Discovered in 1978 at the University of Wisconsin, conjugated linoleic acid (CLA) is a naturally occurring fatty acid present in meat, dairy products (particularly cheddar and colby cheeses), sunflower oil, and safflower oil. It is formed when the bacteria in a cow's gut break down linoleic acid in the corn or soybeans the animal eats.
In 1996, CLA became available as a diet product derived from sunflower oil. Ads for CLA note that the nutrient may be missing from many diets (presumably since we tend to eat less meat and fewer high-fat dairy products). The product is promoted as a fat-burning, muscle-toning, energy-boosting agent and is included as a primary ingredient in many weight-loss supplements now on health food store shelves. Chromium picolinate is combined with CLA in some products.
How It Works: First of all, no one yet knows how, or if, CLA really exerts a fat-burning effect. Researchers think that the substance may interact with cytokines, non antibody proteins that are involved in energy production and fat metabolism. They theorize that CLA somehow causes protein, carbohydrates, and fats to be used by cells for energy and muscle tissue growth, rather than to be stored as fat.
Cytokines are also involved in immunity. During an injury or illness, they signal the body to break down nonessential proteins (such as those in the skin) into amino acids, in order to manufacture antibodies and produce energy to fight the disease or injury.
In rat experiments, animals lost half their body fat and gained muscle tissue when fed the equivalent of 1 to 6 grams of CLA daily. In a human study involving CLA, twenty non-obese people (ten men and ten women) were given just over a gram of CLA or a placebo with breakfast, lunch, and dinner. They were instructed not to change their diet or exercise habits.
At the end of 3 months, the researchers measured both the weight and the body fat percentage of the study participants. Even though there was not much difference in weight loss between supplementers and non-supplementers, there was a huge difference in body fat percentage. The CLA supplementers dropped from 21.3 percent (average body fat) to an average of 17 percent. While it might not sound like much, a reduction of a few points in body fat percentage can make a huge difference in how lean and firm you look. The people taking CLA lost mostly body fat the ideal situation in any trim-down program.
Another study produced much different results. It looked into whether CLA would improve body composition (percentage of fat and muscle) and boost strength. But after twenty-eight days of supplementation and weight-training, CLA had no effect on either.
Other Benefits of CLA: While investigating carcinogens that occur in grilled meats, the researchers at the University of Wisconsin who first discovered CLA found that the fatty acid appeared to block the formation of cancer-causing substances rather than promoting them. This amazing finding led to more than a decade of intensive research on CLA's potential as a cancer-fighter. Many animal studies have since found that it suppresses mammary cancer and skin cancer.
A large-scale study conducted by Finland's National Public Health Institute, published in 1996, produced compelling evidence of CLA's anti-cancer benefit. Women who drank milk regularly for 25 years slashed their odds of getting breast cancer by 50 percent, compared with nonmilk-drinking women. The investigators zeroed in on CLA as the likely agent for the protective effect, since the fatty acid is highly concentrated in milk fat.
Animal research shows that CLA may also help prevent a wasting disease called cachexia, which occurs when the body burns up muscle to obtain energy for fighting diseases such as cancer. Cachexia compromises the survival of cancer patients. CLA has been shown to reverse muscle-wasting effects in diseased animals.
CLA is also considered to be an antioxidant. Animal studies have found that it may help clear the body of oxidized LDL cholesterol, a harmful substance that clogs arteries. Thus, CLA may help protect against heart disease, but further studies are needed to confirm this benefit.
How to Use It: Studies of CLA support a dosage of 2.5 to 5 grams a day if you are trying to lose body fat. Follow the manufacturer's recommendations for dosage.
Even though CLA shows tremendous promise, not enough is known about it to make a full judgment on its effectiveness. Still, it is worth a try if you're on a weight-reduction program.
By eating a varied diet that includes meat and dairy products in moderation, you should get adequate amounts of this nutrient. Gobbling hunks of cheese or swilling gallons of whole milk is not a good way to obtain CLA, since high-fat foods eaten in excess contribute to heart disease and other serious illnesses.