A phytochemical is any chemical produced by a plant, but more specifically refers to certain plant chemicals (such as carotenoids, lycopene, chlorophyll) that impart health benefits such as better protection from cancer. It is a non-nutrient plant chemical that has protective, disease-preventing compounds. Phytochemicals may have anticancer properties, in which case they are sometimes termed "chemopreventive agents".
Shevchuk-O'Quinn (1998) listed some of the numerous phytochemicals under scientific study as potential medicines and preventives:
- Allyl sulphides, found in garlic, onions, and other plants of the genus Allium. They may prevent stomach and colon cancers.
- Capsaicin is from peppers of the genus Capsicum and may be anti-carcinogenic.
- Conjugated linoleic acid (CLA) is a component of certain fats and oils. They may prevent atherosclerosis and certain cancers.
- Ellagic acid is a chemical found in berries, grapes, and nuts. It may be anticarcinogenic.
- Indoles, isothiocyanates and sulfurophanes (sulphur compounds) are constituents of broccoli, cabbage, and other cruciferous vegetables. They have anticarcinogenic properties.
- Isoflavones from legumes and soybeans resemble human estrogenand possibly prevents heart disease and some cancers. Genistein is a component of soy that may reduce the risk of breast cancer.
- Lignin is a noncarbohydrate dietary fibre and a major component of the cell walls of certain plants. It may aid in the prevention of breast and ovarian cancers.
- Lycopene is a red pigment that occurs in pink grapefruit, tomatoes, and watermelon. It is promoted as a prevention for cardiovascular disease and prostate cancer.
The list since 1998 has grown.
- The South African rooibos tea, for example, has the antioxidant, aspalathox. Aspalathox (rooibos tea extract, 20%) is quoted as having 375000 ORAC units/100 grams (3.5 oz). This makes it a very effective antioxidant and dietary supplement, where the USDA recommends an intake of 3000 to 5000 ORAC units/ day.
- Procyanidins, are a class of polyphenolic compounds found in several foods such as apples, almonds, barley, grapes, tea, maize, cinnamon, cocoa, peanuts, wine and strawberries. Procyanidins may act as antioxidants and modulate key biological pathways in mammals.
- Catechins, are compounds found in green tea that may reduce risk for cancer and heart disease.
Polyphenols are phytochemicals that act as antioxidants and display antiviral and anticarcinogenic properties. Flavonoids, isoflavones and ellagic acid are all polyphenols. Aspalathox has an enriched concentration of polyphenols as found in Rooibos tea. The polyphenols are unaltered and consist of the flavanoids and phenolic acids. Aspalathox has a 95% polyphenol concentration. Polyphenols in green tea include epigallocatechin (EGC) and epicatechin (EC). Polyphenols and have been shown to protect vitamin E against oxidation, to counteract increased platelet aggregation in smokers, to have anti-inflammatory properties, and to have various other health benefits.
Chocolate is a rich source of vitamins, minerals, and polyphenol antioxidants. Polyphenols and other antioxidants subdue oxidation, a process of damage to the body caused by oxygen free radicals. Oxidation has been linked to many health problems ranging from aging, cancer formation, arthritis, and even obesity! The cacao bean has one of the highest antioxidant contents of many health foods. Dark chocolate, by order of magnitude, yields a high oxygen radical absorbance capacity (ORAC).
Red wine also contains polyphenols. Bee pollen of one brand tested for total polyphenol content, showed the highest polyphenol content of any food yet tested, at 15.05 mg/g. The next highest reading was cranberries at 5.575 mg/g.
Hydroxytyrosol is the olive natural polyphenol with the highest level of free radical protection activity ever reported for any natural antioxidant compound. Olive leaf extract is known to contain a mixture of polyphenolic compounds, among them oleuropein and hydroxytyrosol, both of which are readily absorbed and bioavailable. The biological activities of olive leaf extract are mainly derived from these compounds. Polyphenolics such as genistein, epicatechins, resveratrol, or hydroxytyrosol all have antioxidant activity. Many polyphenolic compounds found in olive leaf extract are absorbed through the gastrointestinal tract, resulting in significant levels in the blood stream.
A high ORAC score indicates the ability of a food to eliminate oxidation and protect against harm from oxygen radicals. Listed in descending order, the relative antioxidant capacity (in ORAC units) of some of our most common foods are as follows: dark chocolate - 13,120; milk chocolate - 6,740; blueberries - 2,400; kale - 1,700; spinach - 1,260; broccoli florets - 890; oranges - 750; red grapes - 739; and onion - 450.
The Oxygen Radical Absorbance Capacity (ORAC) test has emerged as the standard by which science measures antioxidant activity in foods and natural supplements. Some laboratories now also measure the polyphenol content of foods and supplements. Polyphenols are called aromatic compounds, and they are biochemically characterized by the presence of six-carbon rings with an attached hydroxy (OH) group, called phenols. A molecule that contains more than one phenolic ring is called a polyphenol. Polyphenols, as a class of nutrients, include bioflavonoids, organic acids, and phenolic acids. Most of the antioxidant activity of a food is created by polyphenols. Polyphenols have been extensively studied in regard to their antioxidant activity and health-promoting biological activities. Generally, total polyphenol content is regarded as a measure of the health-promoting qualities of a whole food.