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Lycopene

Other common name(s): Rhodopurpurin

Scientific/medical name(s): none

Description

Lycopene is an antioxidant compound that gives tomatoes and certain other fruits and vegetables their color. It is one of the major carotenoids in the diet of North Americans and Europeans. (Carotenoids are pigments that give yellow, red, and orange colors to vegetables and fruits. The body can use some of these to make vitamin A.)

Overview

People who have diets rich in tomatoes, which contain lycopene, appear to have a lower risk of certain types of cancer, especially cancers of the prostate, lung, and stomach. Further research is needed to find out what role, if any, lycopene has in the prevention or treatment of cancer. It is likely that the preventive effect of diets high in fruits and vegetables cannot be explained by just one single part of the diet.

How is it promoted for use?

Proponents claim that lycopene may lower the risk of heart disease (hardening of the arteries of the heart), macular degenerative disease (an age-related illness which can lead to blindness), and lipid oxidation (damage to normal fat molecules that can then cause inflammation and disease). It is also said to lower low-density lipoprotein (LDL, or "bad") cholesterol, enhance the body's defenses, and protect enzymes, DNA, and cellular fats. A major claim for lycopene’s benefits is in the treatment of cancers of the lung, prostate, stomach, bladder, cervix, and skin.

Some researchers believe lycopene may be valuable in preventing and slowing the growth of cancers of the prostate, lung, and stomach. These scientists describe lycopene as a powerful antioxidant, a compound that blocks the action of activated oxygen molecules-- known as free radicals-- that can damage cells. The antioxidant activity of lycopene is at least twice as great as beta carotene, another carotenoid that is also thought to be an effective cancer-preventing nutrient (see Vitamin A and Beta Carotene). Lycopene is considered one of the more effective antioxidants because it is not converted to vitamin A after it is eaten. Conversion to vitamin A weakens the antioxidant properties of carotenoids like beta carotene.

What does it involve?

Dietary lycopene is mainly found in tomatoes, although apricots, guava, watermelon, papaya, and pink grapefruit are also significant sources. Tomatoes are the best food source of lycopene. Studies that looked at lycopene levels in the blood found that they were higher after people ate cooked tomatoes than if they ate raw tomatoes or drank tomato juice. This suggests that tomato sauce or paste may be a better source of available lycopene than raw tomatoes. Lycopene is also available in the form of soft-gel capsule supplements. Dosages vary according to manufacturer.

What is the history behind it?

In recent years, the role of the diet in preventing cancer has been a popular and important area of research. The examination of the role of other carotenoids, specifically beta carotene, in preventing cancer began in the 1920s. However, interest in lycopene did not really begin until the late 1980s when it was found that the antioxidant activity of lycopene was twice that of beta carotene.

What is the evidence?

Observing large groups from many countries has shown that the risk of developing some cancers is lower in people who either have diets high in tomato products or have higher levels of lycopene in their blood. Studies suggest that diets rich in tomatoes may account for this reduction in the risk of several different types of cancer. The strongest evidence is for a protective effect against cancers of the lung, stomach, and prostate gland. There may also be a protective benefit against cancers of the cervix, breast, mouth, pancreas, esophagus, colon, and rectum.

Some studies that observed large groups of people have found that a diet high in lycopene from tomato-based foods was linked with a lower in risk for prostate cancer. Other studies, however, found no link between tomato products and prostate cancer. A recent study suggested that variation in a particular gene (known as XRCC1, which helps repair DNA damage) influences whether lycopene intake will influence a man's prostate cancer risk.

Since tomatoes also contain vitamins, potassium, carotenoids, and other antioxidants, other compounds in tomatoes, either acting alone or with lycopene, may be responsible for some of the protective effects attributed to lycopene in some studies. When researchers look at large groups with different lifestyles and habits, it is also possible that the effect can be explained by other factors that were not examined.

A 2004 review that analyzed 11 observational and 10 case control studies concluded that tomato products appear to have a weak protective effect in preventing prostate cancer. This analysis did not involve lycopene supplements, but only tomato and tomato-based foods. Some of the individual studies, however, did consider lycopene levels in the blood. The analysis noted that the protective effect was slightly stronger for cooked tomato products, and that small amounts of added fat improved lycopene absorption.

There have been a few experimental studies on the role of lycopene in preventing or treating cancer. One animal study found that lycopene treatment reduced the growth of brain tumors. Another animal study showed that chronic intake of lycopene considerably suppressed breast tumor growth. This study may not apply to human disease, since 95% of human breast cancers are different than breast cancers in mice.

Lycopene has also been shown to interfere with the growth of many different human cancer cell lines in the laboratory, especially those that grow in response to insulin-like growth factor I. While animal and laboratory studies may show a certain substance holds promise as a cancer treatment, further studies are needed to learn whether the results apply to humans.

To test whether lycopene is the main cancer-fighting substance in tomatoes, one animal study compared lycopene supplements to powdered tomatoes. Groups of rats who were fed tomato powder were compared to rats given lycopene. The rats that received tomato powder had much lower cancer risk, whereas the rats receiving lycopene supplements did not differ significantly from the group that had no special supplements.

To look at cancer treatment, a controlled study in a small group of men with prostate cancer found that lycopene supplements appeared to reduce the rapid growth of prostate cancer cells. However, a more recent study found no significant effect on men with prostate cancer who had failed hormone therapy. These kinds of studies are just starting, and controlled studies in large groups of people will be needed to learn whether lycopene has a helpful effect in treating cancer. A number of smaller studies are now underway to look at tomato products and lycopene to find out if they are helpful in treating people with cancer.

One short-term study from 2006 reported that lycopene supplements were safe, but that they did not lower prostate specific antigen levels (a marker of prostate cancer) in men with recurrent prostate cancer. A 2007 study of more than 28,000 men found no difference in blood lycopene levels between men who later developed prostate cancer and those who did not.

The American Cancer Society's nutrition guidelines recommend eating a balanced diet that includes five or more servings a day of vegetables and fruit, choosing whole grains over processed and refined foods, and limiting red meats and animal fats. Choosing foods from a variety of fruits, vegetables and other plant sources such as nuts, seeds, whole grain cereals, and beans is healthier than consuming large amounts of one particular food.

Are there any possible problems or complications?

Lycopene obtained from eating fruits and vegetables has no known side effects and is thought to be safe for humans who are not allergic to the foods. The potential side effects of lycopene supplements are not fully known. Patients in one study who received a lycopene-rich tomato supplement of 15 milligrams (mg) twice a day had some intestinal side effects such as nausea, vomiting, diarrhea, indigestion, gas, and bloating. Very large amounts of tomato products taken over a long period of time can give the skin an orange color.

Antioxidant supplements may interfere with the killing of cancer cells if taken during chemotherapy or radiation treatment. Studies in humans are still needed to find out more about this. However, patients who are in cancer treatment should consult with a knowledgeable physician before taking vitamins, minerals, or other supplements. However, eating fruits and vegetables high in antioxidants is still considered safe during cancer treatment.

Additional Resources

More Information From Your American Cancer Society

The following information on complementary and alternative therapies may also be helpful to you. These materials may be ordered from our toll-free number (1-800-ACS-2345).

References

American Dietetic Association. Lycopene: an Antioxidant for Good Health. Available at: http://www.eatright.org/cps/rde/xchg/ada/hs.xsl/nutrition_5328_ENU_HTML.htm. Accessed June 14, 2007.

Boileau TW, Liao Z, Kim S, et al. Prostate carcinogenesis in N-methyl-Nitrosourea (NMU)-testosterone-treated rats fed tomato powder, lycopene, or energy-restricted diets. J Natl Cancer Inst. 2003; 95:1578-1586.

Campbell JK, Canene-Adams K, Lindshield BL, Boileau TW, Clinton SK, Erdman JW Jr. Tomato phytochemicals and prostate cancer risk. J Nutr. 2004; 134:3486S-3492S.

Clinton SK. Lycopene: chemistry, biology, and implications for human health and disease. Nutr Rev. 1998;56:35-51.

Clark PE, Hall MC, Borden LS Jr, et al. Phase I-II prospective dose-escalating trial of lycopene in patients with biochemical relapse of prostate cancer after definitive local therapy. Urology.2006;67:1257-1261.

Doyle C, Kushi LH, Byers T, et al. Nutrition and physical activity during and after cancer treatment: an American Cancer Society guide for informed choices. CA: a Cancer Journal for Clinicians. 2006;56:323-353.

Etminan M, Takkouche B, Caamano-Isorna F. The role of tomato products and lycopene in the prevention of prostate cancer: a meta-analysis of observational studies. Cancer Epidemiol Biomarkers Prev. 2004;13:340-345.

Gerster H. The potential role of lycopene for human health. J Am Coll Nutr. 1997;16:109-126.

Giovannucci E. Tomatoes, tomato-based products, lycopene, and cancer: review of the epidemiologic literature. J Natl Cancer Inst. 1999;91:317-331.

Goodman M, Bostick RM, Ward KC, et al. Lycopene intake and prostate cancer risk: effect modification by plasma antioxidants and the XRCC1 genotype. Nutrition & Cancer.2006;55:13-20.

Jatoi A, Burch P, Hillman D, et al. A tomato-based, lycopene-containing intervention for androgen-independent prostate cancer: results of a Phase II study from the North Central Cancer Treatment Group. Urology. 2007;69:289-294.

Kirsh VA, Mayne ST, Peters U, et al. A prospective study of lycopene and tomato product intake and risk of prostate cancer. Cancer Epidemiology, Biomarkers & Prevention. 2006;15:92-98.

Kushi LH, Byers T, Doyle C, et al. American Cancer Society guidelines on nutrition and physical activity for cancer prevention: reducing the risk of cancer with healthy food choices and physical activity. CA: a Cancer Journal for Clinicians. 2006;56:254-281.

Labriola D, Livinston R. Possible interactions between dietary antioxidants and chemotherapy. Oncology.1999;13:1003-1011.

Nagasawa H, Mitamura T, Sakamoto S, Yamamoto K. Effects of lycopene on spontaneous mammary tumour development in SHN virgin mice. Anticancer Res. 1995;15:1173-1178.

National Cancer Institute. Promises and perils of lycopene/tomato supplementation and cancer prevention. (Executive summary of February 17-18, 2005 conference) Available at: http://dceg.cancer.gov/pdfs/davis1352014s2005.pdf. Accessed June 14, 2007.

Norrish AE, Jackson RT, Sharpe SJ, Skeaff CM. Prostate cancer and dietary carotenoids. Am J Epidemiol. 2000;151:119-123.

Peters U, Leitzmann MF, Chatterjee N, et al. Serum Lycopene, Other Carotenoids, and Prostate Cancer Risk: a Nested Case-Control Study in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Cancer Epidemiol Biomarkers Prev. 2007 16: 962-968.

Paiva SA, Russell RM. Beta-carotene and other carotenoids as antioxidants. J Am Coll Nutr. 1999;18:426-433.

Porrini M, Riso P. Lymphocyte lycopene concentration and DNA protection from oxidative damage is increased in women after a short period of tomato consumption. J Nutr. 2000;130:189-192.

Rao AV, Agarwal S. Bioavailability and in vivo antioxidant properties of lycopene from tomato products and their possible role in the prevention of cancer. Nutr Cancer. 1998;31:199-203.

Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.

Revised: 07/12/2007

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