What is CLA

CLA Chemistry and CLA Needs in Dogs

Conjugated linoleic acid (CLA) has been getting a lot of attention as a "healthy fat" in recent years, but exactly what is CLA?

The short answer to What is CLA is: Conjugated linoleic acids are a class of conjugated isomers of linoleic acid, an essential fatty acid belonging to the omega-6 family of polyunsaturated fats.

Discovery of CLA

In 1978, Michael Pariza, a scientist at the University of Wisconsin, conducted a study examining the formation of carcinogenic mutagens in grilled ground beef during the cooking process.

The findings of mutagens in grilled meat were not new, but Pariza observed something that had not been reported in previous studies: the grilled beef also contained an unknown substance that appeared to inhibit mutagenesis.

The study concluded with the speculation that the unknown mutagenesis inhibitor may also inhibit carcinogenesis.

Almost a decade later, in 1987, Pariza identified the substance in question as conjugated linoleic acid, and confirmed that CLA did indeed exhibit anticarcinogenic activity.

CLA Chemistry

Linoleic acid, a member of the omega-6 family (the name denotes the position of the first double bond located at the sixth carbon atom from the omega end of the molecule's carbon chain), is considered an essential fatty acid.

Dogs (and humans, for that matter) must obtain it from dietary sources because their bodies are unable to synthesize it. Conjugated linoleic acid is a modified form of linoleic acid in which the two double bonds are separated by only one single bond.

What is CLA - A family of no less than 28 positional and geometric isomers of linoleic acid. Positional isomers are named according to the placement of their conjugated double bonds. For instance, 9,11 denotes that the double bonds are conjugated at carbons 9 and 11.

Other positional CLA isomers include 7,9; 8,10; 10,12; 11,13; and 12,14. Because each double bond can be in the cis or the trans position, four geometric configurations are possible for each positional isomer: cis, trans; trans, cis; trans, trans; and cis,cis.

While it's possible that several CLA isomers have biological activity, all known effects derive from just two isomers: the cis-9, trans-11 isomer (c9,t11-CLA) and the trans-10, cis-12 isomer (t10,c12-CLA).

c9,t11-CLA

The cis-9, trans-11 isomer is most abundant in food sources of CLA, while t10,c12-CLA is present to a lesser degree. The two isomers appear to have distinct effects.

While both isomers provide health benefits, most of the potentially adverse effects of CLA are associated with the trans-10, cis-12 isomer.

CLA is a trans fatty acid as well as a cis fatty acid; however, being conjugated, it does not have the health drawbacks commonly associated with trans fatty acids, and it's not identified as a trans fatty acid for food labeling and regulation purposes.

What is CLA Best Dietary Sources

Meats and especially dairy products from ruminants (cows, sheep, deer, goats, etc.) are the best sources of CLA, providing 2.3 to 19 mg of CLA per gram of fat (with 3 to 9 mg being average).

That's about 120 mg in a 4 ounce serving of meat. Lamb tends to contain more CLA than beef.

The highest CLA levels of all can be found in kangaroo meat, which delivers 38 mg of CLA per gram of fat.

While kangaroos aren't true ruminants, their digestive systems are similar, with a foregut where food is fermented. However, because kangaroo meat is exceptionally lean with just 2% fat, an identically sized serving of lamb or beef, two far fattier meats, can easily contain more CLA.

Grass-fed ruminants produce 2-5 times more CLA than their grain-fattened feedlot counterparts. The reason for this can be found in the bacterial isomerization of linoleic acid in the rumen.

When a ruminant consumes grasses or grains containing linoleic acid (LA) or alpha linoleic acid (ALA), Butyrivibrio fibrisolvens, a probiotic bacterium in the rumen, converts the LA to CLA.

However, proliferation of B. fibrisolvens is highly dependent on a favorable pH balance in the rumen. Grain consumption has been shown to lower rumen pH to a level that reduces B. fibrisolvens activity, while grass-based diets provide the ideal environment for bacterial synthesis.

Turkey is the best non-ruminant source of CLA, weighing in at 2.5 mg per gram of fat.

Other non-ruminant animal products such as pork, chicken, and eggs contain 0.6 to 0.9 mg of CLA per gram of fat, while seafood provides at best 0.3 to 0.6 mg of CLA for every gram of fat.

Nuts and vegetable oils have CLA levels ranging from 0.1 to 0.7 mg per gram of fat content. The cis-9, trans-11 isomer comprises 80-90% of the total CLA content in ruminant products, but accounts for only 38-47% of the CLA in plant foods.

Experiments involving the fortification of animal feeds with CLA are underway, so it may soon be possible to purchase animal products with significantly higher CLA concentrations.

For instance, in one such experiment, researchers were able to increase CLA content in pork from less than 0.1% to 1-6% of total body tissue.

Supplementing chicken feed with CLA has resulted in eggs containing an impressive 280 mg of CLA; that's 56 mg per gram of fat.

Cooking does not destroy CLA. In fact, one study found that cooking meats increases CLA content fourfold. While not all studies have shown increases in CLA after cooking, there is widespread consensus regarding the stability of CLA when exposed to heat. It also appears that at least some processing methods can increase CLA levels in foods.

Do Dogs Need CLA?

While dogs have a dietary requirement for linoleic acid, there is no known requirement for CLA. That said, the field of canine nutrition is constantly evolving, and there is much we do not yet know.

Even if there is no dietary requirement as such, it is possible that dogs can benefit from CLA in their diets or even from CLA supplementation.

Epidemiological studies in humans suggest that there might be a link between low dietary and serum CLA and certain types of cancer, specifically breast cancer.

At least one canine study has found that the c9,t11-CLA and t10,c12-CLA isomers "not only suppressed malignant mammary cell growth [in dogs], but also exerted inhibitory effects on tumor-associated non-malignant mammary cells."

There is evidence to suggest that CLA "has the potential to serve as an effective chemopreventive nutriceutical factor for breast cancer prevention" in humans as well as dogs.

What's less clear is how much CLA might be required to function as a cancer preventative.

One study speculated that as little as 95 mg of CLA daily—an amount easily obtained by consuming very moderate amounts of red meat or dairy products—can reduce human breast cancer rates.

Another study estimated the amount of CLA required to prevent cancer at 441 mg for women and 620 mg for men. Yet another study concluded that 3 grams a day are necessary to see health benefits such as cancer prevention.