lycopenodermia, characterized by deep orange discoloration of the skin. A possible interaction between lycopene and alcohol consumption was reported, indicating that cytochrome P450 (CYP) 2E1 expression is induced by high doses of lycopene and alcohol.
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For additional information, visit the Memorial Sloan-Kettering Cancer Center Integrative Medicine Service website, “About Herbs,” at http://www.mskcc.org/AboutHerbs.