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2127105 
Journal Article 
CONJUGATED LINOLEIC-ACID - AN ANTICARCINOGENIC FATTY-ACID PRESENT IN MILK-FAT 
Parodi, PW 
1994 
Yes 
Australian Journal of Dairy Technology
ISSN: 0004-9433 
49 
2 
93-97 
WOS:A1994PZ95300008 
Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of linoleic acid containing conjugated unsaturation. The cis-9, trans-11-octadecadienoic acid isomer is produced in ruminant animals as a first intermediate in the biohydrogenation of dietary linoleic acid by a linoleic acid isomerase from the rumen bacteria Butyrivibrio fibrisolvens. CLA has been shown to inhibit initiation of mouse skin carcinogenesis by 7,12-dimethyl-benz[a]anthracene (DMBA), mouse forestomach neoplasia induced by benzo[a]pyrene and rat mammary tumorgenesis induced by DMBA. Furthermore, CLA was shown to be cytotoxic to human malignant melanoma, colorectal and breast cancer cell lines in vitro. Cis-9, trans-11-octadecadienoic acid was the only CLA isomer incorporated into phospholipids of mouse forestomach and rat mammary tumors and is considered to be the biologically active factor. The mechanism whereby CLA exerts its anticarcinogenic activity is still uncertain. However, it has been found to modulate the activity of cytochrome P450 and reduce the induction of ornithine decarboxylase and protein kinase C, known tumor production indicators, and possibly inhibit protein and nucleotide biosynthesis. Some of the anti-carcinogenic properties of CLA may be due to its effective antioxidant properties. Dairy products are the richest dietary sources of CLA, depending upon pasture conditions, milk fat may contain up to 30 mg/g fat and is predominantly the biologically active cis-9, trans-11-isomer. In general, fat from meat of ruminant animals contains more CLA than fat from non-ruminants who may obtain their CLA by dietary means and some bacterial isomerism of linoleic acid. Vegetable oils and margarines only contain small amounts of CLA. CLA is present in the tissue and body fluid of humans and blood serum levels can be increased by diets rich in CLA.