Mom's favorite pearl of wisdom was always - "Make sure you eat all your vegetables!" and mom was right. Throughout the ages, people have found that consuming certain plants, or parts of plants, relives aches and pains. Some people believe that vitamins, minerals, and fiber are the only healthy thing we get from plants, but this is not true. Plants are an essential part of our diet because they contain chemicals, known as phytochemicals that ensure a healthy diet, prevent heart attacks and chronic diseases like cancer, and improve brain function. Phytochemicals give plants their color, flavor, smell, and texture, and they are contained within a variety of fruits, vegetables, grains, herbs, legumes, nuts and spices (American Dietetic Association 1999; Homsey 1999).
Although phytochemicals are not yet classified as nutrients, substances necessary for sustaining life, they have been identified as containing properties for aiding in disease prevention (Homsey 1999). Phytochemicals are associated with the prevention and/or treatment of at least four of the leading causes of death in the United States - cancer, diabetes, cardiovascular disease, and hypertension (American Dietetic Association 1999; Homsey 1999; Messina 1997). They are involved in many processes including ones that help prevent cell damage, prevent cancer cell replication, and decrease cholesterol levels (American Dietetic Association 1999; Homsey 1999; Zimmerman 2000). With health-care costs being a major issue today, it would be cost effective to continue the research needed to help promote the awareness and consumption of phytochemicals as a prevention strategy for the public (American Dietetic Association 1999).
Individual phytochemicals are being evaluated for their safety and effectiveness in regard to disease prevention. Although most studies support positive outcomes, there are a few studies involving animals that show possible detrimental effects. These studies involve animals and specific extracted phytochemicals in high dosages (American Dietetic Association 1999). Researchers ask, "Should one increase the intake of a particular plant food containing phytochemicals, and how much should they increase it?" Clearly, like any other newly discovered chemical, there is a need for further investigation for potential health benefits and possible health risks (American Dietetic Association 1999). Optimal levels of phytochemicals have yet to be determined. In addition, requirements during disease states may differ from requirements for prevention of heart disease and cancer. Individual recommendations in terms of requirements for different genders, age groups, body types, and so forth also need further study (American Dietetic Association 1999).
According to Zimmerman (2000), phytochemicals can be grouped into five families based on their chemical structure and biological activity. The families include: terpenes, organosulfur compounds, phenols, organic acids and polysaccharides, and lipids. Terpenes are a large class of compounds made up of single or multiple hydrocarbon units. Three groups include the carotenes, limonoids and saponins. By far the most important terpenes are 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 groups of 40 to 50 carotenoids, which are grouped into three categories based on their color. Yellow-orange carotenoids appear to protect against several cancers including breast, colorectal, lung, prostate and uterine. Yellow and green fruits and vegetables appear to prevent age-related macular degeneration and cataracts as well as to lower uterine cancer risk. Red carotenoids are free radical quenchers that may help prevent prostate cancer. Limonoids form an important class of monoterpenes naturally found in the peels of citrus fruits. In studies they reduce the need for antibiotics, the frequency and intensity of acute bronchitis flareups and bouts of coughing. Saponins are found primarily in legumes, with the greatest concentration occurring in soybeans. Recent experimental investigations suggest that saponins have cholesterol-lowering, anticancer and immuno-stimulatory properties. Anticancer properties of saponins appear to be the result of antioxidant effects, immune modulation and regulation of cell proliferation.
Phytonutrients of the organosulfur compound family contain various forms of sulfur, which give them their characteristic pungent aroma. They are often rejected by Americans because cooking intensifies their odor and strong taste. Oddly enough, cooking can also boost their protective powers. The organosulfur group includes the cruciferous vegetables, such as bok choy, broccoli, brussel sprouts, cabbage, kale and turnips, and the onion and mustard families (Zimmerman 2000). Glucosinolates are found in cruciferous vegetables and the mustard family. Broccoli glucosinolates are thought to activate protective liver enzymes that detoxify potential carcinogens and facilitate estrogen conversion into estrogen conjugates that are eliminated from the body. Indoles bind to chemical carcinogens and activate detoxification enzymes. Thiosulfonates are most notably found in onions and garlic as well as in chives, leeks and shallots, which are considered antiatherosclerotic and anticancer agents. Isothiocyanates are found in several cruciferae, including mustard greens and seeds, daikon, horseradish and wasabi. Isothiocyanates inhibit esophageal, lung and several other cancers (Zimmerman 2000).
Phenols are a large family of phytonutrients has more than 2,000 family members. The simplest compounds are single phenolic units found in abundance in culinary herbs. These include dill and parsley, oregano, and rosemary. In humans, they act as antioxidants, antifungals, anti-infectives and antiseptics. Polyphenols are the red, blue and purple pigments found in fruits, vegetables, tea and herbs are due to their polyphenol content. They are considered to have antihistaminic, anti-inflammatory, antioxidant, anti-clotting, anticancer, antitumor and cardiovascular effects (Zimmerman 2000). Isoflavones from soy products and red clover have weak estrogenic activity and accordingly are known as phytoestrogens. Isoflavones have been widely recognized as cardioprotective, prompting the U.S. Food and Drug Administration to allow a soy protein health claim (minimum 6.25 g daily) for cardiovascular health as part of a heart-healthy diet. Soy protein also protects against some cancers and relieves menstrual, menopausal symptoms, and has been shown to reverse osteoporosis (Platzman 1999; Zimmerman 2000).
Phytochemicals in the Organic Acids and Polysaccharides group, include esters and lactones, are small to large complex carbon compounds found in grains, herbs, teas, a few vegetables and some fruits. These compounds act primarily as antioxidants, cancer preventives, liver protectants and inflammatory mediators (Zimmerman 2000).
Phytochemical lipids include unsaturated fatty acids, oils, fat-soluble vitamins and fatty acid esters. This group of phytochemicals on cellular membranes, thus affecting signaling, transport and receptor function. Some also act as enzyme cofactors and are antioxidants. The group includes isoprenoids; Vitamin E is the best-known isoprenoids. Vitamin E's primary function is to protect the phospholipid layers in membranes from free radical damage and facilitate receptor function. Vitamin E collaborates in a network with other antioxidants in a system of electron shuffling that inactivates free radicals while boosting the antioxidant power of individual cycle participants (Platzman 1999). Vitamin E appears to have tumor-inhibiting properties against breast cancer cells and lower cholesterol levels (Zimmerman 2000). Alpha-linolenic fatty acids reduce inflammation and platelet aggregation and modulating immune response. These activities protect against cardiovascular disease, cancer and many other forms of chronic disease (Platzman 1999). Docosahexaenoic acid is an integral component of brain membranes. It has been effective in reducing disorders such as schizophrenia, depression and attention deficits. Phytosterols occur in most plant species, with significant amounts found in the seeds of green and yellow vegetables. They reduce dietary cholesterol absorption, through a mechanism of competitive uptake in the digestive system and perhaps through reduction of cholesterol synthesis in the body (Platzman 1999; Zimmerman 2000).
Americans spend approximately $2 to 2.5 billion a year on vitamin/mineral supplements with the expectation that supplement consumption will ensure optimal health (American Dietetic Association 1999). Consumption of supplements containing phytochemicals will only provide selected components in a concentrated form, not the diversity of compounds that occur naturally in foods. It is important to continue the effort to encourage a balanced diet based on the principles of the Food Guide Pyramid and increased fruit, vegetable, and grain consumption to acquire the benefits of phytochemicals versus simply ingesting a pill containing these substances (American Dietetic Association 1999).
It is important for Americans to become aware of their lack of consumption of fruits, vegetables, and grains. The average American consumes only one serving of vegetables and one serving of fruit each day (American Dietetic Association 1999). Increasing the consumption of plant products in one's diet should not be difficult or time consuming. There are plenty of simple strategies for increasing dietary fruits, vegetables, and grains, including the suggestions: 1) keep fruits and vegetables (fresh, frozen, and canned) stocked and in sight, 2) Reach for juice instead of coffee or soda., 4) Add chopped fruit to cereal, yogurt, pancakes, muffins, or even a milkshake, 5) Snack on fresh chopped carrots, celery, broccoli, cauliflower, and peppers, 6) Add fresh greens, carrots, celery, parsley, tomatoes, and/or beans to your soups, 7) Store dried fruit for a quick snack at home or work (American Dietetic Association 1999). There are also several other easy methods for increasing fruits, vegetables, and grains in your lifestyle.
Never before has the focus on health benefits of commonly available goods been so strong. The philosophy that food can be health promoting beyond its nutritional value is gaining acceptance within the public arena and among the scientific community. Health is a gift that can be controlled through our own lifestyle choices that include the foods we choose to eat. Research has demonstrated the tremendous potential of phytochemicals in regard to prevention and treatment of disease. Now, it is the responsibility of not only health-care professionals, but also individuals to begin the conscientious effort of improving their diet. Even though phytochemicals are readily available in today's food supply, it is highly possible that future foods may undergo bioengineering or fortification to enhance naturally occurring phytochemical concentrations. This would make it even easier to incorporate phytochemicals in the diet. The research involving phytochemicals is promising, but with any newly discovered chemical, it is recommended that further studies be conducted.
American Dietetic Association Website. 1999. Position: Phytochemicals and functional foods. Retrieved on December 02, 2002. From the World Wide Web: http://www.eatright.org/aphytochemicals.html
Homsey, C. 1999. Functional Foods and Phytochemicals. Food Product Design Magazine.
Messina. M. 1997. Foods with "Phyte." Retrieved on December 02, 2002. From the World Wide Web: http://www.findarticles.com/cf_dls?m1041/n2_v75/19056037/p1/article.jhtml
Platzman, A. 1999. Functional Foods: Figuring Out the Facts. Food Product Design Magazine.
Zimmerman, C. N. 2000. Phytochemicals: Nutrients Whose Time Has Come. Nutrition Science News.