Conjugated Linoleic Acid (CLA)
This fatty acid may reduce body fat, stabilize blood sugar levels, and help protect your heart

By Victoria Dolby Toews, MPH

What it is
Conjugated linoleic acid (CLA) is a naturally occurring fat found in meat and dairy products. “Conjugated” refers to CLA’s unique structure in which two double bonds are separated by a single bond. This structure is not found in standard linoleic acid. CLA takes many forms, depending on the exact location of these double bonds, but the two most common are “c-9, t-11” CLA and “t-10, c-12” CLA. For now, CLA is available only in nutritional supplements as a mixture of the two forms, usually in a 50/50 ratio.

Where it comes from
Although hamburgers and milkshakes are not where you usually think to look for the latest health-promoting nutrient, that’s where you’ll find CLA, which is formed in the gut of ruminant animals (cows, goats, sheep, and deer). Bacteria that live in our digestive systems also make trace amounts of CLA. Dietary CLA supplements are not purified from animal foods, but instead are made from more economical vegetable oil.

Why it’s used
CLA is most often used for reducing fat and toning muscle. It can also be used to help reduce the risk of breast, colon, and prostate cancers; to stave off atherosclerosis; and to lower blood sugar in diabetics.

How it works
CLA has been shown to crank up calorie burning, a big plus for dieters. It does this by partially blocking the body’s ability to store fat and causing fat cells to die through a process called apoptosis, or programmed cell death. It may also boost some antioxidant activity, which is beneficial in thwarting cancer, heart disease, and diabetes. CLA’s apoptosis function might also be useful for stopping tumor growth.

Scientific support
The jury remains out on—and perplexed by—this supplement. On the one hand, a robust body of research on animals clearly documents CLA’s ability to lessen body fat and increase muscle mass in numerous species. But the human research has been inconsistent. Although some studies find that overweight people taking CLA lose fat and gain muscle, other studies have not found CLA to be at all beneficial.

In animal-based research, CLA has also shown very promising anticancer activity for breast, prostate, and colon cancers (Journal of Nutrition, 2002, vol. 132, no. 10). The research also is encouraging for heart protection and diabetes (British Journal of Nutrition, 2002, vol. 88, no. 3).

The most common amount of CLA used in human research is 3 to 4 grams per day. Some of the animal-based research has used amounts equivalent to ten to 50 times greater than that recommended for humans, leading some researchers to contend that this difference accounts for the conflicting data between animal and human research. Most CLA supplements are softgels, with each pill providing 500 to 1,000 mg of CLA.

If you were to take 3 grams of CLA per day, the monthly cost would be about $26.

Side effects
Few side effects have been reported by those taking CLA, except isolated reports of gastrointestinal upset. Breast-feeding moms should not take this supplement because it has been shown to lower the fat content of breast milk (Lipids, 2002, vol. 37, no. 2).

It’s harder than ever to get CLA from the average diet because changes in animal husbandry practices have led inadvertently to less CLA in food. For example, most milk cows are now provided with feed, yet cows that graze in fields have up to 500 percent more CLA in their milk.

Victoria Dolby Toews, MPH, is the author of the User’s Guide to Glucosamine and Chondroitin (Basic Health Publications, 2002).