Cancer Prevention by Catechins, Flavonols, and Procyanidins

1. Dietary catechins, flavonols, and procyandins (PC) are found in a large variety of fruits, vegetables, tea, and other foods. Epidemiological studies have shown that the intake of a variety of fruits and vegetables has been supported by a lower risk of developing cancer. 2. Chemical studies have shown that these compounds have strong antioxidative activity in vitro and are capable of scavenging free radicals and chelating metal ions involved in the generation of free radicals. Given the proposed role of free radicals in aging and the development of many diseases, including cancer, it was hypothesized that compounds that prevent the development of free radicals might also prevent the development of related diseases. 3. Cancer prevention by dietary catechins, flavonols, and PC has been studied in many different animal models of carcinogenesis. These compounds have been shown to inhibit the development of cancer in animal models of oral, esophageal, forestomach, stomach, intestinal, colon, liver, prostate, skin, and breast cancers. 4. Tea catechins have been the most widely studied for cancer preventive activity and have been subjected to laboratory, epidemiological, and controlled clinical investigations. The results of studies in animal models of cancer suggest that tea catechins have cancer preventive activities against a broad range of cancer types. 5. Dietary flavonoids have a long history of safe dietary use, and human trials with higher doses of purified compounds have been conducted without serious adverse effects. However, several reports have recently suggested that these compounds may be potentially toxic. Therefore, caution should be exercised when recommending doses for human consumption, especially when considering concentrated or purified products.