Introduction to Phytochemicals


Phytochemicals can be defined, in the strictest sense, as chemicals produced by plants. However, the term is generally used to describe chemicals from plants that may affect health, but are not essential nutrients. There is ample evidence to support the health benefits of diets rich in fruits, vegetables, legumes, whole grains and nuts. Because plant-based foods are complex mixtures of bioactive compounds, information on the potential health effects of individual phytochemicals is linked to information on the health effects of foods that contain those phytochemicals.

Phytochemicals are plant or fruit derived chemical compounds. "Phytonutrients" refer to phytochemicals or compounds that come from edible plants.

Phytochemicals as therapeutics

There is abundant evidence from epidemiological studies that the phytochemicals in fruits and vegetables can significantly reduce the risk of cancer, probably due to polyphenol antioxidant and anti-inflammatory effects.

Phytochemicals have been used as drugs for millennia. For example, Hippocrates in 400 BC used to prescribe willow tree leaves to abate fever. Salicin, with potent anti-inflammatory and pain-relieving properties, was originally extracted from the White Willow Tree and later synthetically produced to become the staple over the counter drug called Aspirin.

The number one drug for cancer worldwide Taxol (paclitaxel), is a phytochemical initially extracted and purified from the Pacific Yew Tree.

Among edible plants with health promoting phytochemicals, Diindolylmethane, from Brassica vegetables (broccoli, cauliflower, cabbage, kale, Brussels sprouts) is currently used as a treatment for Recurring Respiratory Papillomatosis tumors (caused by the Human Papilloma Virus), it is in Phase III clinical trials for Cervical Dysplasia (a precancerous condition caused by the Human Papilloma Virus) and is in clinical trials sponsored by the National Cancer Institute of the United States for a variety of cancers (breast, prostate, lung, colon, and cervical). The compound has potent anti-viral, anti-bacterial and anti-cancer properties through a variety of pathways and it has also been shown to synergize with Taxol in its anti-cancer properties, making it potentially a very important anti-cancer phytonutrient as taxol resistance is a major problem for cancer patients worldwide.

Sometimes some of the compounds in plants with potent medicinal properties may not necessarily be chemicals, but may be elements, such as selenium found abundantly in Brassica vegetables with potent anti-viral and anti-cancer properties. In a human clinical trials, selenium supplementation has been shown to reduce the HIV viral load and is currently being recommended worldwide by physicians as an adjuvant nutritional supplement to AIDS treatments. It has also been shown to reduce mortality among prostate cancer patients.

There are currently many other phytochemicals with potent medicinal properties that are in clinical trials for a variety of diseases. Lycopene, for example, from tomatoes is in clinical trials for cardiovascular diseases and prostate cancer. Human clinical trials have demonstrated that lycopene helps to improve blood flow through the heart and clinical studies suggest anti-cancer activity against prostate cancer. Lutein and zeaxanthin from spinach have been shown through clinical trials to directly improve human visual performance and help prevent the onset of macular degeneration and cataracts.

In a landmark nutritional sciences study, scientists demonstrated that a diet rich in tomotoes and broccoli was more effective in inhibiting prostate cancer growth than a leading drug for prostate cancer. Clinical investigations are ongoing worldwide on thousands of phytochemicals with medicinal properties.

Food processing and phytochemicals

Phytochemicals in freshly harvested plant foods may be destroyed or removed by modern processing techniques, possibly including cooking[2][3]. For this reason, industrially processed foods likely contain fewer phytochemicals and may thus be less beneficial than unprocessed foods. Absence or deficiency of phytochemicals in processed foods is believed to have contributed to the increased prevalence of the above-cited preventable or treatable causes of death in contemporary society[citation needed]. Interestingly though, lycopene, a phytochemical present in tomatoes, is concentrated in processed foods such as spaghetti sauce and ketchup, making those foods better sources of lycopene than fresh tomatoes[citation needed].

The top 10 phytonutrient rich foods

* soy – protease inhibitors, beta sitosterol, saponins, phytic acid, isoflavones
* tomato – lycopene, beta carotene, vitamin C
* broccoli – vitamin C, 3,3'-Diindolylmethane, sulphoraphane, lignans, selenium
* garlic – thiosulphonates, limonene, quercitin
* flax seeds – lignans
* citrus fruits – monoterpenes, coumarin, cryptoxanthin, vitamin C, ferulic acid, oxalic acid
* blueberries – tannic acid, lignans, anthocyanins
* sweet potatoes – beta carotene
* chilli peppers – capsaicin
* legumes: beans, peas, lentils – omega fatty acids, saponins, catechins, quercitin, lutein, lignans

Other foods rich in phytonutrients or superfoods

Some animal derived foods are also considered superfoods. Beginning in 2005, there has been a rapidly growing recognition of several common and exotic fruits recognized for their nutrient richness and antioxidant qualities, with over 900 new product introductions worldwide[5]. More than a dozen industry publications on functional foods and beverages have referred to various exotic or antioxidant species as superfruits (see References[5]), some of which are shown in the list below.

* Apples – quercetin, catechins, tartaric acid
* Açaí berries – dietary fiber, anthocyanins, omega-3, omega-6, Beta-sitosterol. Açaí is the highest scoring plant food (spices excepted) for antioxidant ORAC value[6]

* Dried apricots
* Artichoke – silymarin, caffeic acid, ferulic acid
* Brassicates: kale, cabbage, brussels sprouts, cauliflower – lutein
* Carrots – beta-carotene
* Cocoa – flavonoids, epicatechin
* Cranberries – ellagic acid, anthocyanins
* Eggplant
* Gac – beta-carotene, lycopene
* Goji (Wolfberry) - ellagic acid, ?-carotene, ?-cryptoxanthin, zeaxanthin, lutein, lycopene
* Pink grapefruit – lycopene
* Red grapes and wine – quercitin, resveratrol, catechins, ellagic acid
* Green tea – quercitin, catechins, oxalic acid
* Mangos – cryptoxanthin
* Mangosteen - xanthones
* Nuts and seeds – resveratrol, phytic acid, phytosterols, protease inhibitors
* Porridge oats soluble fibre magnesium, zinc
* Okra -- beta carotene, lutein, zeaxanthin
* Olive oil – Monounsaturated fat
* Onions – quercitin, thiosulphonates
* Papaya – cryptoxanthin
* Bell peppers – Beta-carotene, vitamin C
* Pomegranate - Vitamin C, Tannins, especially Punicalagins
* Pumpkin – lignans, carotenes
* Quinoa Dietary fiber, protein without gluten with balanced essential amino acids
* Sesame - Lignans
* Shiitake mushrooms
* Spinach – oxalic acid, lutein, zeaxanthin
* Squash
* Watermelon – lycopene zeaxanthin, sulphoraphane, indole-3-carbinol
* Low fat yoghurt calcium
* Spirulina - beta-carotene

Phytonutrients Take Centre Stage

0n the cusp of the millennium, researchers are busily uncovering a host of beneficial compounds in plant foods. While these phytonutrients aren't essential by traditional definitions, they apparently reduce risks of diseases of aging.

For example, the isoflavones in soy products may reduce the risk of heart disease, osteoporosis, and several types of cancer. Certain flavonoids in blueberries may actually reverse nerve cell aging. And a wide array of compounds in fruits and vegetables may protect cell components against oxidative damage as well as vitamins C or E.

Indeed, cancer, heart disease, and Alzheimer's disease may plague the middle-aged and elderly because of our limited knowledge of phytonutrients. Research in this arena, now less than two decades old, may relegate some of today's ills to the history books—joining scurvy and pellagra.

Phytonutrients have provided the impetus for plant and nutrition scientists to work together because foods will continue to be the primary source of these compounds. While a few visionary plant scientists have improved the nutritional quality of foods, breeders have focused on increasing yields or warding off insects or diseases.

That is changing. Projects have sprouted up to screen germplasm for specific phytonutrients or to find ways to increase or preserve them in cultivated varieties. Following are just a few examples of this new wave:

Genetic engineering has produced tomatoes with up to three times more lycopene—the cancer-preventing red pigment—than normal and a shelf life several weeks longer. Autar K. Mattoo and colleagues at the ARS Vegetable Laboratory in Beltsville, Maryland, inserted a gene that retards plant aging, or senescence, along with a promoter that is triggered by ripening. The engineered tomatoes accumulate more lycopene and other antioxidants during the longer ripening stage. This novel approach should work in other fruits and vegetables.

Tissue culture at the ARS Western Regional Research Center in Albany, California, is producing tomatoes with 10 times more lycopene than store-bought tomatoes. Betty K. Ishida and colleagues grow tomatoes in test tubes kept at cooler temperatures, which triggers certain genes to produce the enzymes that increase lycopene production, she says. She is searching for the specific genes responsible and other ways to activate them.

Environmental and genetic factors also make a difference. Cantaloupes grown at the ARS Subtropical Agricultural Research Center in Weslaco, Texas, differed in beta carotene levels by 500 percent, depending on the soil, the cultivar, and fruit size, says Gene E. Lester. Now Lester and colleagues are embarking on a project to understand the postharvest storage factors, as well as the environmental and genetic factors that affect phytonutrient levels in a variety of fruits and vegetables.

Breeding will be central to putting produce with enhanced phytonutrients on the table. Broccoli is a good source of compounds that may inhibit cancer. But there's good potential for increasing the crop's potential anticancer punch. Mark W. Farnham in the ARS Vegetable Research Unit at Charleston, South Carolina, and Jed Fahey at Johns Hopkins University in Baltimore, Maryland, found that the supposed anticancer precursor—glucoraphanin—exhibits a thirtyfold difference in Farnham's inbred broccoli lines.

Storage can affect phytonutrient levels, says Irwin Goldman of the University of Wisconsin. Onions that have been in cold storage up to 90 days show more antiplatelet activity. This can reduce cardiovascular disease risk by interfering with the clumping of blood platelets—the first stage in clot formation.—By Judy McBride, Agricultural Research Service Information Staff.

This research is part of Human Nutrition, an ARS National Program (#107) described on the World Wide Web at

Beverly A. Clevidence heads the USDA-ARS Phytonutrients Laboratory, Bldg. 308, 10300 Baltimore Ave., Beltsville, MD 20705-2350; phone (301) 504-8367, fax (301) 504-9098.

Tracing Elements and Vitamins

A Chinese document dating back 5,000 years described goiter—an enlarged thyroid gland—and recommended that afflicted people eat seaweed and burnt sponge—both good sources of iodine. The element, however, was not recognized as dietarily essential until 1850.

Anemia, another deficiency disease, was treated around the 4th century B.C. by giving patients water used to quench heated iron swords. Iron itself was used to treat anemia as early as the 17th century. But the discovery of other essential elements didn't occur until the start of the 19th century. Sodium and potassium were soon followed by the other major minerals—calcium, sulfur, magnesium, and chlorine.

Except for iron and iodine, the essential trace elements—those needed in milligram or microgram quantity daily—remained unknown until the early 20th century. In the 1950s and 1970s, four elements considered toxic food contaminants—selenium, chromium, fluorine, and silicon—gained new respect when found to have a function in the body. And other trace elements are gaining essential status.

Vitamins, like minerals, had been hinted at for millennia. Diseases like beri beri—known in the Orient as early as 2600 B.C.—and scurvy—the sailors' curse—were long believed to be due to toxins from pathogens in the digestive tract. In 1747, British naval surgeon James Lind cured scurvy with lime juice—thus the term "limey" was coined to mean an English sailor.

Hippocrates advocated liver as a remedy for night blindness around the 4th century B.C., but the active component, vitamin A, was not chemically defined until 1913. The 1920s and 30s were ripe for vitamin discovery, accounting for 11 of the 15 vitamins. Now there's a new surge of discovery around health-enhancing compounds in plant foods known as phytonutrients.

See also

* Phytochemistry
* List of phytochemicals and foods they are prominent in
* Secondary metabolites


1. ^ Qualified Health Claims: Letter Regarding Tomatoes and Prostate Cancer (Lycopene Heath Claim Coalition) FDA Docket No. 2004Q-0201 November 2005[1]

2. ^ [2] Cooking and nutrient loss, World's Healthiest Foods

3. ^ [3] How processing affects berry nutrients, The Berry Doctor's Journal, August 2007

4. ^ Pratt S, Matthews K. SuperFoods Rx (2004) HarperCollins Books, New York ISBN 0060535679 [4]

5. ^ Starling, Shane. "Superfruits — superheroes of functionality", Functional Foods & Nutraceuticals, 2006-04. Retrieved on 2007-07-08. (English)

6. ^ Schauss AG, Wu X, Prior RL, Ou B, Huang D, Owens J, Agarwal A, Jensen GS, Hart AN, Shanbrom E. Antioxidant capacity and other bioactivities of the freeze-dried Amazonian palm berry, Euterpe oleraceae mart. (acai). J Agric Food Chem. 2006 Nov 1;54(22):8604-10.Abstract.


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* Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control Study Group. Journal of the American Medical Association.1994 Nov 9;272(18):1413-20. Seddon JM, Ajani UA, Sperduto RD, Hiller R, Blair N, Burton TC, Farber MD, Gragoudas ES, Haller J., Miller DT. Epidemiology Unit, Massachusetts Eye and Ear Infirmary, Boston 02114.

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