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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 vegetables and fruits
their color. The body uses some types of carotenoids (but not lycopene)
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; macular degenerative disease, an age-related illness that can
lead to blindness; and lipid oxidation, the damage to normal fat
molecules that can cause inflammation and disease. It is also said to
lower 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 prevention and
treatment of cancers of the lung, prostate, stomach, bladder, cervix,
skin, and, especially, prostate. In support of these claims regarding
cancer, proponents note that lycopene is a powerful antioxidant, a
compound that blocks the action of free radicals, activated oxygen
molecules that can damage cells, and that several scientific studies
have found lower risk of cancer among people who eat lycopene-rich
foods.
What does it involve?
Tomatoes are the most concentrated food source of lycopene,
although apricots, guava, watermelon, papaya, and pink grapefruit are
also significant sources. Studies that looked at lycopene levels in the
blood found that levels were higher after people ate cooked tomatoes
than after they ate raw tomatoes or drank tomato juice. This suggests
that lycopene in cooked tomato products such as tomato sauce or paste
may be more readily absorbed by the body than lycopene in raw tomatoes.
Eating lycopene-rich vegetables and fruits together with a small amount
of oil or fat (for example, salad oil or cheese on pizza) increases the
amount of lycopene absorbed by the intestines. Lycopene is also
available in 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 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?
Population-based studies in many countries have shown that the
risk for some types of cancer is lower in people who have diets high in
tomato products or who have higher levels of lycopene in their blood.
Studies suggest that diets rich in tomatoes may account for this
reduction in risk. Evidence is strongest for lycopene's protective
effect against cancer of the lung, stomach, and prostate. It may also
help to protect against cancer of the cervix, breast, mouth, pancreas,
esophagus, and colon and rectum.
Some population studies have found that a diet high in
lycopene from tomato-based foods was linked with a lower risk of
prostate cancer. Other studies, however, found no link between tomato
products or other lycopene-rich foods and prostate cancer. A recent
study suggested that variation in a particular gene (known as XRCC1)
that helps repair damaged DNA influences whether lycopene intake will
affect a man's prostate cancer risk.
Since tomatoes also contain vitamins, potassium, and other
carotenoids and antioxidants, it is possible that other compounds in
tomatoes, either alone or in combination 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 their findings can be
explained by other factors that were not examined.
A 2004 review that analyzed 21 observational studies (that is,
not clinical trials) concluded that tomato products appear to have a
weak protective effect against prostate cancer. This review did not
include lycopene supplements, 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. On the other hand, 2 studies from 2007,
one of about 1,500 men and the second of more than 28,000 men, found no
difference in blood lycopene levels between those in whom prostate
cancer later developed and those in whom it did not.
There have been several 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 frequent intake of lycopene over a long period of
time considerably suppressed breast tumor growth in mice. However,
breast cancer in humans is very different from breast cancer in mice,
and those results may not apply to the disease in humans. In laboratory
studies, lycopene has also been shown to interfere with the growth of
many different types of human cancer cells growing in test tubes or
petri dishes, especially those that grow in response to insulin-like
growth factor I. Laboratory and animal studies can suggest possible
helpful effects, but they do not provide proof that such effects can be
achieved in humans. Further studies are needed to find out if possible
anti-cancer properties could benefit 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 received no special
supplements.
Results from a few controlled studies on the effects of
lycopene in humans have been published recently, but more clinical
information (including results of several studies already under way)
will be needed to determine whether lycopene-rich foods can be helpful
in preventing or treating cancer. All of the clinical trials completed
so far have reported relatively short-term effects on the level of
prostate-specific antigen (PSA) in the blood, which is generally
considered a good indicator of prostate cancer growth. Although these
studies are an important step, they are not as valuable as long-term
studies that determine whether a treatment actually helps patients live
longer or relieves their symptoms.
One study assigned men at high risk for prostate cancer to
take an ordinary multivitamin either with or without a lycopene
supplement and found no difference in PSA levels between the 2 groups.
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 with men whose
prostate cancer had stopped responding to hormone therapy found that
lycopene did not have a significant effect. One short-term study from
2006 reported that lycopene supplements were safe, but that they did
not lower the levels of prostate-specific antigen (a marker of prostate
cancer) in men with recurrent prostate cancer. Another reported that
the combination of lycopene and soy supplements prevented PSA levels
from increasing in some men with prostate cancer.
The American Cancer Society's nutrition guidelines recommend
eating a balanced diet that includes 5 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 likely to be healthier than
consuming large amounts of one particular food. Based on currently
available evidence, diet is likely to play a greater role in preventing
cancer than in treating it.
Are there any possible problems or
complications?
This product is sold as a
dietary supplement in the United States. Unlike drugs (which must be
tested before being allowed to be sold), the companies that make
supplements are not required to prove to the Food and Drug
Administration that their supplements are safe or effective, as long as
they don't claim the supplements can prevent, treat, or cure any
specific disease.
Some such products may not
contain the amount of the herb or substance that is written on the
label, and some may include other substances (contaminants). Actual
amounts per dose may vary between brands or even between different
batches of the same brand.
Most such
supplements have not been tested to find out if they interact with
medicines, foods, or other herbs and supplements. Even though some
reports of interactions and harmful effects may be published, full
studies of interactions and effects are not often available. Because of
these limitations, any information on ill effects and interactions
below should be considered incomplete.
Lycopene obtained from eating fruits and vegetables has no
known side effects and is thought to be safe for humans. The potential
side effects of lycopene supplements are not fully known. Patients in
one study who took a lycopene-rich tomato supplement of 15 milligrams
twice a day had some intestinal side effects such as nausea, vomiting,
diarrhea, indigestion, gas, and bloating. When consumed over a long
period of time, very large amounts of tomato products can give the skin
an orange color.
Supplements containing antioxidants such as lycopene may
interfere with radiation therapy and chemotherapy if taken during
cancer treatment. Even though studies have not been done in humans,
antioxidants are known to clean up free radicals, which could interfere
with one of the methods by which chemotherapy and radiation destroy
cancer cells. Eating fruits and vegetables high in antioxidants is
still considered safe during cancer treatment.
Relying on this type of treatment alone and avoiding or
delaying conventional medical care for cancer may have serious health
consequences.
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 found on
our Web site (www.cancer.org)
or ordered from our toll-free number (1-800-ACS-2345).
References
American Dietetic Association. Lycopene: an Antioxidant for
Good Health. Accessed at:
http://www.eatright.org/cps/rde/xchg/ada/hs.xsl/nutrition_5328_ENU_HTML.htm
on June 10, 2008.
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.
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. The 2006 Nutrition,
Physical Activity and Cancer Survivorship Advisory Committee. American
Cancer Society. 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.
Lawenda BD, Kelly KM, Ladas EJ, Sagar SM, Vickers A, Blumberg
JB. Should supplemental antioxidant administration be avoided during
chemotherapy and radiation therapy? J Natl Cancer Inst.
2008;100:773-783.
National Cancer Institute. Promises and perils of
lycopene/tomato supplementation and cancer prevention. (Executive
summary of February 17-18, 2005 conference) Accessed at:
http://dceg.cancer.gov/pdfs/davis1352014s2005.pdf on June 10, 2008.
Norrish AE, Jackson RT, Sharpe SJ, Skeaff CM. Prostate cancer
and dietary carotenoids. Am
J Epidemiol. 2000;151:119-123.
Paiva SA, Russell RM. Beta-carotene and other carotenoids as
antioxidants. J Am Coll
Nutr. 1999;18:426-433.
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.
Vaishampayan U, Hussain M, Banerjee M, Seren S, Sarkar FH,
Fontana J, Forman JD, Cher ML, Powell I, Pontes JE, Kucuk O. Lycopene
and soy isoflavones in the treatment of prostate cancer. Nutr Cancer.
2007;59:1-7.
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.
Last Medical Review: 11/01/2008
Last Revised: 11/01/2008
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