Conjugated [kon-juh-gey-tid] linoleic [li-noh-lee-ik] acids (CLA) are a family acids found mostly in the meat and dairy products derived from ruminants. CLAs can be either cis- or trans-fats.
In 1979, researchers from the University of Wisconsin applied a beef extract to mice skin. The mice were then exposed to a strong carcinogen. When the researchers counted the number of tumors developed by the mice 16 weeks later, they found to their surprise that the mice exposed to the beef extract had 20% fewer tumors. The identity of this anticarcinogen was not discovered until almost a decade later, in 1987.
Michael Pariza, the scientist who discovered CLA, later remarked that ‘few anticarcinogens, and certainly no other known fatty acids, are as effective as CLA in inhibiting carcinogenesis in these models.’ CLA has also shown promise in treating inflammatory bowel disease, and it is also known for its body weight management properties, which include reducing body fat and increasing lean muscle mass.
Conjugated linoleic acid is both a trans fatty acid and a cis fatty acid. The cis bond causes a lower melting point and ostensibly also the observed beneficial health effects. Unlike other trans fatty acids, it may have beneficial effects on human health. CLA is conjugated, and in the United States, trans linkages in a conjugated system are not counted as trans fats for the purposes of nutritional regulations and labeling. CLA and some trans isomers of oleic acid are produced by microorganisms in the rumens of ruminants. Kangaroo meat may have the highest concentration of CLA. Food products from grass-fed ruminants (e.g. mutton and beef) are good sources of CLA, and contain much more of it than those from grain-fed animals. In fact, meat and dairy products from grass-fed animals can produce 300-500% more CLA than those of cattle fed the usual diet of 50% hay and silage, and 50% grain. Eggs are also rich in CLA, and CLA in eggs has been shown to survive the temperatures encountered during frying. Some mushrooms are rare nonanimal sources of CLA.
The Daily Omnivore 
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