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cis-9, trans-11 CLA has been shown to reduce the incidence of cancer tumors in a wide range of different cancer models.
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cis-9, trans-11 conjugated linoleic acid is the predominant CLA isomer found in ruminant fat including milk fat.
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Diet plays a major role in determining the milk fat levels of cis-9, trans-11 CLA, and changes in diet can result in greater than 400% differences in the CLA content of milk fat.
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Even when all cows are fed the same diet, milk fat levels of cis-9, trans-11 CLA among individual cows can vary by up to 300% within a herd.
How is cis-9, trans-11 CLA made in the cow?
Biohydrogenation of dietary fat by rumen bacteria is the key. CLA is produced as an intermediate in rumen biohydrogenation of linoleic acid present in the cows diet. A portion of the CLA in milk fat comes from that which has escaped complete biohydrogenation in the rumen. However, the majority is made by the cow herself using the desaturase enzyme and trans-11 18:1 (vaccenic acid), another fatty acid intermediate produced during rumen biohydrogenation.
Can the CLA content of milk fat be increased?
Diet plays a major role in determining the milk fat content of cis-9, trans-11 CLA. Factors increasing CLA level include altering rumen fermentation (e.g. lush pasture, high forage) and providing unsaturated fatty acids (e.g. processed plant seeds, plant oils). References by Kelly et al. provide more information about the effects of pasture and dietary fat sources on cis-9, trans-11 CLA content in milk fat. Chouinard et al. also discuss the effects of dietary fat source on CLA concentrations in milk fat.
Does milk fat from all cows have the same CLA content?
Cows within a herd fed the same diet vary by about 300% in the milk fat content of CLA. Thus, there must be a strong genetic component affecting milk fat content of cis-9, trans-11 CLA. Kelsey et al. provide more information on this topic.
More information about the research from our group in the area of cis-9, trans-11 CLA and human health can be found here.
