|
Other common name(s):
none
Scientific/medical name(s):
Brassica oleracea italica
Description
Broccoli is a cruciferous vegetable that belongs to the
cabbage and mustard families, 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.
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 (see Vitamin
A and Beta Carotene, Folic
Acid, and Vitamin
C).
It is also the source of many phytochemicals (chemicals from plants)
that may have anti-cancer properties (see also Phytochemicals).
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 antioxidants and may boost
detoxifying enzymes in the body. Some studies have also suggested they
may alter body estrogen levels, 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, boiled, or steamed. 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 over 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 that diets high in
cruciferous vegetables (a group of plants that have 4 flowers
resembling a cross) seem to be linked to 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.
Raw broccoli's slightly bitter taste can be traced to the same
chemicals thought to provide cancer protection. As a result, scientists
have developed different types of broccoli, such as broccolini, a cross
between broccoli and Chinese kale, which looks like asparagus and
tastes sweeter than broccoli.
What is the evidence?
Diets high in cruciferous vegetables appear to be linked with
a lower risk of certain cancers. A study that looked at large groups of
people 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 cancers of the colon. A similar study suggested that
those who ate cruciferous vegetables seemed to have less bladder
cancer, but another study (in 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, people with certain
glutathione S-transferase types are less likely to develop lung cancer
if their intake of these vegetables is high. Randomized clinical trials
are needed to clarify these results.
Lab and animal studies have suggested that certain compounds in
broccoli may have anti-cancer properties. Animal and lab studies may
show a certain compound holds promise, but further studies are needed
to find out if the results apply to humans.
Some research has suggested that sulforaphane, which is present at much
higher levels in broccoli sprouts than in the mature vegetable, may be
a powerful cancer-preventing agent. The compound 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 lab animals that were fed
sulforaphane. Other studies in lab dishes have shown that sulforaphane
may help protect against prostate, colon, pancreas, and other cancers.
Some studies have also suggested that the compound may help treat some
cancers. 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 lab studies have shown it may slow or stop the growth of
breast, prostate, and other cancer cell lines. Some early studies in
animals have shown similar results. Small studies in humans have found
it may prevent the development of precancerous growths in the cervix,
as well as growths (papillomas) in the throat. Again, larger studies
are needed to find out what benefits against cancer I3C may have.
Scientists caution that as promising as broccoli may be as an excellent
food for preventing cancer, the results of 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's not clear whether the phytochemicals in broccoli, for
example, have benefit on their own. It is still unclear whether it is
the vitamin C, beta carotene, folate, or other compounds that, working
together and in the right quantities, 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?
Broccoli and broccoli sprouts are generally safe to eat.
Since it is a food 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 cause more
irritation, especially in those with certain bowel conditions.
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
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.
PDRhealth. Indole-3-Carbinol. Available at:
www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/ind_0315.shtml.
Accessed June 12, 2007.
PDRhealth. Sulforaphane. Available at:
www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/sul_0243.shtml.
Accessed June 12, 2007.
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.
Revised: 07/12/2007
|
