Conjugated Linoleic Acid

It’s only natural

In 1978, Michael Pariza, Ph.D., director and chair, Wisconsin distinguished professor, food microbiology and toxicology, University of Wisconsin, Madison, investigated the potential anticarcinogenic properties of hamburger. He isolated and during the next nine years identified the substance known as CLA, publishing his results in 1987 in Carcinogenesis. Today, hundreds of published papers discuss CLA’s various forms and potential health benefits.

This free fatty acid occurs in different isomeric forms, depending on the placement of double bonds between carbon atoms. The two varieties of CLA most widely studied are the cis-9 trans-11 (c9t11) and trans-10 cis-12 (t10c12) isomers.

Commercial CLA is commonly derived from safflowers and contains approximately a 50/50 mixture of c9t11 and t10c12 isomers with both di- and triglyceride forms available.

Playing with the numbers

CLA occurs naturally in dairy or animal products, with the highest concentrations in products from ruminant animals, at a ratio skewed toward a predominance of c9t11 isomers.

Although difficult to document, researchers estimate that North Americans’ average consumption level of CLA has diminished over the last 50 years from approximately 3 grams to 1 gram per day, partially because CLA levels are higher in grass-fed or range-fed animals, and feed practices have shifted to grain in the United States. However, university research discovered that by manipulating a cow’s feed, it could produce milk with five times the normal levels of CLA.

Dale Bauman, Ph.D., Liberty Hyde Bailey professor, department of animal science and division of nutritional science, Cornell University, Ithaca, NY, using CLA-enhanced milk, has produced butter with 40 to 50 mg of CLA per gram of fatty acid — 800% to 1,000% more than regular butter. Bauman is publishing a paper in The Journal of Nutrition about his findings related to the anticarcinogenic properties of the fatty acid, vaccenic acid (11-octadeconoic acid), also present in butter. He says, “In a sense, butter is better than a pill, because you’re getting both CLA and vaccenic acid.”

Dairy-derived CLA has not emerged outside of the laboratory. Various dairy-industry representatives say that it is cost-prohibitive to modify the cows’ feed, and no plans to produce CLA-enriched dairy products exist.

CLeAr health benefits

The two isomeric forms, alone and combined, pose different health benefits. The 50/50 commercial blend impacts a person’s body mass index by reducing body fat while maintaining lean muscle mass, when ingested at a recommended daily intake level of 3 grams.

The c9t11 isomer is associated with anticarcinogenic properties, possibly providing benefits in all three stages of cancer — initiation, promotion and metastasis.

Pariza says, “Both isomers appear to be equally involved in cancer inhibition, apparently via different mechanisms. The typical commercial isomer mixture appears to be the best isomer ratio for health benefits.”

Today, only supplements — not foods — utilize CLA as an ingredient. CLA producers, such as Cognis, Loders Croklaan and PharmaNutrients, are all pursuing forms of GRAS status at this time.

Currently, sales for commercially produced CLA supplements focus on body composition. Research initiatives, however, are investigating other potential health benefits. The January issue of The Journal of Nutrition discusses a human study conducted by Martha Belury, professor of human nutrition at The Ohio State University, Columbus, that revealed the t10c12 CLA isomer impacted adult-onset (type 2) diabetes by lowering the subjects’ body mass as well as blood sugar levels.