The
Phytochemical Glossary
Here
is a list of terms used in phytochemical research.
-
A - Allium
compounds: Another
name for the organosulfides, or allyl sulfides, found in
allium vegetables, which include garlic, onions, leeks, chives
and shallots. Allium compounds such as diallyl sulfide and
allyl methyl trisulfide may boost enzyme cancer detox systems
and prevent bacteria from converting nitrates into substances
that help make carcinogens. Garlic lowers cholesterol in
people with elevated readings; diallyl sulfide is the suspected
operative. Garlic also reduces blood clotting and lowers
blood pressure. In addition to these and other possible health
benefits, organosulfides give the allium family its pungency.
But they may be lost in cooking.
Allyl
methyl trisulfide: See "Allium compounds."
Alpha
carotene: A
powerful antioxidant carotenoid that the body converts to vitamin A,
as needed. In population studies, alpha carotene is related to reduced
risk of lung cancer. It may slow the proliferation of cancer cells.
Carrots are a rich source.
Alpha
tocopherol: The most common form of vitamin E, found both
in the human body and in supplements. But gamma tocopherol is the primary
source of vitamin E in the American diet, chiefly because so many foods
such as margarine, salad dressings and packaged baked products are
made with gamma-rich soybean oil.
Anthocyanins: Probably
the most abundant flavonoid. See "Flavonoids."
Antioxidants: Antioxidants
are chemical magnets that disarm highly reactive and damaging forms
of oxygen, which are called collectively "free radicals." In chemicalspeak,
these molecules are reactive because they have an extra electron to
give away - and want to do it quick. Free radicals are the natural
byproducts of energy metabolism in the cell but also come from outside
sources. Although many phytochemicals are antioxidants, the most widely
recognized and researched are beta carotene and vitamins C and E.
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B -
Beta
carotene: A carotenoid that is stored in the liver, where
the body converts it to vitamin A, as needed; found in dark, leafy
greens and red, orange and yellow fruits and vegetables. A powerful
antioxidant, beta carotene may play a role in slowing the progression
of cancer. In population studies, it's related to decreased risk
of lung cancer and oral cancers. It also may enhance immunity, help
prevent
cataracts and slow plaque buildup in arteries. But it is not without
controversy: In a study of Finnish smokers, lung cancer increased
among those taking supplements. Similar problems occurred in a study
of former
smokers, smokers and workers exposed to asbestos. However, a 12-year
U.S. trial of more than 20,000 physicians, most of whom did not smoke,
showed no such increase nor any protective effect - for cancer or
heart disease. These findings don't negate beta carotene's promise,
but they
do complicate the picture for now.
Biochanin
A: See "Phytoesterogens."
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C -
Vitamin
C: The
most effective water-soluble antioxidant, especially abundant
in citrus fruits. Dr. Balz Frei, director of the Linus Pauling
Institute
at Oregon
State University, calls it the "first line of antioxidant defense in
human plasma." It works in concert with vitamin E to help
slow LDL oxidation, as well as protecting against some cancers.
It also protects
parts of the eye against oxidative damage from ultraviolet
light and may prevent cataracts.
Caffeic
and ferulic acids: Phenolic acids that in animal studies
prevent the formation of carcinogens in the stomach. Found in
virtually all fruits and vegetables.
Campesterol: See "Phytosterols."
Carcinogens: Cancer-causing
substances.
Carnosol: An
antioxidant phenolic compound in rosemary that may prevent cholesterol
oxidation and prevent cancer. Rosemary extracts are used in processed
foods as a preservative, but flavor limits their application.
Carotenoids: A
family of antioxidants that are also pigments in plants, giving
foods such as tomatoes, watermelon and sweet potatoes their bright
colors.
Although more than 600 have been identified, only a handful are
found in measurable quantities in the human body: alpha carotene,
beta
carotene, lycopene, lutein, zeaxanthin and cryptoxanthin. But
around a dozen
may be important. Carotenoids appear to play an anticancer role
and enhance immunity. Lycopene is increasingly gaining ground
as the
most powerful antioxidant in the carotenoid family, particularly
in relation
to prostate and breast cancer. Two carotenoids found in the eye,
lutein and zeaxanthin, are believed to protect against the leading
cause of
blindness in people over 65. Carotenoids also may play a role
in heart health: In LDL oxidation, antioxidants are consumed
in a sequence
that
begins with vitamin E; lycopene is next, followed by beta carotene.
Although carotenoids appear to be heat resistant, sunlight breaks
them down in the presence of oxygen, so don't cut up vegetables
and leave
them out on the counter for a long time before using them. Cooking
foods lightly makes their carotenoids more readily available.
Catechins: A
subclass of flavonoids found in tea. Up to 30% of the dry weight
of green tea leaves is catechins. Scientists believe catechins
to be one
of the important active substances that gives green tea extract
its cancer-preventive and possibly curative properties in animal
studies.
But population studies show no such clear-cut protective effect.
Chalcones: See "Flavonoids."
Cholesterol: A
important component of blood lipids (fats) manufactured by
the liver that's also the precursor of the steroid hormones,
such
as the sex
and "fight or flight" hormones. Too much of some kinds, specifically
low-density lipoprotein (LDL) and very-low-density lipoprotein
(VLDL), if oxidized, can collect inside artery walls as plaque,
restricting
blood flow, reducing vessel flexibility and leading to heart
disease. High-density lipoprotein (HDL) helps move LDL cholesterol
out of the
system. Vitamin E, lycopene and beta carotene protect LDL
from oxidation; their antioxidant activity is enhanced in
the presence
of vitamin C.
People concerned with cholesterol should watch their intake
of foods containing saturated fats, which stimulate the liver
to make more cholesterol.
Dietary cholesterol from animal-based foods has little effect
on blood cholesterol in healthy people.
Coumarins: A
class of widely occurring phenolic compounds, especially abundant
in citrus fruits, that may help the enzymes that fend off cancer.
Cryptoxanthin: A
carotenoid that's been associated with a decreased risk of cervical
cancer. Abundant in many orange fruits, especially mango, tangerines,
oranges and papaya.
Curcumin: A
phenolic compound that gives turmeric and mustard spices their
yellow color and exhibits anticancer, anti-inflammatory and antioxidant
properties.
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D -
Diadzein: See "Genistein."
Diallyl
sulfide: An allium compound that may have an anticancer
role and is suspected of being the active ingredient in
garlic that lowers cholesterol. See "Allium compounds."
Dithiolthiones: Organosulfur
compounds that are abundant in cruciferous vegetables and may
aid the enzymes that fend off carcinogens and other outside invaders.
They
also may inhibit the development of cancer.
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E -
Vitamin
E: The most potent fat-soluble antioxidant, as well
as one of the most widely recognized and researched. It
occurs in eight
chemical forms of varying potency; alpha tocopherol is
the most common. But
gamma tocopherol is the main type found in the American
diet because so many products are made with soybean oil.
Many kinds
of research
suggest that vitamin E works in concert with vitamin C,
interfering with LDL oxidation and protecting against heart
disease. But
another part of this protection, its anticlotting function,
may promote excessive
bleeding in some people. Vitamin E also may play a role
in immunity and in recovery from exercise-induced stress.
In one study it
delayed the onset of debilitating symptoms in Alzheimer's
disease. It also
shows anticancer promise. Getting enough E for such benefits
from diet alone without overdoing fat is difficult because
it's found
primarily
in oils, prompting many health experts to recommend taking
supplements. Recommendations range from 100 to 800 IUs
of vitamin E daily,
with most in the 200 IUs to 400 IUs range, and some specify
the natural
form, d-alpha tocopherol, or mixed tocopherols. One study
suggests that alpha and gamma tocopherol work in concert
more effectively
than individually against some particularly virulent free
radicals. But
the vitamin E research is far from definitive, and the
supplement recommendations, controversial.
Ellagic
acid: A phenolic acid with possible anticancer properties.
Found in nuts, particularly walnuts, and fruits such as
strawberries, cranberries and blackberries. But there is
question as to its
bioavailability (52).
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F -
Ferulic
acid: See "Caffeic acid."
Fiber: Population
studies suggest that a fiber-rich diet helps prevent
both cancer and heart disease. Scientists suspect that
one kind,
insoluble
fiber, prevents
colon cancer in particular, possibly by increasing
bulk and speeding waste through the colon, binding with carcinogens
and producing
anticancer substances along the way. Whole wheat and
wheat bran are rich sources.
The second type, soluble fiber, appears to lower cholesterol
and is abundant in oats, barley, legumes and vegetables
such as potatoes.
Most fruits, vegetables and grains contain a combination
of the two types. Americans currently consume about
13
grams of fiber
a day;
the
Daily Values
on food labels, based on a 2,000-calorie diet, suggest 25 grams.
Flavanones: See "Flavonoids."
Flavonoids: A
broad
subcategory
of
plant
phenolics
(or
phenolic
compounds)
made
up
of
more
than
4,000
compounds
that
are
found
in
fruits,
vegetables,
wine
and
tea,
especially
green
tea. "Plants have evolved to produce
flavonoids to protect against fungal parasites, herbivores, pathogens
and oxidative cell injury," writes Natalie Cook in a 1996 overview. "Conversely,
flavonoids produce stimuli to assist in pollination and guide insects
to their food source. For example, anthocyanins produce the pink, red,
mauve, violet and blue colors of flowers, fruits and vegetables." The
many
potential
effects
of
flavonoids
include
defending
cells
against
carcinogens,
curbing
the
oxidation
of
LDL
cholesterol
and
preventing
blood
clotting.
Major
flavonoid
classes
include
flavonols,
flavanones,
catechins,
anthocyanins,
isoflavones,
dihydroflavonols
and
chalcones.
Flavonols: See "Flavonoids" and "Quercetin."
Folic
acid: In the realm of cancer study, a deficiency
of this nutrient may lead to chromosome and/or DNA
damage that can open
the way for cancer. In heart research, low folate
causes high levels
of homocysteine in the blood, which increases the
risk for stroke and
heart attack. Found in dark leafy greens.
Free
radicals: Highly reactive molecular byproducts
of energy metabolism that can damage cells and DNA.
Free
radicals
also come from environmental sources such as cigarette
smoke, auto
and industrial
emissions and sunlight. A leading theory of aging
holds that free radicals
are largely responsible for the declines and diseases
associated with aging.
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G -
Genistein: An
isoflavone, like daidzein, uniquely abundant in soyfoods;
some of it is converted in the intestines to a compound
that acts
as a weak
estrogen
(phytoestrogen); the subject of hundreds of studies.
Scientists believe it may be a significant anticancer
force, particularly
with hormone-related
cancers such as breast cancer. It also may offer protection
against cardiovascular disease by reducing blood clotting
and/or cholesterol
levels. Further, it may play a role in bone health
and in relieving menopausal symptoms. See "Phytoestrogens."
Glutathione: A
water-soluble antioxidant found in onions and potatoes
that may detoxify cancer-causing substances. It also
supports the actions
of other
antioxidants, such as vitamins C and E and beta carotene.
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H -
HDL
cholesterol: See "Cholesterol."
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