CLA: conjugated linoleic acid

Generality

Conjugated linoleic acid, more simply called CLA, is an isomer of the more well-known linoleic acid (LA).

Linoleic acid is a polyunsaturated fatty acid belonging to the family of omega 6, characterized by a carbon skeleton of 18 atoms and two double bonds, the first of which in position 6 (see figure).

While maintaining the same carbonaceous constitution, CLA differs from linoleic acid in the position of the two double bonds; these, in particular, lie between the tenth and twelfth carbon atom or between the ninth and eleventh.

The particular chemical structure of this fatty acid defines sixteen possible isomers, but in nature there are mainly two, 9 cis - 11 trans and 10 cis - 12 trans, whose abundance is certainly related to its biological functionality.

Conjugated linoleic acid is called an essential fatty acid, as the human organism does not present the enzymes responsible for its synthesis.

These enzymes, on the other hand, belong to the rumen (stomach with digestive functions) of ruminants, where the presence of specific microorganisms is able to induce the incomplete biohydrogenation reaction necessary for its synthesis.

It can therefore easily be deduced that one of the main sources of this substance is animal meat, but above all milk and its derivatives.

However, there are other sources of CLA, such as safflower and sunflower oil, from which extraction is preferred to produce specific supplements.

In a healthy diet, the proportion of conjugated linoleic acid introduced daily with the diet was estimated at between 20 and 170 mg, much lower than that suggested by the various supplementary protocols.

Indications

Why is CLA used? What is it for?

CLA are classically attributed different biological functions, mostly observed on experimental models.

More precisely, from the first indications, in addition to the nutritional role, potential activities would emerge:

anticancer;
antithrombotic;
immunomodulatory;
antiobesigene;
antidiabetic.

However, despite the very large number of published articles, most of the documentation was obtained on in vitro or animal models, making the interpretation of the effects of a specific CLA supplementation in humans quite problematic.

To this limit others are added, deriving from the pro-inflammatory role of some isomers of this fatty acid.

Property and Effectiveness

What benefits has CLA shown during the studies?

As mentioned, most of the studies currently available in the literature describe the biological effects of CLA on experimental models.

These studies would reveal valuable functions but also noteworthy limits.

CLA and cancer

The anticarcinogenic action would seem to be accomplished through the modulation of the apoptotic signal, both on in vitro models and on animal models. This activity has been observed against neoplastic diseases affecting the breast, lung and intestine.

Significant clinical trials that show this ability also in humans are lacking today.

CLA and cardiovascular health

The antithrombotic action would seem to be guaranteed by the ability of the CLA to modulate the synthesis of arachidonic acid and pro-inflammatory molecules, such as thromboxanes, leukotrienes and some prostaglandins.

Thanks to this activity, the CLA would present an important protective action against the cardiovascular system.

CLA and immunity

The immunomodulatory action of CLA, also active on healthy individuals, would facilitate the reduction of immunoglobulin concentrations responsible for allergic reactions (IgE), while increasing the effectiveness of the specific immune response.

This would result, on the one hand, in a lower risk of autoimmune reactions, and on the other hand in a more effective protection against potential pathogens.

CLA and body composition

CLA has gained a prominent place in sports dietetics, due to its potential improvement role towards body composition.

Going into more detail, an important distribution action would have been observed, responsible for a significant decrease in fat mass levels in favor of the muscular one.

This action, particularly evident on animal models, where the dosages used far exceed those applicable to humans - is drastically reduced on humans, where the weight loss induced by CLA supplementation would be around 90 g / week.

Limits of integration with CLA

Despite the potential effects of conjugated linoleic acid, the scientific literature and leading world experts still seem skeptical in suggesting its use as a food supplement.

This widespread perplexity arises both from the observation of experimental data, with a significant reduction in efficacy passing from laboratory animals to humans, and from the presence of studies that warn of potential but important side effects:

Increase in inflammatory biomarkers (reactive c protein and white blood cells), potentially dangerous for some types of diseases;
Increase in insulin resistance: this effect, which seems to be more pronounced for the T10, C12 isomer, drops significantly when an evenly composed mixture is used.
Increased oxidative stress: increased lipoperoxidation levels.
Dyslipidemic effect: associated with the T10 isomer, C12, takes the form of a reduction in plasma HDL cholesterol levels, with an increase in LDL and an increase in hepatic lipid concentration.

Consequently,

The presence of these evidences, even if attributable mainly to one of the two isomers present in nature;
The absence of standardized and controlled extraction protocols that can reassure the user on the correct racemic composition between the two isomers;
The absence of benefits so important as to justify some risks

definitely limit the spread of CLA among food supplements.

Doses and method of use

How to use the CLA

The dosage proposed by the various studies in the literature foresees a series of values between 2 grams and 6.4 grams of CLA per day, even if the most replicated one, which seems to give better results, is around 3.4 grams.

Generally, the maximum intake of 0.1 g / kg per day should not be exceeded.

Given the chemical structure, it would be preferable to take the CLA during meals, in order to improve absorption, dividing the total daily quota into at least 3 assumptions, compatibly with the dosages proposed by the various manufacturers.

Side effects

The use of CLA is generally safe and well tolerated, although at doses higher than 2 grams per day gastroenteric reactions may occur, such as nausea and abdominal pain.

Contraindications

When CLA should not be used

The use of CLA is contraindicated in cases of renal or hepatic disease, cardiovascular disease and / or hypertension, and in case of hypersensitivity to the active ingredient.