Health Benefits of Cruciferous Vegetables

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Health Benefits of Cruciferous Vegetables

• Pennington Biomedical Research
  Center

Heli Roy, PhD Shanna Lundy,
BS Phillip Brantley, PhD, Director
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Cruciferous vegetablesWhat are they?

• The cruciferae are the family of plants that
  include the various familiar members of the
  species Brassica oleracea.
• Examples include Broccoli, cabbage, cauliflower,
  kale, Brussels sprouts in the US.
• Other examples widely consumed outside of the US
  include Oriental cabbage, arugula, watercress,
  radish, daikon, wassabi, and various mustards.

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• A striking and characteristic chemical property
  of cruciferous plants is their high content of
  glucosinolates.
• Glucosinolates and their isothiocyanate
  hydrolysis (breakdown) products are well-known
  protectors against carcinogenesis, suggesting
  that greater intakes of these vegetables may
  lower the risk of several types of cancer.

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The Unusual Phytochemistry of Crucifers

• Glucosinolates are the precursors of
  isothiocyanates (mustard oils).
• Glucosinolates play protective and evolutionarily
  important roles in plants, including
• Allelopathy
• Suppression of growth of neighboring plants
• Specific positive and negative feeding cues
• For some insects
• Broad antibiotic properties
• Including nematocidal, antimicrobial, antifungal,
  antiprotozoal, and
  insecticidal activities

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In humans?

• When food is prepared or chewed, or in response
  to plant injury by predators, the enzyme
  myrosinase which accompanies the glucosinolates
  is released.
• This is the enzyme responsible for hydrolyzing
  glucosinolates to isothiocynates.
• In the absence of myrosinase (when food is cooked
  and myrosinase is heat inactivated), humans have
  the ability to efficiently convert glucosinolates
  to isothiocynates through the action of
  microflora in the GI tract.

Cabbage worm
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Overview
Conversion of Glucosinolates to Isothiocyanates
by Plant Myrosinase.
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Overview

• At least 120 chemically distinct glucosinolates
  have been identified in plants..
• Although the majority have been isolated from
  crucifers, 15 other families of plants are known
  to contain glucosinolates.
• The other families do include many edible
  species however, they are uncommon to the
  Western world and are thought to contribute
  little to our diets.
• Although only few attempts have been made to
  assess human glucosinolate consumption, some
  estimates are as high as 300 mg/d (660 µmol/d).

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Chemoprotective effects of isothiocyanates and
glucosinolates

• Since the early 1960s, both natural and synthetic
  isothiocyanates have attracted considerable and
  growing attention as important and effective
  protectors against chemical carcinogenesis in a
  number of animal models.
• Even though only a few glucosinolates have been
  examined (largely because adequate quantities of
  these compounds have been unavailable), some
  appear to be very effective in inhibiting
  carcinogenesis.

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History

• The history of these developments can be traced
  from the comprehensive review by Hecht and
  colleagues in which their work involved the NNK,
  which is probably the most prominent carcinogen
  derived from cigarettes..
• Several isothiocyanates inhibit the action of
  this carcinogen (NNK) through inhibition of its
  metabolism.

Hecht, SS. Chemoprevention of Cancer by
Isothiocyanates, Modifiers of Carcinogen
Metabolism. J. Nutr. 129 768S774S, 1999.
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Evidence

• Of the inverse association between crucifer
  consumption and cancer

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Bladder Cancer

• Michaud and colleagues analyzed 252 cases of
  bladder cancer that developed in 47,909 health
  professionals during a 10-y period.
• No significant associations were found bladder
  cancer and the consumption of
• Total fruits and vegetables
• Fruits only
• Vegetables only
• Or yellow or green leafy vegetables
• However, the multivariate risk reduction (RR)
  ratio
  for cruciferous vegetables was highly
  significant.

• Michaud DS, et al. Fruit and vegetable intake and
  incidence of bladder cancer in a male prospective
  cohort.
• J Natl Cancer Institute 91(7) 605-613, 1999.

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Fruit and vegetable intake and incidence of
bladder cancer in a male prospective cohort
Relative Risk P-value
Fruits and vegetables 0.75 0.25
Fruits 1.12 0.68
Vegetables 0.72 0.09
Yellow vegetables 1.01 0.50
Green leafy vegetables 0.99 0.81
Cruciferous vegetables 0.49 0.008
The only significant reduction in relative risk
was observed with cruciferous vegetables.
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• In the Health Professionals Follow-up Study,
  bladder cancer was only weakly associated with
  low intake of fruits and vegetables, but high
  intake (5 or more servings/week versus 1 or less
  servings/week) of cruciferous vegetables was
  associated with a statistically significant 51
  decrease in bladder cancer.

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Prostate cancer

• Cohen et al. examined the relationship between
  fruit and vegetable consumption and prostate
  cancer incidence in men lt65 y of age.
• High fruit consumption showed no effect on
  prostate cancer incidence.
• High overall vegetable consumption was associated
  with reduced risk.
• However, cruciferous vegetables were clearly
  protective when risk was adjusted for total
  vegetable consumption and other variables.

• Cohen JH et al. Fruit and vegetable intakes and
  prostate cancer.
• J Natl Cancer Institute 92(1) 61-68, 2000.

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• Also, prostate cancer risk was found to be
  reduced by cruciferous vegetable consumption in a
  population-based case-control study carried out
  in western Washington state.
• Three or more servings per week, compared to less
  than one serving of cruciferous vegetables per
  week resulted in a statistically significant 41
  decrease in prostate cancer risk.

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Breast cancer and non-Hodgkins lymphoma

• A case-controlled study in China found that
  intake of cruciferous vegetables, measured by
  urinary secretion of isothiocyanates, was
  inversely related to the risk of breast cancer.
• The quartile with the highest intake had only 50
  of the risk of the lowest intake group
• In the Nurses Health Study, a high intake of
  cruciferous vegetables (5 or more servings/week
  versus less than two servings/week) was
  associated with a 33 lower risk of
  non-Hodgkins lymphoma.

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Conclusions

• There is much evidence in regards to cruciferous
  vegetables and their role in the now widely
  recognized protective effects of vegetables
  against the risk of cancer.
• Much research has been done on the unusual
  phytochemicals known as glucosinolates found in
  cruciferous vegetables and their hydrolysis
  products, the isothiocyanates.

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Conclusions

• The isothiocyanates have already been established
  as playing a role in modulating the activities of
  enzymes involved in the metabolism of
  carcinogens, especially by the induction of phase
  2 detoxification enzymes.
• With time, a better understanding of the dynamic
  role that fruits and vegetables, in particular
  the cruciferous vegetables play in health and
  disease, will be uncovered.

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References

• Donaldson M. Nutrition Journal. 2004. Nutrition
  and cancer a review of the evidence for an
  anti-cancer diet. -
• Talalay P, Fahey J. Phytochemicals from
  cruciferous plants protect against cancer by
  modulating carcinogen metabolism. Journal of
  Nutrition. 2001.
• Hecht, SS. Chemoprevention of Cancer by
  Isothiocyanates, Modifiers of Carcinogen
  Metabolism. J. Nutr. 129 768S774S, 1999.
• Michaud DS, et al. Fruit and vegetable intake and
  incidence of bladder cancer in a male prospective
  cohort. J Natl Cancer Institute 91(7) 605-613,
  1999.
• Cohen JH et al. Fruit and vegetable intakes and
  prostate cancer. J Natl Cancer Institute 92(1)
  61-68, 2000.