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Other common
name(s): none
Scientific/medical
name(s): Brassica oleracea italica
Description
Broccoli is a cruciferous vegetable that belongs to the
cabbage family, which also includes arugula, cauliflower, collards, bok
choy, kale, mustard greens, radishes, turnips, watercress, rutabaga,
and brussels sprouts. It is identified by its dense clusters of green
flower buds.
Overview
Broccoli contains certain chemicals that may reduce the risk
of colorectal or other cancers, although it is not clear which
individual compounds may be responsible for the protective effects.
While research in this area continues, the best advice at this time to
reduce cancer risk is to eat a wide variety of vegetables. It is
reasonable to include broccoli as part of a balanced diet.
How is it promoted for use?
Broccoli is considered a good source of nutrients because it
is rich in vitamin C, carotenoids (vitamin A-like substances), fiber,
calcium, and folate. Broccoli is also a source of many substances
called phytochemicals, or plant chemicals, that may have anticancer
properties. For example, broccoli contains several compounds called
isothiocyanates, including sulforaphane and indole-3-carbinol (I3C),
which have been touted as possible anti-cancer agents in recent years.
Early studies have shown these substances may act as anti-oxidants and
may boost detoxifying enzymes in the body. Some studies have also
suggested they may alter the levels of estrogen in the body, which
might affect breast cancer risk.
The chemical composition of broccoli and other cruciferous
vegetables is complex, which makes it hard to determine which compound
or combination of compounds may provide protection against cancer.
Eating a wide variety of plant-based foods may be the best way to get
the necessary components.
Some researchers suggest that small amounts of broccoli
sprouts may protect against the risk of cancer as effectively as much
larger amounts of the mature vegetable. We are not aware of any
clinical studies that have been done in humans to verify this claim.
What does it involve?
Broccoli can be eaten raw or cooked in a variety of ways. It
can be purchased fresh or frozen in most grocery and organic food
stores. Broccoli retains the most nutrients when eaten raw. Cooking
reduces some of the benefits of broccoli because the heating process
seems to destroy some anti-cancer compounds.
Some chemicals found in broccoli, such as indole-3-carbinol,
are also available in pill form as dietary supplements.
What is the history behind it?
Broccoli has been around for more than 2,000 years but has
only been commercially grown in the United States since the 1920s.
Today, more than 90% of the broccoli harvested in the United States
comes from California, although it is also grown in other parts of the
country.
About 2 decades ago, researchers first suggested a possible
link between diets high in cruciferous vegetables (a group of plants
including cauliflower, cabbage, broccoli, and Brussels sprouts)) and a
lower risk of cancer. However, it was not until the 1990s that certain
chemicals found in broccoli were identified as possible
cancer-preventing compounds. In 1997, a study was published that noted
broccoli sprouts had higher levels of one of these compounds than
mature broccoli.
What is the evidence?
Diets high in cruciferous vegetables appear to be linked with
a lower risk of certain types of cancer. A population-based study found
that those who ate diets high in lutein, a vitamin A–like
chemical obtained from vegetables such as broccoli, spinach, and
lettuce, had fewer cases of colon cancer. A similar study suggested
that those who ate cruciferous vegetables seemed to have a lower risk
for bladder cancer, but a similar study of smokers found no such
benefit. Recent studies suggest that the effect of broccoli and related
cruciferous vegetables on cancer risk may partly depend on an inherited
variation in certain metabolic enzymes. For example, when people with
certain glutathione S-transferase types eat a diet high in cruciferous
vegetables, their risk for lung cancer is lower. Randomized clinical
trials are needed to clarify these results.
Laboratory and animal studies have suggested that certain
compounds in broccoli may have anti-cancer properties. These types of
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 whether possible anticancer properties could benefit
humans. Some research has suggested that sulforaphane, a substance that
is present at much higher levels in broccoli sprouts than in the mature
vegetable, may be a powerful cancer-preventing agent. Some researchers
have suggested that eating small amounts of broccoli sprouts may
protect against the risk of cancer as effectively as much larger
amounts of the mature vegetable. We are not aware of any clinical
studies that have been done in humans to verify this claim.
Sulforaphane is thought to prompt the body to make higher levels of
enzymes that protect against cancer-causing chemicals. One study showed
that breast tumor development was significantly reduced in laboratory
animals that ate sulforaphane. Other laboratory studies have shown that
sulforaphane may help protect against prostate, colon, pancreas, and
other types of cancer. Some studies have also suggested that the
compound may help treat some types of cancer. More research in animals
and humans will be needed to confirm these findings.
Another substance in broccoli, indole-3-carbinol (I3C), seems
to alter estrogen levels and may also raise levels of protective
enzymes in the body. Several studies of cancer cells growing in
laboratory dishes or flasks have shown it may slow or stop the growth
of breast, prostate, and other cancer cells. Some early studies in
animals have shown similar results. Small studies in humans have found
it may prevent the development of pre-cancerous growths in the cervix,
as well as growths called papillomas in the throat. Again, larger
studies are needed to find out what benefits I3C may have against
cancer.
Scientists caution that while broccoli appears promising as an
excellent food for preventing cancer, the results of such studies
cannot be considered by themselves. The anti-cancer effects of any
single food cannot be completely understood without looking at it as
part of a bigger dietary picture. It is still unclear, for example,
whether the phytochemicals in broccoli have benefit on their own or
whether it is the vitamin C, beta carotene, folate, and other
compounds, working together and in the right quantities, that might
protect people against cancer.
A balanced diet that includes 5 or more servings a day of
fruits and vegetables along with foods from a variety of other plant
sources such as nuts, seeds, whole grain cereals, and beans is likely
to be more healthful than eating large amounts of one food.
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.
Broccoli and broccoli sprouts are generally safe to eat. Since
broccoli is high in fiber, eating large amounts of it may cause gas.
High-fiber foods should be reduced or avoided in people with diarrhea
and some other colon problems. Raw broccoli may be more likely to cause
irritation, especially in those with certain bowel conditions. Relying
on this type of diet 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
Bell MC, Crowley-Nowick P, Bradlow HL, et al.
Placebo-controlled trial of indole-3-carbinol in the treatment of CIN. Gynecol Oncol.
2000;78:123-129.
Brennan P, Hsu CC, Moullan N, et al. Effect of cruciferous
vegetables on lung cancer in patients stratified by genetic status: a
mendelian randomisation approach. Lancet.2005;366:1558-1560.
Cao G, Booth SL, Sadowski JA, Prior RL. Increases in human
plasma antioxidant capacity after consumption of controlled diets high
in fruit and vegetables. Am
J Clin Nutr. 1998;68:1081-1087.
Cover CM, Hsieh SJ, Tran SH, et al. Indole-3-carbinol inhibits
the expression of cyclin-dependent kinase-6 and induces a G1cell cycle
arrest of human breast cancer cells independent of estrogen receptor
signaling. J Biol Chem.
1998;273:3838-3847.
Fahey JW, Zhang Y, Talalay P. Broccoli sprouts: an
exceptionally rich source of inducers of enzymes that protect against
chemical carcinogens.
Proc Natl Acad Sci USA.1997;94:10367-10372.
Michaud DS, Pietinen P, Taylor PR, Virtanen M, Virtamo J,
Albanes D. Intakes of fruits and vegetables, carotenoids and vitamins
A, E, C in relation to the risk of bladder cancer in the ATBC cohort
study. Br J Cancer.
2002;87:960-965.
Michaud DS, Spiegelman D, Clinton SK, Rimm EB, Willett WC,
Giovannucci EL. Fruit and vegetable intake and incidence of bladder
cancer in a male prospective cohort. J Natl Cancer Inst.
1999;91:605-613.
Nestle M. Broccoli sprouts in cancer prevention. Nutr Rev.
1998;56:127-130.
Parnaud G, Li P, Cassar G, et al. Mechanism of
sulforaphane-induced cell cycle arrest and apoptosis in human colon
cancer cells. Nutr
Cancer. 2004;48:198-206.
Parnaud G, Li P, Cassar G, Rouimi P, Tulliez J, Combaret L,
Gamet-Payrastre L. Mechanism of sulforaphane-induced cell cycle arrest
and apoptosis in human colon cancer cells. Nutr Cancer.
2004;48:198-206.
PDRhealth. Indole-3-Carbinol. Accessed at:
www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/ind_0315.shtml
on Accessed June 10, 2008.
PDRhealth. Sulforaphane. Accessed at:
www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/sul_0243.shtml
on June 12, 2007. Content no longer available.
Shapiro TA, Fahey JW, Wade KL, Stephenson KK, Talalay P. Human
metabolism and excretion of cancer chemoprotective glucosinolates and
isothiocyanates of cruciferous vegetables. Cancer Epidemiol Biomarkers Prev.
1998;7:1091-1100.
Shapiro TA, Fahey JW, Dinkova-Kostova AT, et al. Safety,
tolerance, and metabolism of broccoli sprout glucosinolates and
isothiocyanates: a clinical phase I study. Nutrition & Cancer.
2006;55:53-62.
Singh SV, Srivastava SK, Choi S, et al. Sulforaphane-induced
cell death in human prostate cancer cells is initiated by reactive
oxygen species. J Biol
Chem. 2005;280:19911-19924.
Slattery ML, Benson J, Curtin K, Ma KN, Schaeffer D, Potter
JD. Carotenoids and colon cancer. Am
J Clin Nutr. 2000;71:575-582.
Tang L, Zhang Y, Jobson HE, et al. Potent activation of
mitochondria-mediated apoptosis and arrest in S and M phases of cancer
cells by a broccoli sprout extract. Molecular Cancer Therapeutics.2006;5:935-944.
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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