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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I -
Indole-3-carbinol: See "Indoles."
Indoles: Found
in cruciferous vegetables, indoles may prevent
carcinogens from reaching their intended goal inside
of cells.
They're formed
from glucosinolates,
which are particularly abundant in brussels sprouts,
rutabaga and mustard greens. One, indole-3-carbinol,
may help protect
against
estrogen-related
cancers, such as breast cancer.
Inositol
hexaphosphate: See "Phytic
acid."
Isoflavones: Genistein
and daidzein are the most prominent; found almost
exclusively in soybeans and soyfoods; some are
converted in the
intestine to compounds
with
estrogen-mimicking functions; may help prevent
hormone-related cancers, such as breast cancer.
Sometimes scientists
will refer to foods as "containing
isoflavones" as a kind of shorthand. See "Genistein."
Isothiocyanates: Among
the most effective cancer-prevention agents known.
These organosulfur compounds boost the cancer-fighting
power
of certain enzymes.
One, sulphorophane, appears to be especially potent.
They are partially
responsible for the pungency of some cruciferous
vegetables.
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K -
Kaempferol: A
flavonoid, like quercetin, found broadly in fruits
and vegetables.
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L -
LDL cholesterol: See "Cholesterol" and "Oxidation."
Lignans
(also called phenolic lignans): Plant
phenolics converted in the intestines to
a type of phytoestrogen ("plant" estrogen)
with antioxidant properties. As a weak estrogen,
lignans may affect hormone-related cancers
by tying up the estrogen
receptors on cells.
Lignans are abundant in flax seed and flour,
whole grain products and some berries. Vegetables
and other
grains are
also sources.
Limonene: This
monoterpene, which shows so much promise for
cancer treatment, is the same substance that
gives lemon
scent to furniture
polish and
grease-cutting
power to detergent. (One scientist once described
how it dissolved a researcher's plastic pipette.)
It is
found in citrus oils,
as well as garlic and the oils of other plants;
it is used
in Japan to dissolve
gallstones. Limonene and its chemical cousin,
perillyl alcohol, show powerful anticancer
effects in animals.
In rats, limonene
caused
the complete regression of mammary tumors.
Human studies are underway with
cancer patients.
Lutein: A
powerful antioxidant and one of two carotenoids
found in the eye. These yellow pigments are
believed to filter
out
harmful
blue light
and protect
against age-related macular degeneration, the
leading cause of blindness in people over 65.
Studies show
that eating
lots of
spinach and collard
greens - rich in lutein and its carotenoid
partner, zeaxanthin - may substantially lower
the risk
of this irreversible
disease. More
resistant
to cooking than other carotenoids, it's also
associated with decreased lung cancer risk.
Lycopene: Emerging
as the most powerful antioxidant of the carotenoid
family. The pigment gives tomatoes their red
color and also makes
grapefruit
and watermelon
pink. The most concentrated carotenoid in the
prostate, lycopene is linked to reduced prostate
cancer risk
in population studies.
In one
study, it inhibited cancer cell proliferation
more effectively than alpha carotene or beta
carotene.
It is also stirring
interest as
a possible breast cancer preventative.
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M -
Monoterpenes: A
broad category of compounds that may prevent,
slow and/or reverse the progression of some
cancers as well as affect
blood clotting
and cholesterol.
The two most notable are limonene and perillyl
alcohol. Found in the essential oils of citrus
fruits, cherries,
spearmint and
dill.
Monounsaturated
fats: Especially
abundant in olive oil and canola oil. Monounsaturated
fats slightly lower total cholesterol; this
action may be due
to their phytosterols.
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N -
Nitrates,
nitrites: Nitrosamines are known to
cause cancer. Nitrites in smoked and fermented
foods and nitrates,
found naturally
in some foods and changed to nitrites by
bacteria in the mouth,
combine with
amines in the stomach as protein breaks
down
to form nitrosamines. Vitamins C and E
and phenolic compounds,
such as quercetin,
block this reaction in the stomach and
may thus prevent cancer. Nitrates
and nitrites
are also found in some cured meats.
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O -
Organosulfides: The
mostly smelly compounds in the allium
(onion-garlic) and cruciferous
(broccoli-kale) families. Dithiolthiones,
including sulforophane, and indoles are
the dominant ones in the cruciferous
vegetables; they work primarily against
cancer. Allium compounds such as diallyl
sulfide are operative in the allium vegetables,
especially
garlic;
they have
a variety of
anticancer
and heart health functions.
Oxidation: Occurs
when something is chemically united with
certain types of oxygen with the help
of an oxidizing
agent. Combustion
- fire - is the
result of
oxidation. It also occurs when metals
rust or cut apples or potatoes turn brown.
(Squeezing
lemon
juice on apples
to prevent discoloration
is an example of an antioxidant in action.)
In
the body, highly reactive free radical
forms of oxygen
grab onto
other compounds
in cells,
causing structural damage to cell protein
or fats or to the DNA within the
nucleus. Polyunsaturated fat molecules
in cell membranes and LDL cholesterol
are particularly
susceptible to
free radical
damage.
Oxidized LDL cholesterol
changes readily into substances that
contribute to lesions in blood vessel
walls, building
up as plaque
that gradually
shrinks
the circumference
of the vessels and makes them less flexible.
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P -
Perillyl
Alcohol: The limonene cousin that
has been shown in animal studies to
shrink tumors in
animals, including
stubborn
pancreatic
tumors. Found in citrus oils, this
monterpene is being tested on humans.
The intervention
trials are using
amounts far greater
than
what is
ordinarily consumed from fruits and
vegetables.
Phenolic
compounds (or plant phenols): A
broad category of antioxidant compounds
that
includes flavonoids,
phenolic
acids (which
includes ellagic acid, tannic acid
and vanillin) and hydroxycinnamic acid
derivatives (caffeic, chlorogenic and
ferulic acids, curcumin, coumarins).
Lignans
are another class of phenolic compounds.
Found in almost all fruits, vegetables
and grains,
phenolic compounds
affect the
quality, appeal
and stability of foods with antioxidant
action, flavor and color. They give
wine
its characteristic
hues,
flavors and astringency.
Besides
scavenging for free radicals, some
phenolic compounds appear to interrupt
cancer
development in other
ways. Some also
hinder LDL oxidation.
It's not yet known how well plant phenols
are absorbed from foods.
Phytic
acid (inositol hexaphosphate): A
heat- and acid-stable phytate in cereal
grains,
nuts and
seeds, especially
abundant in sesame
seeds and soybeans. Although a high-fiber
diet is thought to protect against
some cancers, the argument has been
advanced that phytic acid, not fiber,
may provide
the protection.
It appears
to slow the
formation
of cancer in lab and animal studies.
It also may help control blood sugar,
cholesterol
and triglycerides.
Phytoestrogens: So-called "plant" estrogens
that are produced in the intestines from certain flavonoids, isoflavones
(most notably genistein, biochanin A and daidzein) and lignans. Often
scientists simply say foods "contain" isoflavones
as a kind of shorthand. Phytoestrogens
are 250 to 1,000 times weaker
than human estrogen but
still impact the body. They are
suspected of blocking estrogens
by tying up
estrogen receptors on cells,
thus affecting hormone-related
cancers, including breast and prostate
cancer. They also may decrease
hot flashes and other symptoms
of menopause, although most of
the evidence
is anecdotal
so far. One scientist
likens
phytoestrogens to a key that
can fit a lock but not open it,
effectively blocking the real key.
Some phytoestrogens
are similar to
tamoxifen, a
drug used to treat
some breast cancers. Soyfoods are
rich sources. In one study, tofu
was found
to contain the most isoflavones
of the foods
tested, though
amount varied by brand (53).
Phytosterols: Plant
sterols that in modest amounts can
lower cholesterol and that show anticancer
activity in lab and
animal studies. Nuts (almonds,
cashews,
peanuts), seeds (sesame, sunflower),
whole wheat, corn, soybeans and many
vegetable
oils are good
sources.
Some scientists speculate
that
phytosterols are responsible for the
cholesterol-lowering properties of
mono-
and polyunsaturated
oils. Some key sterols that lower
cholesterol are beta-sitosterol, stigmasterol
and campesterol.
Polyunsaturated
fats: Like monounsaturated fats,
polyunsaturated fats lower cholesterol.
Two groups of polyunsaturated
fats,
omega-3s and
omega-6s, are essential fatty acids,
which the body requires but cannot
manufacture. Omega-6s are in seeds
and in vegetable
and seed oils. Omega-3s are in green
leafy
vegetables,
canola oil
and soybeans.
In slightly different
form, omega-3s are found in fish and
especially concentrated in cold-water
fish such as
salmon, trout, sardines
and mackerel. (The source of
these plant substances in fish are
plankton and
algae.) Because omega-3s and omega-6s
compete for the same
enzymes in the body,
excessive
intake
of omega-6 can lead to a relative omega-3
deficiency.
Pro-oxidant: Any
chemical compound that enhances oxidation.
Under some conditions, some phytochemicals
have been
shown to
act as pro-oxidants,
one reason scientists
wave people off supplements. Americans
often assume - wrongly - that if a
little of something
is good,
a lot
must be
better. If you're
talking spinach, you probably can't
(or won't) eat too much; if you're
talking
milligrams of sulphorophane in a capsule,
you might do harm. With the exception
of vitamin
E, too little
is
known about most
phytochemicals
to mega-dose.
Protease
inhibitors: Proteins that are plentiful
in plants. Lab and animal studies show
that they
may aid DNA repair,
which can slow
cancer cell division and help return
a cell to its normal state. They also
may prevent tumors from releasing proteases
that destroy neighboring cells. Found
especially
in
soyfoods, also
seeds and legumes.
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Q -
Quercetin: The
most studied flavonoid because
it is among the most abundant; a more potent
antioxidant
than
vitamin E, according to
some research. Onions
are the richest source; it's also
found in wine and
tea. (Many sources say "onions, tea, wine and apples" because
these were the main dietary sources
in a major Netherlands study.)
Among other functions, it may
block carcinogens as well as slow
the growth and spread of cancer
cells. It also may prevent the
conversion
of nitrites
in the stomach to compounds
that become building blocks for
carcinogens. Quercetin appears
to survive the heat of cooking,
and about
5% to 10% of the
quercetin from onions
is absorbed by the body.
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R -
Resveratrol: A
naturally occuring phenolic fungicide
in grapes (and wine) that may that
protect the heart.
Peanuts also
contain resveratrol.
Retinol: Another
name for vitamin A. See "Carotenoids."
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S -
Saponins: Naturally
occurring compounds found in most
vegetables and herbs, but especially
abundant
in soybeans and
other beans
and legumes. Lab and animal
research with saponins suggests
they may prevent cancer cells from multiplying.
They may also help control blood
sugar, cholesterol and triglycerides.
Selenium: A
trace mineral that may alter the
course of cancer by helping certain
enzymes
protect cells against
damage.
The amount
found in produce
is directly related to the amount
in the soil where it is grown,
and selenium
is readily taken up by the body.
Its antioxidant
function may prevent premature
aging. Garlic contains selenium,
and one scientist
has
used enriched soil to increase
the
amount in garlic bulbs.
Silymarin: A
flavonoid present in artichokes
that has been used in Europe to
treat
alcohol-related liver
diseases.
This
strong antioxidant
protects
against liver toxicity in animals
and plays
a cancer-protective role.
Sitosterol
(beta-sitosterol): See "Phytosterols."
Stigmasterol: See "Phytosterols."
Sulphorophane: See "Isothiocyanates."
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-
Terpenes: Monoterpenes
and triterpenes comprise the terpenes
under investigation. Most of the
attention is
focused on two monoterpenes:
limonene and
perillyl
alcohol.
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V-
Vanillin: A
phenolic compound in vanilla
beans and cloves.
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Z -
Zeaxanthin: A
strong antioxidant and one
of two yellow carotenoids
found in the
eye that are
believed to filter
out harmful blue
light and
protect
against
age-related macular degeneration,
the leading cause of blindness
in people
over 65. Studies
show that
eating lots of spinach and
collard greens - rich in
zeaxanthin and its carotenoid partner,
lutein -
may
substantially lower the risk
for this irreversible condition.
Also in the eye, the antioxidants
may help scavenge free radicals
caused by exposure to sunlight.
Zeazanthin
is also associated with decreased
lung
cancer
risk.
Corn and eggs
are also good sources.
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