is a list of terms used in phytochemical research.
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.
methyl trisulfide: See "Allium compounds."
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.
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.
the most abundant flavonoid. See "Flavonoids."
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.
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.
A: See "Phytoesterogens."
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.
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."
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.
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.
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."
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.
class of widely occurring phenolic compounds, especially abundant in
citrus fruits, that may help the enzymes that fend off cancer.
carotenoid that's been associated with a decreased risk of cervical
cancer. Abundant in many orange fruits, especially mango, tangerines,
oranges and papaya.
phenolic compound that gives turmeric and mustard spices their yellow
color and exhibits anticancer, anti-inflammatory and antioxidant properties.
Diadzein: See "Genistein."
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."
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.
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,
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
acid: See "Caffeic acid."
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
Flavanones: See "Flavonoids."
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."
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.
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
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."
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.
cholesterol: See "Cholesterol."
Indole-3-carbinol: See "Indoles."
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.
hexaphosphate: See "Phytic acid."
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."
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.
flavonoid, like quercetin, found broadly in fruits and vegetables.
LDL cholesterol: See "Cholesterol" and "Oxidation."
(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.
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
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.
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.
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.
abundant in olive oil and canola oil. Monounsaturated fats slightly
lower total cholesterol; this action may be due to their phytosterols.
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.
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.
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.
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.
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.
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).
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.
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.
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
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.
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.
naturally occuring phenolic fungicide in grapes (and wine) that may
that protect the heart. Peanuts also contain resveratrol.
name for vitamin A. See "Carotenoids."
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.
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.
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.
(beta-sitosterol): See "Phytosterols."
Stigmasterol: See "Phytosterols."
Sulphorophane: See "Isothiocyanates."
and triterpenes comprise the terpenes under investigation. Most of
the attention is focused on two monoterpenes: limonene and perillyl
phenolic compound in vanilla beans and cloves.
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.