Phytonutrients are a class of nutrients that are thought to have health-protecting properties. The prefix phyto is from the Greek and means plant, and it is used because phytonutrients are obtained only from plants.
Unlike the macronutrients (proteins, carbohydrates, fats ) and micronutrients (vitamins, trace minerals ) that are needed for growth, metabolism, and other body functions, phytonutrients are not considered essential. This is because they can be lacking in the diet without harmful health consequences. However, throughout history, plants have been cultivated and used to prevent and treat various human diseases. More recently, understanding the chemical role played by these phytonutrients in plants has provided new clues as to how they may help humans. When eating plant-based foods, some of these phytonutrients identified as protectors in plants are transferred to our
Ways phytonutrients may protect human health
Serve as antioxidants
Enhance immune response
Enhance cell-to-cell communication
Alter estrogen metabolism
Convert to Vitamin A (beta-carotene is metabolized to vitamin A)
Cause cancer cells to die (apoptosis)
Repair DNA damage caused by smoking and other toxic exposures
Detoxify carcinogens through the activation of the cytocrome P450 and Phase II enzyme systems
More research is needed to firmly establish the mechanisms of action of the various phytochemicals
SOURCE:Agricultural Research Service, U.S. Department of Agriculture
(Illustration by GGS Information Services/Thomson Gale.)
bodies. The herbs and spices used for adding flavors and tastes to foods are now known to be associated with a long list of potential beneficial effects on human health. Phytochemicals derived from the plants to this day remain the basis of several medications used for the treatment of a wide range of diseases. Throughout the world, botanists and chemists actively search the plant kingdom for new phytochemicals. Over 40% of medicines now prescribed in the Unites States contain chemicals derived from plants. For example, ephe-drine, a phytochemical, is used in the commercial preparation of pharmaceutical drugs prescribed for the relief of asthma symptoms and other respiratory problems. Phytochemicals isolated from plants have also been a great help for discovering a large proportion of the drugs now available for the treatment of a wide range of human diseases such as pulmonary diseases, cardiovascular diseases, diabetes, obesity, and cancers.
There are three broad classes of phytonutrients: phytochemicals, medicinal plants and herbs and spices.
Thousands of phytochemicals have been isolated and characterized from plants, including fruits and vegetables. The most well-known include include ter-penes, carotenoids, flavonoids, limonoids, and phy-tosterols. In nature the bright green and red pigments present in cabbages and lettuce, tomatoes and strawberries have evolved to help absorb otherwise harmful ultraviolet radiation from the sun. They include the yellow, orange, and red carotenoids. Green and leafy vegetables are also rich in a carotenoid called beta-carotene. Flavonoids are other reddish pigments, found in red grape skins and citrus fruits. Other phy-topigments include lutein that makes corn yellow, and lycopene that makes tomatoes red. Aroma compounds in garlic and onions help protect plants from bacterial and viral infections. Others are enzyme blockers that forme to fight toxic pollutants. Plants have developed literally hundreds of thousands of naturally phyto-protective chemicals. It is therefore believed that if people consume them, they may gain some of these protective benefits. When extracted from plants, isolated phytochemicals are grouped into distinctive classes depending on the number and kind of atoms that they contain and according to the chemical structure of their main functional groups. The main classes of phytochemicals are:
- Alkaloids. This class contains molecules with cyclic carbon groups containing at least one nitrogen atom in the carbon ring. They are obtained chiefly from many vascular plants and some fungi and include steroids and some saponins extracted from beans, cereals, herbs.
- Aromatics. This class includes substances that contain a benzene ring that consists of six carbon atoms in a flat, hexagonal pattern and are found in aromatic plants such as garlic and onions.
- Flavonoids. Many are extracted from fruits, and vegetables. They include flavones (found in chamomile), flavonols (found in grapefruit and rutin-buck-wheat), flavanones (from citrus fruits, milk thistle) and the isoflavones (found in soy, peanuts, lentils).
- Indoles. Indoles, extracted from cabbage, are carbon compounds with two rings, a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring.
- Phytosterols. Sterols can be extracted from most plant species. Although green and yellow vegetables contain significant amounts, their seeds concentrate the sterols. Most of the research on phytosterols has been done on the seeds of pumpkins, yams, soy, rice and herbs.
- Terpenes. These are extracted from green vegetables, soy products and grains, and represent one of the largest classes of phytochemicals. The most intensely studied terpenes are carotenoids (from fruits, carrots). A subclass of terpenes are the limonoids found in citrus fruit peels.
It is well-known that plants produce phytochemicals to protect themselves and recent research increasingly shows that they may protect humans as well. Some examples of their health benefits include:
- Antioxidative properties. Most phytochemicals show antioxidant activity and are thus liable to protect lipids, blood and other body fluids from damage (oxidative stress) from reactive oxygen species while reducing the risk of developing certain types of cancer. Phytochemicals with antioxidant activity include allyl sulfides (onions, leeks, garlic), carotenoids, flavonoids, and polyphenols (tea, grapes).
- Hormonal properties. Isoflavones, also called phytoestrogens may function as human estrogens and help to reduce menopausal symptoms and osteoporosis.
- Enzyme stimulation. Indoles stimulate enzymes that lower the activity of estrogen and could reduce the risk for breast cancer. Other phytochemicals, which interfere with enzymes, are protease inhibitors (soy and beans) and terpenes.
- Interference with DNA replication. Saponins interfere with the replication of cell DNA, thereby preventing the multiplication of cancer cells. Capsaicin, found in hot peppers, is believed to protect DNA from carcinogens.
- Antibacterial properties. The phytochemical allicin from garlic has antibacterial properties. The intake of proanthocyanidins (from cranberries) will reduce the risk of urinary tract infections and will improve dental health.
- Cholesterol control. Phytosterols are believed to compete with dietary cholesterol for uptake in the intestines.
- Adhesion properties. Some phytochemicals bind to cell walls and it has been suggested that they prevent the adhesion of pathogens to human cell walls. Proanthocyanidins are responsible for the anti-adhesion properties of cranberry.
Medicinal plants have been used since the dawn of history to prevent and treat various diseases and disorders. They were first discovered by trial and error, for instance by noticing that pain went away when drinking tea made from the bark of a willow tree. It is only much later as science developed in the 20th century that chemists isolated salicylic acid from willow bark, the active ingredient in aspirin. Of the estimated 250,000 plant species, only 2% have been thoroughly investigated for phytochemicals with potential medicinal use. Some of the most well-known include:
- Aloe vera (Aloe vera). Heals wounds, emollient, laxative.
- Angelica (Angelica arcangelica). Antispasmodic, promotes menstrual flow.
Analgesic— A substance capable of producing analgesia, meaning one that relieves pain.
Antianemic— Preventing or curing anemia, a condition characterized by a lower than normal count of red blood cells.
Antiemetic— Agents that prevent nausea and vomiting. Antifungal—Substance that prevents the growth of fungi.
Antihyperlipidemic— Substance used in the treatment of very high serum triglyceride levels. Antimicrobial—Substance that prevents the growth of microorganisms including bacteria, viruses and fungi.
Antimutagenic— Substance that protects against genetic mutation.
Antinociceptive— Substance that reduces sensitivity to painful stimuli.
Antioxidative— A substance that inhibits oxidation.
Antipyretic— An agent that reduces or prevents fever.
Antitussive— Preventing or relieving cough.
Astringent— Tending to draw together or constrict tissues.
Atherosclerosis— Clogging, narrowing, and hardening of the body’s large arteries and medium-sized blood vessels.
Carminative— A substance that stops the formation of intestinal gas and helps expel gas that has already formed.
Demulcent— A substance that soothes irritated tissue, especially mucous membranes.
Diaphoretic— An agent that promotes sweating.
Emetic— A medicine that induces nausea and vomiting.
Emollient— An agent that softens and soothes the skin when applied locally.
Enzyme— A protein that accelerates the rate of chemical reactions.
Estrogen— A hormone produced by the ovaries and testes. It stimulates the development of secondary sexual characteristics and induces menstruation in women.
Expectorant— A substance that stimulates removal of mucus from the lungs.
Hematemesis— The medical term for bloody vomitus.
Intermittent claudication— Symptoms that occur when the leg muscles do not receive the oxygen rich blood required during exercise, thus causing cramping in the hips, thighs or calves.
Hypolipidemic— Promoting the reduction of lipid concentrations in the serum.
Hypotensive— Agent that lowers blood pressure.
Laxative— A medicine that helps relieve constipation.
Narcotic— An agent that causes insensibility or stupor; usually refers to opioids given to relieve pain.
Nervine— An agent that calms nervousness, tension or excitement.
Neurogenic bladder— An unstable bladder associated with a neurological condition, such as diabetes, stroke or spinal cord injury.
Osteoarthritis— A form of arthritis, occurring mainly in older persons, that is characterized by chronic degeneration of the cartilage of the joints.
Psoriasis— A chronic disease of the skin marked by red patches covered with white scales.
Sedative— A substance that reduces nervous tension.
Sialagogue— Promotes the flow of saliva.
Tonic— An agent that restores or increases body tone.
Trace minerals— Minerals needed by the body in small amounts. They include: selenium, iron, zinc, copper, manganese, molybdenum, chromium, arsenic, germanium, lithium, rubidium, tin.
- Arnica (Arnica montana). Anti-inflammatory, antimicrobial, muscular soreness, pain relief.
- Arrowroot (Maranta arundinacea). Anti-inflammatory, digestive, antiseptic.
- Belladonna (Atropa belladonna). Antispasmodic, narcotic, reduces sweating, sedative.
- Bergamot (Citrus bergamia). Disinfectant, muscle relaxant.
- Calendula, marigold (Calendula officinallis). Anti-inflammatory, astringent, heals wounds, antiseptic, detoxifying.
- Camphor (Cinnamomum camphora). Antiseptic, antispasmodic, analgesic, expectorant.
- Cardus, milk thistle (Carduus marianus). Digestive, liver tonic, stimulates secretion of bile, increases breast–milk production, antidepressant.
- Chamomile (Chamomilla recutita). Antiinflammatory, antiseptic, antispasmodic, relaxant, carminative.
- Clove (Eugenia caryophyllata). Antiseptic, mind and body stimulant, analgesic, antibacterial, carminative.
- Comfrey (Symphytum officinale). Antiinflammatory, wound healing, astringent.
- Dandelion (Taraxacum officinale). Diuretic, digestive, antibiotic.
- Eucalyptus (Eucalyptus globulus). Antiseptic, expectorant, stimulates local blood flow, antifungal.
- Gentian (Gentiana luted). Digestive stimulant, eases stomach pain.
- Ginkgo (Ginkgo biloba). Circulation stimulant and tonic, anti-asthmatic, antispasmodic, anti-inflammatory.
- Ginseng (Panax ginseng). Tonic, stimulant, physical and mental revitalizer.
- Hawthorn (Crataegus oxyacantha). Heart tonic, diuretic, astringent, dilates blood vessels, relaxant, antioxidant.
- Jasmine (Jasminum grandiflorum). Antispasmodic, expectorant.
- Juniper (Juniperus communis). Diuretic, antimicrobial, carminative, anti-rheumatic.
- Lavender (Lavandula officinalis). Carminative, relieves muscle spasms, antidepressant, antiseptic and antibacterial, stimulates blood flow.
- Malva, common mallow (Malva silvestris). Antiinflammatory, emollient, astringent, laxative.
- Melissa (Melissa officinalis). Relaxant, antispasmodic, increases sweating, carminative, antiviral, nerve tonic.
- Mistletoe (Viscum album).Tranquilizer, reduces pain, controls blood pressure.
- Motherwort (Leonurus cardiaca).Antispasmodic, hepatic, nervine, hypotensive, cardiac tonic.
- Nettle (Urtica dioica).Diuretic, tonic, astringent, prevents hemorrhaging, anti-allergenic, reduces prostate enlargement.
- Palmetto (Sabal serrulata).Tonic, diuretic, sedative.
- Passion flower (Passiflora incamata). Anti-inflammatory, antispasmodic, hypotensive, sedative.
- Peppermint (Mentha piperita). Carminative, relieves muscle spasms, increases sweating, stimulates secretion of bile, antiseptic.
- Rose (Rosa gallica). Antidepressant, sedative, antiinflammatory.
- Rue (Ruta graveolens). Antispasmodic, increases peripheral blood circulation, relieves eye tension.
- Sarsaparilla (Smilax sarsaparilla). Diuretic, antiinflammatory, anti-rheumatic.
- Scots pine (Pinus sylvestris). Antiseptic, diuretic and anti-rheumatic.
- St.-John’s wort (Hypericum perforatum). Antidepressant, antispasmodic, astringent, sedative, relieves pain, antiviral.
- Valerian (Valeriana officinalis). Sedative, relaxant, relieves muscle spasm, relieves anxiety, lowers blood pressure.
- Verbena (Verbena officinalis). Nervine, tonic, mild sedative, stimulates bile secretion.
- Witch hazel (Hamamamelis virginiana). Astringent, anti-inflammatory, stops external and internal bleeding.
- Wormwood (Artemisia absinthium). Stimulates secretion of bile, anti-inflammatory, eliminates worms, eases stomach pains, mild antidepressant.
- Yarrow (Achillea millefolium). Antispasmodic, astringent, bitter tonic, increases sweating, lowers blood pressure, reduces fever, mild diuretic and urinary antiseptic.
Herbs and spices
Spices have always been important in history. Spices belonged to the most valuable items of trade in the ancient and medieval world, providing the incentive for exploration and most great sea voyages of discovery. When Christopher Columbus discovered America, he described to his sponsors the many new spices available there. Herbs are leafy, green plant parts used for flavoring foods. They are usually used fresh. Unlike herbs, spices are almost always dried. Herbs and spices that are considered phytonutrients that are beneficial to health and have therapeutic properties include the following:
- Anise (Pimpinella anisum). Has carminative, sedative, antidepressant, antispasmodic, antifungal, and diuretic properties, used as a tonic.
- Bay leaves (Laurus nobilis). Has carminative, antifla-tulent, antimicrobial, antirheumatic, anticonvulsive and insect repellent properties.
- Black cumin (Nigella sativa). Has anti-inflammatory, analgesic, antioxidant, sedative, carminative, stimulant and anti-asthma properties.
- Black pepper (Piper nigrum). Used as a central nervous system stimulant, has analgesic and antipyretic properties.
- Caraway (Carum carvi). Used for flatulence, indigestion, and irritable bowel syndrome.
- Cardamom (Elettaria cardamomum). Has stimulant and carminative, digestive, anti-obesity, aphrodisiac properties.
- Cinnamon (Cinnamomum zeylanicum).Used against heartburn, heavy menstruation, peptic ulcer, poor appetite, yeast infections.
- •Cayenne Pepper (Capiscum frutescens). Topical use for diabetes, neurogenic bladder, osteoarthritis, pain and psoriasis.
- Celery (Apium graveolens L.). Used as antimicrobial, antifungal, and antihyperlipidemic agent.
- Coriander (Coriandrum sativum L). Used for treating bacterial infections, worm infections, indigestion, and inflammation.
- Dill (Anethum graveolens).Used against digestive problems
- Fennel (Foeniculum vulgare). Used against indigestion and irritable bowel syndrome.
- Garlic (Allium sativum).Used against atherosclerosis, high triglycerides, athlete’s foot, bronchitis, heart attack, high blood pressure, high cholesterol, intermittent claudication
- Ginger (Zingiber officinale). Used against motion sickness, nausea and vomiting following surgery, morning sickness, and chemotherapy.
- Lemon Grass (Cymbopogon citratus). Has antimicrobial, antifungal, antibacterial, and mosquito repellent properties.
- Marjoram (Origanum majorana). Has carminative, antispasmodic, diaphoretic, and diuretic properties.
- Mustard (Brassica alba). Used as an emetic and a muscle relaxant.
- Nutmeg (Myristica fragrans). Has carminative, hallucinogenic, stimulant, expectorant, and sialagogue properties.
- Onion (Allium cepa L). Used against pain, diarrhea, hematemesis, diabetes, asthma, cough and tumors.
- Oregano (Origanum vulgare). Has antifungal and antimicrobial properties and protects against colds.
- Paprika (Capiscum annuum). Has anti-inflammatory and antinociceptive properties, and is used as a circulatory stimulant
- Parsley (Petroselinum crispum). Has antihyperlipidemic, anticoagulant, antimicrobial, antioxidative, antianemic, and laxative properties, used as a tonic.
- Red beet root (Beta vulgaris). Has antioxidant and liver-protecting properties
- •Saffron (CrocussativusL).Has antispasmodic, diaphoretic, carminative, heart-protective, hypolipidemic, antitussive, antioxidant, sedative, and memory-enhancing properties.
- •Sage (Salvia officinalis). Used against night sweats and to relieve oral cavity and throat inflammations.
- Savory (Satureja hortensis L). Has antibacterial, antifungal, antioxidative, antispasmodic, antidiar-rheal, sedative, and anti-inflammatory properties.
- Sesame (Sesamum indicum). Used as a tonic and a laxative, emollient, demulcent, has antidiabetic and antioxidant properties.
- Spearmint (Mentha spicata).Has antibacterial, antiinflammatory, carminative, analgesic and antimuta-genic properties.
- Sweet basil (Ocimum basilicum L). Has antioxidant, heart-protective, anti-fertility, anti-diabetic, liver-protective, anti-inflammatory, antifungal, antimicrobial, antiemetic, antispasmodic, and analgesic properties.
- Thyme (Thymus vulgaris). Has carminative, and antitussive properties.
There are no recorded harmful effects associated with medicinal plants, nor with herbs, and spices, except for unpalatable food when used in exaggerated quantities. Phytochemicals in isolated forms, however, can have adverse effects on some people and may not provide all of the health benefits of the whole plant foods they were extracted from. Phytonutrients are relatively new in nutritional public awareness. While there is ample evidence to support the health benefits of diets rich in plant foods such as fruits, vegetables, whole grains and nuts, hard evidence concerning the benefits of specific phytonutrients is limited. This is because plant-based foods are complex mixtures of numerous bioactive compounds, and information on potential health effects is linked to information on the health effects of foods that contain a group of phytochemicals rather than on the effect of a specific phy-tochemical. A wealth of information exist about vitamins and minerals, but researchers are still trying to determine scientifically the types of phytochemicals that are present in foods, how they interact with each other and the body and what their health benefits are. There is also a trend to package and promote phyto-nutrient supplements as the new magic cure for all diseases and disorders, which makes it difficult to assess the claims that are made concerning their benefits. Taken in the form of supplements, caution should accordingly be exercised to avoid excessive intake. For example, carotenoids are not toxic to the human body. An excessive intake of carrots and other vegetables containing carotene can lead to a yellowing of the skin, in itself harmless. However, beta-carotene in the form of a phytonutrient supplement be dangerous for smokers and people exposed to secondhand smoke or asbestos. The American Cancer Society has requested that warning labels for these people be placed on phytonutrient supplements containing any isolated form of vitamin A or beta-carotene.
Though beneficial for certain conditions, phytonutrient supplements can not always capture the many different interactions of the phytonutrients found in food. For example, flavonoids and carotenoids are believed to have more health-promoting properties when they are taken together rather than separately in a supplement. The hundreds of phytonutrients present in plant foods help each other biochemically—and presumably also in the body. The food science and pharmaceutical developments of the past decades have consistently demonstrated the need to consume a broad range of whole foods on a regular basis. Eating a whole tomato is better than taking a supplement that contains a phytochemical isolated from a tomato. Eating a carrot does not only provide the beta carotene that could be obtained in a pill, but also the health benefits of hundreds or thousands of other phytonutrients that have not yet been identified or characterized. Some interactions are possible between phytonutrients. Citrus bioflavonoid preparations, such as grapefruit juice, may interact with drugs containing naringin. Naringin increases the oral bioavailability of calcium channel blocker medications such as: nifedipine, verapramil and felodipine. Naringin may enhance the effect of these drugs and result in a serious drop in blood pressure. Naringin also inhibits the breakdown of various drugs such as caffeine, coumarin, and estrogens. It is recommended to avoid flavonoid preparations containing naringin when taking any of these drugs. Studying the health benefits of individual phytonutrients is just one aspect of understanding how fruits and vegetables contribute to health, buy much research remains to be done on how the phytonutrients interact with each other and how they may protect against disease.
In case of adverse or allergic reaction, the use of phytonutrient supplements should be discontinued.
One risk associated with phytonutrients is if they are taken as supplements because they are then in a concentrated and more potent form. Hence, some may cause allergic reactions in hypersensitive people. They should also be kept out of reach of children. As with any nutritional supplement, a healthcare professional should be consulted if taken by pregnant or lactating women or by people with health conditions. For example, cauliflower contains goitrogens that can interfere with the functioning of the thyroid gland. Individuals with already existing medical problems may have to avoid specific phytonutrients.
There is a danger that phytonutrient classifications over-simplify the process of building a healthy diet. Most foods are packed with protective phytonutrients. They are present in all plant foods, and eating a wide variety of fruits and vegetables should be preferred to taking specific supplements, unless recommended by a health practitioner. Information on the disease-fighting functions of phytonutrients is becoming widely available and should be used to understanding their many properties. It is not possible to cover all of the cautions for people considering the purchase of phytonutrient supplements. However, one simple sentence covers whole foods and whole food supplements: they can be a safe and important method by which people improve their health and well-being because they are made from the whole fruit or vegetable and do not just contain isolated components.
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Monique Laberge, Ph.D.
Polynesian diet seePacific Islander diet