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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 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
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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.
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Gerster H. The potential role of lycopene for human health. J Am Coll Nutr.
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Giovannucci E. Tomatoes, tomato-based products, lycopene, and
cancer: review of the epidemiologic literature. J Natl Cancer Inst.
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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,
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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:
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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
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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
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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
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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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