Supplements containing conjugated linoleic acids (in short CLA) are often used as support in reducing the level of fatty tissue. These preparations enjoy different opinions, but are rather considered to be safe and conducive not only to slim silhouette, but also health. However, it turns out that CLA has certain defects that we should bear in mind.

CLA – what is it?

Conjugated linoleic acids, also called CLA is an organic chemical compound belonging to polyunsaturated fatty acids from the family omega 6. Although this compound is mostly known as the component of slimming supplements, it is in fact also preset in food that we eat. Its natural sources are, among others: milk fat and beef.

Using CLA in supplementation

In recent years, CLA has been advertised as „fat that burns fat” and we can find an endless amount of preparations containing this fatty acids on the market of dietary supplements. It is used both by the people who are not physically active and believe in the “magic power of the capsules”, as well as sports amateurs and professional sportsmen, expecting the positive effect of the supplementation on the process of body fat reduction. Additionally, CLA is often presented as a compound that “protects from spare fat growth” in the state of energy surplus. We may also find certain mentions about the pro-health properties of this fatty acid, including positive influence on lipid and glucose balance.

CLA effectiveness in fatty tissue reduction

Unfortunately, so far the evidence for slimming properties of CLA is rather modest and based mainly on the results of experiments carried out on animals. The studies with the participation of people, in which it was proven that such effect is rather unitary, are characterized with the methodology that leaves a lot to be desired (small sample, inaccurate evaluation of body composition) and their results hardly reach the threshold of statistical significance. In fact, the only study that is worth attention and may demonstrate an interesting slimming potential of CLA is the one below:
http://www.nature.com/ijo/journal/v31/n3/full/0803437a.html
In the study lasting half a year, 40 healthy overweight people took part. The participants were divided into two groups: the first group received CLA (3,2g) and the other group received placebo. Finally, the intervention group lost 1 kg of excess fat more that the control group. Maybe this effect is not knockout, but it is worth noting. However, it is also worth knowing that when we want to evaluate the potential of a substance and its influence on the human organism, sometimes more trials than one are needed. In the meantime, the above observed results did not find confirmation in other trials, which – importantly – may be considered more trustworthy at least for the following reasons:

  • they were characterized by higher number of participants,

  • lasted longer than half a year.

The example of such a study, in which the supplementation with conjugated linoleic acids did not bring any positive results as for the changes in body mass and composition is the following:
http://ajcn.nutrition.org/content/83/3/606.long
In this research 122 people took part, who were divided into two groups (placebo and CLA at the dose of 3,4g a day). The study lasted one year and after this time no changes in the body mass and composition between the intervention and control groups were noticed.

For a change, there are also even more numerous studies, where the effects noted while using the supplement containing CLA were at least satisfying:

http://ajcn.nutrition.org/content/79/6/1118.full.pdf

Thorough data analysis

Looking for “scientific evidence” it is always worth remembering that systematic analyses of available research, i.e. the works based on analyzing a few or even several dozen various studies are more valuable than single experiments. We should note that in case of CLA we have such publications available, where authors based their conclusions on the precise analysis of the results of many trials with the use of the discussed substance. It turned out that CLA not only fails to support obesity treatment and the work on our body, but also has certain defects, that are reflected in the general metabolic health.

Dark sides of CLA

Unfortunately, there are a lot of arguments proving that CLA not only doesn’t have to support the work on our silhouette, but also – it is not so friendly to our health, as colorful slogans say. Norwegian researchers: dr. Haugen and dr. Alexander as early as in the year 2004 analyzed the available literature (based on the results of randomized clinical research with the use of placebo) regarding the influence of CLA supplementation on body mass, composition and general health. In their conclusions, the researchers found that there is no evidence that CLA supports slimming and also they paid attention to the fact that this compound may negatively influence lipid balance and insulin sensitivity! The abstract of the quoted paper is available here:

http://www.ncbi.nlm.nih.gov/pubmed/15586185
The original text is unfortunately available only in the Norwegian language:

http://tidsskriftet.no/article/1110144

More similar cases

The above cited work is not the only literature review that critically evaluated the validity of CLA use as support of losing weight and not the only one that demonstrated the potential dangers stemming from supplementation, which is shown in the below example:

http://www.tandfonline.com/doi/abs/10.1080/10408390600723953?journalCode=bfsn20
Negative influence of CLA supplementation on the endothelium functions has also received its own study. The abstract of the paper is available after clicking the link:

http://atvb.ahajournals.org/content/26/2/307.long
However, the influence of conjugated linoleic acids on lipid profile is the most pronounced, especially on the level of triglycerides. Such effect was noted in a few different studies. The author of the present article also noted it in his professional work.

More up-to-date perspective

The above cited publications today may seem quite old, as they are 10 years old – for such a period of time a lot might have happened in science. It should be borne in mind, however, that as for the verification of the influence of CLA supplementation on body mass and composition as well as – health, little has changed in fact. In more up-to-date studies, the attention is still paid to the fact, that there are certain premises to claim that CLA has slimming potential, but the results of the studies are ambiguous and there are some reasons to believe that the above mentioned fatty acid may negatively influence lipid balance, insulin sensitivity and epithelium functions. Such conclusions appear among others in this paper:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4574006/
As a curiosity, it is also worth reading the below paper, in which the authors relate to the question of the discrepancy between the results of research with the use of CLA:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4429457/

A few words at the end

The discrepancies in the results of the studies and the lack of consensus as for the influence of CLA supplementation on health and silhouette certainly are depressing, but they also may constitute a certain premise to draw final conclusions. We surely cannot say that the positive influence of CLA supplementation on body mass and composition has been proven. Unfortunately it is a compound of dubious effectiveness. Similarly, we cannot unequivocally conclude that using CLA is beneficial to health. Moreover, we may not even assume that it is totally safe. There are certain reasons to claim that, at least in certain cases, CLA supplementation may cause the increase of triglycerides level and LDL level as well as the decrease of HDL and sensitivity to insulin. People looking for sure and safe ways to fight with the excess of fatty tissue should think carefully whether CLA is the means they need.

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