cis-9, trans-11 CLA - A Potent Anticarcinogen Found in Milk Fat

Early research with the cis-9, trans-11 CLA isomer suggested that this compound was anticarcinogenic. Because cis-9, trans-11 CLA is the major CLA isomer found in ruminant fat, our group wanted to determine if the CLA in milk fat was active as an anticarcinogen. Using natural feed ingredients, we designed a diet that would enhance the cis-9, trans-11 CLA content of milk fat and collected the milk from cows at Cornell's Teaching an Research Farm. We then collaborated Dr. David Barbano and workers at Cornell's Food Science Department to produce butter. The result was a butter that had a CLA content eightfold greater than control butter. Bauman et al. detail specifics pertaining to the manufacture of this butter.


In collaboration with Dr. Clement Ip and researchers at the Roswell Park Cancer Institute (Buffalo, NY), the butter was used in a study of chemically-induced mammary carcinogenesis in rats. The CLA-enhanced butter was compared to a control butter and to a diet supplemented with chemically synthesized CLA. Both the CLA-enhanced butter and the chemically synthesized CLA were effective at reducing tumor formation. This study was among the first to show that a naturally occurring anticarcinogen, fed as a component of a naturally produced food was effective at reducing the development of mammary tumors in a biomedical cancer model.


Is Butter Better?

During the course of the above experiment, we observed that animals consuming the CLA-enhanced butter had a greater tissue concentration of CLA as compared to those animals receiving the chemical supplement of CLA. Milk fat contains vaccenic acid (trans-11 18:1) and our tissues contain the enzyme delta-9 desaturase that can convert vaccenic acid to cis-9, trans-11 CLA. We hypothesized that this enzyme would convert the vaccenic acid in milk fat to CLA thereby resulting in vaccenic acid also having anticarcinogenic properties.

To examine this, we again used typical feedstuffs and designed a dairy cow diet that would result in a milk fat with enhanced vaccenic acid (VA) and CLA content. Milk was collected and processed to produce a VA/CLA enhanced butter and in this case, vaccenic acid and cis-9, trans-11 CLA represented about 20% of total milk fatty acids.



In the experiment, diets were formulated to have varying amounts of VA and CLA by changing the amount of control and high CLA butter used, as well as adding a small amount of synthetic CLA. Diets A through D contained the same amount of vaccenic acid (trans-11 18:1) with small increases in the CLA content of the diet. While diets E, F, and G were matched with diets B, C, and D respectively for CLA content and had greater amounts of vaccenic acid. Therefore, differences observed between diets B and E, or C and F, or D and G would be due to the increased amount of vaccenic acid provided by the diet.





Comparing diets with identical concentrations of cis-9, trans-11 CLA and increased amounts of trans-11 18:1, we observed that mammary tissue concentrations of cis-9, trans-11 were significantly increased.





Corl et al. were able to show that animals with increased tissue concentrations of CLA also had a decreased incidence of tumors. VA was used as a substrate to produce cis-9, trans-11 CLA and there was a reduction in tumor numbers. It is possible that trans-11 18:1 itself was anticarcinogenic, however, it is more likely that the reduction in tumor numbers was the result of increased tissue CLA produced from VA. The answer to this was recently determined by Lock et al. who determined that vaccenic acid is anticarcinogenic due to its conversion to cis-9, trans-11 CLA via delta-9 desaturase.



Data from these and other studies have lead the National Academy of Sciences to state that "...CLA is the only fatty acid shown unequivocally to inhibit carcinogenesis in experimental animals." Recently consumer awareness of functional foods has increased. A functional food is any food or food ingredient that may provide a health benefit beyond the traditional nutrients it contains. Conjugated linoleic acid and vaccenic acid are microcomponents that impart functional food characteristics to dairy products. Therefore a market for CLA-enriched dairy products may exist and should be explored further. Our group remains involved with continuing research on the effects of CLA in cancer models and have branched off to look at the effects of a high CLA butter in an atherosclerosis model. We are also involved in on going research efforts to find feeding/management practices that will elevate and maintain cis-9, trans-11 CLA levels in milk fat.


Questions regarding content of these pages, contact Dr. Dale Bauman

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