Conjugated linoleic acid (CLA), is the broader term used to describe a mixture of different forms of linoleic acid. Discovered by chance in 1978 by Michael W. Pariza, CLA naturally occurs in small amounts in the meat and dairy products of ruminant animals; that is, animals that chew their cud, such as cows, goats, and sheep, among others. Though research of CLA has yielded conflicting findings, early studies have suggested some potential health benefits related to cancer, heart disease, diabetes, kidney disease, bone density, body building, and obesity.
CLA cannot be produced in great quantity by the human body. Instead, people obtain this naturally-occurring fat from dairy animals that have the ability to convert linoleic acid from plant material into CLA because of microorganism activity in the rumen. As a result of a few initial studies on the health benefits of CLA, particularly the effect CLA may have on fat storage, people have started using man-made forms of CLA as a supplement to their diet.
Following its discovery, other studies have been conducted to examine the beneficial effects of CLA on cancer, immune functions, and atherosclerosis. A variety of antioxidant and anti-tumour properties have also been linked to CLA, and select studies on mice and rats have shown promising results in reducing tumour growth, particularly in breast, skin, and colon tumours.
Does it really reduce body fat?
What has arguably generated the most noise in the health community is the possibility that CLA may be useful in reducing body fat when implemented with a program that incorporates increased physical activity and reduced dietary caloric intake.
Some studies show that taking 1.8 to 6.8 grams of CLA daily decreases body fat mass, increases lean body mass, and reduces waist circumference. While CLA does not seem to have a significant effect on BMI or weight loss in general, it reduces BMI in a special subset of the population – obese, postmenopausal women with type 2 diabetes.
How CLA may have some potential benefits on obesity may be a result of decreased energy and food intakes; decreased fat storage; and increased energy expenditure, fat breakdown, and fat burning (oxidation). It is also important to note that any increase in lean muscle can also be attributed to a more efficient metabolism and an increase in the amount of calories burned. However, currently there is insufficient evidence to support the use of dietary supplement of CLA as a weight loss aid.
Generally, the doses up to 3.4 grams are well tolerated. Some of the reported side effects include throat irritation, abdominal bloating, diarrhea, and heartburn. There is also some concern regarding evidence that may suggest the use of CLA by overweight people may increase insulin resistance and may possibly increase their risk of developing diabetes.
Preliminary research on the benefits of CLA as a dietary supplement is still very limited. Its effect on reducing fat is more convincing in animal studies than in human studies. While some studies do show a positive relationship between using CLA and decreases in body fat, the overall evidence is not conclusive. Safety and toxicity levels have yet to be established, and other benefits associated with using CLA are not clearly defined. For now, using CLA as a dietary supplement is solely at the discretion of the consumer.
Brennan Robertson, Hon. B.Sc. (Nutrition)