Marcia Zimmerman

The scientific community has produced a growing body of evidence indicating how phytochemicals work to prevent disease. However, scientists are not sure if isolated, single phytochemicals offer the same benefits as those existing within chemically related groups, as occurs in whole food sources. Authorities caution that choosing foods containing naturally occurring phytochemicals is still the best health insurance. (1 )

All of these claims are due to “super nutrients” called phytochemicals that are helping to blur the line between food and medicine. They appeal to a better-educated public – one growing older, wealthier and more willing to self-medicate with foods and supplements. The question is whether these claims are valid. Do potato chips enhanced with unknown quantities of Ginkgo biloba really improve memory?

So-called “super foods” offer the promise of preventing cancer, decreasing heart attacks and improving brain function. Some of the more notable products with health claims now on store shelves include:

• Potato chips that enhance memory
• New age drinks that improve your love life
• A candy bar that reduces hot flashes
• A cookie that helps you bulk up and lean out
• Margarine that cuts cholesterol

Why the Frenzy Over Phytochemicals?

Phytochemicals are a group of nutritive components found in herbs, fruits, vegetables, grains, legumes, nuts, and spices. Animal foods contain a similar group of disease-preventing nutrients – the term zoochemical has been suggested for them. Phytochemicals and zoochemicals – unlike proteins, carbohydrates, fat, vitamins and minerals – are not considered essential for life and have therefore been assigned quasi-nutrient status. Several disease-preventive benefits have been proposed for phytochemicals and zoochemicals. Research shows individual nutrients can:

• facilitate cell-to-cell communication (13)
• modify cellular receptor uptake of hormones (12)
• convert to vitamin A (16)
• repair DNA damage from toxic exposure (23)
• detoxify carcinogens through the activation of the cytochrome P450 and Phase II enzyme systems. (24)
• serve as antioxidants, to help prevent various forms of cancer (2,3,4,5)
• cause apoptosis (cancer cell death)(20,21)
• enhance immune response (6,7)
• help prevent cardiovascular disease (8,9,10,11)
• help prevent osteoporosis (15)
• help prevent macular degeneration, and cataracts ( 17,18,19)
• may alter estrogen metabolism (14)
• help reduce the blood supply to tumors (angiogenesis) (22)

Phytochemicals and zoochemicals can be grouped into five families, based on their chemical structure and biological activity. The families include trpenes, organosulfur compounds, phenols, organic acids and polysaccharides, and lipids. Here is an overview of the families, what they do and what foods contain them:

 

Phytochemical Families

Family	What They Do	Where They’re Found
Terpenes
Carotenes, limonoids, saponins	Activate body’s protective enzymes, protect eyes, act as antioxidants, modify hormones, help block cholesterol absorption, protect cellular differentiation	Green, red and yellow vegetables and fruits; grains; legumes; nuts; seeds; herbs such as ginseng, chamomile, gotu kola
Organosulfur Compounds
Indol-3-carbinol, thiosulfonates, isothiocyanates	Boost cancer-fighting enzymes, block multagenesis, inhibit cholesterol synthesis, may lower blood pressure	Cruciferous vegetables; mustard family; onion & garlic family
Phenols
Polyphenols, anthocyanidins, caechins, isoflavones, tannins	Protect heart and vascular system, protect against colon cancer, modify hormone response, prevent dental caries	Berries, grapes, red wine, green leafy vegetables, soy foods, green tea, herbs
Organic acids, Polysacchaarides
Lactones, celluloses, arabinogalactans, pectins, fructans, glucans	Block nitrosamine effects, promote growth of beneficial intestinal bacteria, modulate immune system, may help prevent colon cancer	Fruit, mushrooms, yeast, herbs, spices
Lipids
Isoprenoids, oils, fatty acids, physterols	Reduct platelet aggregation, blood clotting, inflammation, nervous system disorders; balance hormones; modify autoimmune conditions	Dark-green leafy vegetables, nuts, soy oil, wheat germ, herbs, animal foods

 

Terpenes

Terpenes are a large class of compounds made up of single or multiple hydrocarbon units. Three groups include carotenes, limonoids and saponins. Single unit monoterpenes include d- limonene, an important anti-cancer agent, found in citrus fruits and alpha pinene, an anti-inflammatory and cancer preventive agent that occurs in fruits, vegetables and herbs. (25) Diterpenes include cancer preventive phytol (dill, chamomile, fenugreek, hops), and steviol (stevia leaf sweetener).  Important triterpenes (saponins) are asiaticosides and ginsenosides (ginseng, immune and cardio response modifiers; glycyrrhetic and glycyrrhizic acids (licorice), adrenal response modifers and hepatoprotectants (26). By far the most important terpenes are tetraterpenoids – the carotenoids.

Carotenoids are found in fruits and vegetables and have several biological activities that promote health. At least 600 different carotenoids exist; they are well-known phytochemicals because their bright colors distinguish foods that contain them.  Commonly consumed fruits and vegetables contain approximately 40 to 50 carotenoids, which are grouped into three categories, based on their color.

Yellow and orange fruits and vegetables-such as apricots, mangos, peaches, carrots, sweet potatoes and winter squash contain the greatest variety of carotenoids. Some of these are alpha, beta, delta, and  gamma carotenes; lutein, lycopene, neurosporene, phytofluene, phytoene and xanthophylls.  This group of fruits and vegetables provides vitaqmin A through bodily conversion of the alpha-, beta- and gamma-carotenes. They also protect DNA from damage, an occurrence that cdan result in unrestrained cellular growth. (15, 27,28 ) They also appear to protect against several cancers including  lung, colorectal, breast, uterine and prostate cancers.(29,30,31)

Red carotenoids, (pink grapefruit, pomegranates, berries, rhubarb, tomatoes and watermelon) contain an abundance of lycopene, zeta carotene, phytofluene and pytoene. All of these carotenoids are powerful oxygen free radical quenchers that help prevent prostate and skin cancer.(32,33)

Yellow/Green carotenoids appear to prevent age-related macular degeneration, cataracts, lower prostate, colon and uterine cancer risk (34,35,36,37,38). Yellow/Green fruits and vegetables (broccoli, collards, green beans, sweet corn, kale, romaine lettuce, chard, spinach, okra, green peas, summer squash, tangerines, turnip greens) contain lutein, zeaxanthin, alpha and beta carotene and beta cryptoxanthin.

Limonoids

Are an important class of monoterpenes naturally found in the peels of citrus fruits. In one study, a standardized extract of d-limonene, pinene and eucalyptol was effective in clearing congestive mucus from the lungs of patients with chronic obstructive pulmonary disease.(39) Limonoids also appear to be specific chemopreventive agents. (40) In animal studies, results suggest that the chemotherapeutic activity of limonoids can be attributed to induction of both Phase I and Phase II detoxification enzymes in the liver.(41) Perillyl alcohol is an important monoterperne from mandarin oranges that is an effective hypocholesterolemic and chemopreventive and chemotherapeutic agent.( 41) Perillyl alcohol and limonene are often paired in studies on cancer treatment.(42)

Phytosterols

Phytosterols occur in most plant species, with significant amounts found in the seeds of green and yellow vegetables.  Golden vegetables such as pumpkins, yams, and sweet potatoes provide phytosterols as do soy, wheat, corn, barley, oats, rice and most spices and herbs. An important benefit of phytosterols is reduction in absorption of dietary cholesterol, to which they are structurally similar,  through a mechanism of competitive uptake in the digestive system.(43)  They also bind cholesterol and facilitate its excretion from the body. (44)Cholesterol has long been implicated as a significant risk factor in cardiovascular disease.

Saponins

Are important antioxidants found in many of the same foods as phytosterols. Saponins appear to prevent mutations that can ultimately result in cancer. ( 45 ) Asian people for example, eat lots of rice, soy and vegetables rich in saponins.  It is thought these phytochemicals are a major reason for the low incidence of colon cancer in these populations. (46 )

Thiols

Phytonutrients of this family all contain various forms of sulfur which gives them a strong pungent character.  They are some of the most powerful protective agents. However, because cooking releases their odor and strong taste, they are often rejected by many Americans. The thiol group includes the onion and mustard families and cruciferous vegetables.  The sulfur compounds in these three groups are slightly different and consequently each has specific health benefits.

Glucosinolates

Found in cruciferous vegetables (Brassica, Crucifers, Mustard), glucosinolates are powerful activators of liver detoxification enzymes. (37) Bio‑transformation products of glucosinolates include isothiocyanates, dithiolthiones, and sulforaphane. The first three appear to block enzymes that promote tumor growth, particularly in the breast, liver, colon, lung, stomach and esophagus.(48)

Allylic Sulfides

Garlic and onions are the most potent members of this family which also includes leeks, shallots and chives. The allylic sulfides in these plants are released when the plants are cut or smashed. Once oxygen reaches the plants’ cells, various bio‑transformation products are formed – each with a different action.  Allicin, ajoene and S-allyl cysteine the products of raw garlic, are considered anti-atherosclerotic and anti cancer. Allicin and ajoene are also antibacterial, antiviral and antifungal. Allicin is also thought to moderate immune response. The best garlic antioxidants are allicin, the allyl sulfides and allyl mercaptan. (49) Garlic and onions, like their cruciferous relatives, can also activate liver detoxification enzyme systems. Specific allylic sulfides block the activity of toxins produced by bacteria and viruses.(50)

Indoles

Indol-3-carbinol, found in cabbage, is considered to be a potent anti-cancer agent and one of the most effective  dietary agents against colon cancer. (51) It interacts with vitamin C, commonly found in the vegetables that contain indoles. For many years, cabbage juice was consumed as a preventive and curative agent for bowel disorders.  It was thought to contain “cabbagen” or vitamin U. Later on, as the indole complex was discovered, the name was changed to “ascorbigen” and the vitamin designation was dropped.  Indole complexes bind chemical carcinogens and activate detoxification enzymes, mostly in the gastrointestinal tract. The bio‑transformation products of indoles are formed when they are acted on by stomach acid. (52) Indole-3-carbinol is one of a large class of phytoestrogens, natural products that are effective against hormone related cancers. (53)

Phenols

This is a large family of phytonutrients with over 2,000 family members. ( 54) The simplest phenols are compounds such as apiole (dill), thymol (thyme), carvacrol (oregano), geraniol and apiole (parsley), resveratrol (grapes), rosmarinol and rosmanol (rosemary). All  have along history or use as food preservatives.  In humans, they are powerful antioxidants, antifungal, antiseptic and anti-infective agents. ( 55 ) Resveratrol has been studied for its cardio- protective and anti-cancer effects. ( 56)

Polyphenols are multi-phenolic complexes that have an even wider range of biological activities.  They are natural components of vegetables, fruits, tea and herbs; apples, blueberries, cranberries, grapes, grape juice, strawberries, raspberries, red wine, green and black tea.  A large group of polyphenols including rutin, kaempferol, quercetin, hesperidin, narigenin have been collectively known as  “bioflavonoids.” The first three belong to a subset of flavonoids known as flavenols, are found in fruits and vegetables, and  are considered to have anti-histaminic, anti-inflammatory, antioxidant, anti-thrombotic and anti-tumor effects. ( 57 ) Hesperidin and narigenin (flavanones) are considered to have anti-inflammatory and anti-allergenic effects. (58 )

The polyphenols known as the flavan -3-ols that include catechins, proanthocyanidins, anthocyanidins and tannins have been extensively studied for their antioxidant, anticancer, antitumor and cardioprotective effects.  Hundreds of studies have been done on green tea catechins alone. ( 59 ) Red wine, grape juice, pine bark and grape seed extracts have been studied for their anti-thrombotic, antioxidant, cardiovascular and anticancer effects. (60 )

Isoflavones from soy products and red clover have weak estrogenic activity and accordingly are known as “phytoestrogens.”  Soy protein is a rich source of genistin, daidzin and glycetin that are converted by colonic bacteria into the bio-active isoflavones gensiten, daidzein and glycetein.(61 ).  The most studied properties of isoflavones are cardiovascular protection, prompting the Food and Drug Administration to allow a health claim for soy protein (minimum 6.25 g daily) for protection against cardiovascular disease – as part of a heart healthy diet.(62,63) Other benefits of soy protein include protection against some cancers (64) and relief from menstrual and menopausal symptoms. ( 65 ) A synthetic isoflavone called ipriflavone has also been shown to reverse osteoporosis (66)

Organic Acids, Polysaccharides, Esters and Lactones

Phytochemicals in this group are fairly simple carbon compounds commonly found in herbs, spices, teas, grains, a few vegetables and some fruit. These compounds act primarily as antioxidants, cancer preventives, hepatoprotectants, and inflammatory mediators. (67)  They include the acids; oxalic (spinach, rhubarb, tea, coffee), tartaric (apricots, apples), cinnamic (aloe, Kava), caffeic (burdock, hawthorn), ferulic (oats, rice), gallic (tea),  ellagic (guava), chlorogenic (echinacea), salicylic (peppermint) and tannic (nettles, tea, berries). Some are familiar because they are named for species from which they were first identified (ie, vanillic in vanilla bean).  Others such as gallic team up with phenols – in this case catechins – found in green tea, berries and grapes. Catechin-gallate complexes (esters) are “super-charged” antioxidants with enhanced anti-cancer and anti-tumor effects.( 68) The Kava lactones methysticin, dihydrokawain and kawain also belong to this family. Kava lactones account for the anti-anxiety, relaxant, anti-inflammatory and anti-pyretic effects of Kava Kava. (69)

Lipids

Isoprenoids

Isoprenoids are effective antioxidants with the unique property of anchoring themselves in membranes.  Vitamin E is the best known isoprenoid, offering protection for the many important molecules that make up cellular membranes, including the phospholipid layers and cellular receptors. Vitamin E works with other antioxidants such as vitamin C, co-enzyme Q 10, glutathione and alpha lipoic acid to completely disable free-radicals. Vitamin E is actually a family of isoprenoids that includes alpha, beta, delta and gamma tocopherols and tocotrienols, alpha through gamma.

Tocotrienols, along with vitamin E naturally occur in grains, rice and palm oil. along Tocotrienols appear to have tumor inhibiting properties, being effective against breast cancer cells, a property tocopherols do not seem to have.(70) Researchers have observed that the biologic functions of tocopherols and tocotrienols appear unrelated.(71) Tocotrienols have also been studied  for their cholesterol lowering effects.(72)

Ubiquinone (coenzyme Q) is an important part of the cellular antioxidant enzyme system.  Lipoic acid has been reported by scientists to be an efficient hydroxyl radical scavenger  its active site being a sulfur bond in the molecule.  Co Q is active on both lipids and water based fluids in the body. In addition to hydroxyl radicals, it scavenges peroxyl, ascorbyl and chromanoxyl radicals.  It’s lipid/water active properties enables protection for both vitamin E and vitamin C.  Lipoic acid also protects superoxide dismutase, SOD, catalase and glutathione – all part of the liver detoxification system.(73) The roles of both lipoic acid and ubiquinone as antioxidants have been discovered relatively recently. Both also have important roles in energy production from glucose.(74)

Omega -3 and Omega – 6 Fatty Acids

Alpha linolenic, an omega -3 fatty acid and linoleic, an omega – 6 fatty acid are widely found in dark green leafy vegetables, grains, legumes, seeds and nuts.  Both of these fatty acids are considered essential and are precursors of the two fatty acid phytochemical groups. Gamma linolenic acid, GLA (n-6) and eicosapentaenoic acid, EPA (n-3) are important moderators of prostaglandin pathways.(75)  They are considered anti-inflammatory, moderate immune response and cell membrane dynamics.  These activities result in protection against cardiovascular disease, cancer and many other forms of chronic disease. (76) Docosahexaenoic acid, DHA (n-3) is an integral component of brain membranes.  It has been effective in reducing disorders like schizophrenia, depression and attention deficits. (77) GLA comes from seed oils (primrose, borage, black current) and EPA and DHA are found in fish, especially salmon, herring, tuna, trout and white fish. Conjugated Linolenic Acid is found in cooked beef.  It has been shown to reduce some types of cancer in animal models.( 78)