Food for Health: Conjugated Linoleic Acid: Good or bad nutrient for weight loss?

Weight loss dietary supplements offer patients a faster and easier way to lose weight than caloric restriction and physical exercise. Despite concern with efficacy and safety, these products continue to be an attractive option for weight management.
The main reasons for patients decide on these kind of supplements may be the perception that they are “natural” and perhaps safe and there is no need for a prescription since they are freely sold in the supermarket.
Conjugated linoleic acids (CLAs) are a slightly altered form of the essential fatty acid linoleic, known as omega-6, with different arrangement of particles  that make up the molecule, which can be found naturally in foods like dairy products and red meat from ruminants, and in some kind of vegetable oils. It can also be commercially synthesized from linoleic acid–rich oils such as sunflower and safflower oil.
One of the most studied physiologic effects of CLA is its influence on body composition. Many animal studies have shown CLA is effective in weight loss and body fat reduction. This effect has been explained by several mechanisms of action, including decreased synthesis of fat. This information led to a growing interest in studying if CLA has the same effect in human being, but although studies have sh

own the health benefits in animal models, there is lack of evidence to support the same benefits to humans.

Nine different forms of CLA have been reported as naturally occurring in foods. The average daily intake of the major form of CLA, from the diet, in Western societies, ranges between 150 and 200 mg/d, it seems also to be endogenously formed in humans from other type of fatty acids found in dairy fat. This amount of dietary CLA intake is not enough to reach therapeutic effects, for larger doses there is a need of supplementation or CLA enriched foods (American Journal of Clinical Nutrition, 2006).
Commercial CLA supplements are largely sold with an indication for weight loss and increase lean body mass. These products are considered dietary supplements, so, they are not regulated as a medication and they can be marketed without evidence to support efficacy and safety.
Data from a recent study showed that supplementation of CLA, for a period of 8 wk, in overweight men with high level of blood lipids did not alter body weight or body composition neither blood lipid profile, which are in  agreement with other human data demonstrating a lack of effect of CLA  (Journal of  Nutrition 141: 1286–1291, 2011).
Concerning the risk of CLA use, some studies reported damage in blood vessels and increase in markers of oxidative stress, and inflammation that may cause adverse effects on cardiovascular health.
There are not yet convincing data supporting the efficacy and safety of CLA supplement in weight loss in humans. So, those who decide on CLA for weight and fat reduction must be aware and ask a health care provider to asses the risk and benefit of the use of this agent for weight management.