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.
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.
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.
•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
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.
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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