Inhibition of neoplasia by minor dietary constituents
Wattenberg, L.W.
Cancer Research 43(5 Suppl): 2448s-2453s
1983
ISSN/ISBN: 0008-5472 PMID: 6403236 Document Number: 210774
Food contains a large number of inhibitors of carcinogenesis, including phenols, indoles, aromatic isothiocyanates, methylated flavones, coumarins, plant sterols, selenium salts, protease inhibitors, ascorbic acid, tocopherols, retinol and carotenes. The diversity and widespread occurrence of those compounds in food make it almost impossible to eat a diet which does not contain inhibitors of carcinogenesis. Inhibitors can be classified as to the time in the carcinogenic process at which they act. Some prevent formation of carcinogens. Others, termed "blocking agents", prevent carcinogens from reaching or reacting with critical target sites. A third group called "suppressing agents" are effective when taken after carcinogens. Some compounds inhibit at more than one time point. Blocking agents, in particular those which act by increasing host detoxification systems, are examined. Many blocking agents produce a coordinated increase of multiple detoxification systems. Two distinctive patterns termed type A and type B have been identified. One enzyme system commonly induced by blocking agents is glutathione S-transferase. On the basis of that information, induction of glutathione S-transferase activity is being used to detect the presence of blocking agents in complex natural products. Green coffee beans induce increased glutathione-S-transferase activity and inhibit mammary neoplasia in rats resulting from treatment with 7,12-dimethylbenz(a)anthracene. Two potent inducers of increased glutathione S-transferase activity have been isolated from green coffee beans. These are kahweol palmitate and cafestol palmitate. Several plant materials inhibited carcinogenesis when given after carcinogen exposure. The identification and further investigation of inhibitors present in food are of importance so that their impact on the occurrence of neoplasia in man can be ascertained.