Lessons in Conjugation

Gary Piscopo, ND, LAc

Natural weight-loss products seem to offer the best of both worlds: a supplement that has the aura of being "healthy" while helping to reduce unsightly pounds. One of the latest such products is conjugated linoleic acid (CLA). CLA is derived from the omega-6 essential fatty acid linoleic acid and is found most prevalently in the dairy products and meat of animals such as cattle and sheep.

It differs from linoleic acid in two significant ways, however. First, CLA is not an essential fatty acid. Second, the term "conjugated linoleic acid" does not refer to a single molecule but a mixture of eight or more different variations of linoleic acid. These variations are called "isomers". As we will see later, the fact that CLA is a mixture of isomers is somewhat problematic.

The current favorite of numerous Internet websites, CLA is promoted as a wonder supplement that can "Melt fat away!" "Protect against aging!" and "Increase insulin sensitivity!" The picture behind the Oz-like curtain, however, is somewhat different and therefore allows for some important lessons in natural supplementation.

Lesson 1: All that glitters is not gold.

Because CLA is derived from linoleic acid, advertisements will often state that it is an essential nutrient. This is not true. And while CLA may have some potential positive effects, when ingested in its natural form it also contains trans fatty acids in its chemical structure. According to the National Academy of Sciences, trans fatty acids boost blood levels of the most unhealthy form of cholesterol -- low-density lipoprotein (LDL). They may also interfere with the production of eicosanoid hormones and cellular communication. As mentioned earlier, the fact that CLA is made up of several different isomers is problematic. It is not clear which of the many isomers are helpful, if they are valuable singly, or if they need to be combined in order to be effective. Different commercial products contain different amounts of CLA isomers, some of which may not be as effective as others.

Lesson 2: At night, all rats are gray.

Consider the following information: "A double blind, placebo controlled study showed feeding CLA resulted in a fifty-percent reduction of fatty tissue and an increase in lean muscle mass." Sounds very promising -- until you learn that the test subjects are AKR/J mice, a strain susceptible to dietary obesity.

Much of the research done on CLA has been animal research, and the research done on humans has not been as promising. Interestingly, proponents of CLA will often cite this positive animal data but fail to report the negative results. One such result, which could be a significant concern, is that CLA has been shown to generate insulin resistant states and hepatomegaly (liver enlargement) in some animal models. If long term supplementation with CLA leads to insulin resistance in humans, it would mean that the body's ability to handle blood sugar would be impaired. This could potentially accelerate a tendency to diabetes in susceptible individuals, including obese populations to whom this supplement is often marketed.

The bottom line is that we cannot directly extrapolate human medicine from animal experiments, but if such studies are going to be cited, both positive and negative results should be mentioned.

Lesson 3: A rumor goes in one ear and out many mouths.

One prominent study from the Journal of Nutrition is often cited to boost claims that CLA " melts away fat and builds muscle!!" This study was done on human subjects and the researchers did indeed report a reduction in body fat mass as well as a trend toward increasing lean muscle mass. A careful review of the study, however, reveals that the subjects were also exposed to light or intensive exercise training during the course of the study. Thus, the researchers themselves were unable to say definitively if the results seen were due to CLA or training activities.

Lesson 4: When in Rome, talk to lots of Romans.

When confronted with a new and "marvelous" natural supplement, one way to get quality information is to talk to an expert. With a dietary supplement such as CLA, an expert would be a someone like a nutritionist, naturopathic physician, or medical provider well-versed in nutrition. Unless they work extensively with nutrition, do not assume that your medical doctor, chiropractor, or other medical provider is an expert simply because they have a medical degree.

In general, nutritional experts have been slow to adopt the use of CLA. One reason, as indicated above, is that the research in humans is confusing and contradictory. Another reason is that there are a number of alternatives for each of the conditions allegedly improved by CLA, including cancer, diabetes, weight control, and cardiovascular disease.

Health practitioners prefer to use better researched options for these conditions, such as exercise for weight management, omega 3 oils for cardiovascular disease, and a variety of antioxidants for the prevention of cancer. Also problematic from a clinical perspective is that, unlike fats such as omega-3 oils, ingesting CLA in its food-related form cannot be recommended. This is because foods high in CLA are also high in saturated fat, cholesterol, and trans fatty acids.

Finally, the use of CLA is limited by what we do not yet know about the supplement. It should be given cautiously to obese patients in the high-risk cardiovascular disease category, patient with liver disease, and individuals with either insulin resistance or type II diabetes.

Nutritional supplements have many beneficial things to offer us as long as we are prudent in the selection of such supplements. A little skepticism and a bit of investigation goes a long way in this regard. Or as the old Irish proverb reminds us: The person who wears boots does not need to mind where they place their foot.