CLA (Conjugated Linoleic Acid): Explained

CLA (conjugated linoleic acid) is a naturally occurring fatty acid found above all in the fat of ruminants – in milk, butter, cheese and in the meat of cattle and lamb. As a food supplement it is usually obtained from safflower oil and offered in softgel capsules. In the EU, no health claims are currently approved for CLA; we therefore describe it factually, but thoroughly.

When you scan the sports or fitness shelf for “fat burners”, CLA is almost guaranteed to be among them. That makes you curious – and sceptical. So here we explain honestly what CLA really is: a rather fascinating fatty acid that only forms in the belly of a cow. What it can and cannot do, we set out clearly.

The most important points at a glance

• What: CLA is a family of isomers (variants) of conjugated linoleic acid – a special form of the omega-6 fatty acid linoleic acid.
• Origin: forms in the rumen of ruminants; accumulates in milk and meat – especially with pasture farming.
• As a supplement: usually softgel capsules, technically obtained from safflower oil (safflower).
• Main isomers: c9,t11 (rumenic acid) and t10,c12.
• Assessment: no approved health claims – a neutral, factual description, no promise of effect on weight or body fat.

What exactly is CLA – and what does “conjugated” mean?

Linoleic acid is one of the best-known omega-6 fatty acids and is found in many vegetable oils. CLA is its structurally rearranged relative: two double bonds in the molecule no longer sit apart as usual, but directly next to each other. It is precisely this arrangement that chemists call conjugated. Sounds like a detail, but it makes all the difference – because from this one basic structure several isomers arise, which differ in the position and geometry of the double bonds and behave differently in biochemical terms.

The two most important are the isomer c9,t11 (also rumenic acid, the one dominant in nature) and t10,c12. Remember these two abbreviations – they appear on almost every reputable CLA label, and anyone who knows them reads a product far more confidently.

The clever part: CLA only forms in the cow's rumen

The most exciting thing about CLA is how it comes about. It is not present in nature ready-made, but is only “built” – and by bacteria at that. In the rumen of ruminants (the large forestomach of cow, sheep and goat) live countless microbes that convert the plant fatty acids from the feed. In this process, biohydrogenation, CLA arises as an intermediate stage. It then migrates into the milk fat and the body fat of the animal.

That explains two things at once: why, of all things, dairy products and ruminant meat are the natural main sources – and why feeding is so decisive. Animals with plenty of fresh pasture grass supply the raw materials in abundance, and the CLA content in their fat is correspondingly higher.

Where is CLA found? An overview of natural sources

So anyone who values provenance has a real lever: pasture farming with plenty of grass is reflected directly in the fatty acid profile. That is a factual observation about food quality – not a health-related promise of effect.

CLA as a food supplement: forms, origin, isomers

Because purely vegetable oils contain hardly any CLA, the CLA for supplements is produced technically from safflower oil (safflower) and in the process converted into the conjugated form. It is almost always offered as an oily softgel capsule. On the label you will usually find the total CLA content and the isomer ratio – often a roughly equal mixture of c9,t11 and t10,c12.

Why many people reach for CLA

CLA supplements have their firm home in the sports and fitness world. The typical situation: someone is in a conscious dietary phase, trains regularly and would like to accompany their plan with an additional fatty acid. The context in which someone uses CLA is individual and part of a personal nutrition plan. We describe this context of use – that is, what people do – and expressly derive from it no promise of effect on weight or body fat.

What research is investigating

Established and textbook knowledge is: CLA is a naturally occurring group of fatty acid isomers that forms in the rumen of ruminants and accumulates in milk and meat. That is sound biochemistry and food science.

Beyond that, the individual CLA isomers are the subject of numerous investigations – often in connection with fat metabolism and body composition. It is interesting that the isomers are considered separately here, because they behave differently in biochemical terms. To be honest: the body of evidence on CLA supplements is mixed and controversially discussed. An established effect claim that could be formulated for a food supplement does not follow from this.

Honestly assessed: what is clear and what remains open

What CLA is and how it forms is crystal clear – it can be traced right back to the bacterium in the rumen. What a CLA supplement concretely does in everyday life, by contrast, is not conclusively clarified and is the subject of ongoing research. Anyone who uses CLA should see it for what it is: one special natural fatty acid among many. On topics around weight, metabolism or if you take medication or are pregnant, the rule is: please clarify with a doctor.

CLA in the context of the large fatty acid family

To place CLA in context, it helps to look at the big picture. Fatty acids differ above all in whether and how many double bonds they carry:

An important difference worth knowing: for EPA and DHA there are approved claims (for example on normal heart function from 250 mg daily) – for CLA there are as yet no such approved claims. That is exactly why we describe CLA neutrally.

Quality & intake: what you can look out for

• Form: softgel capsules (oily fatty acid); intake usually takes place with a meal.
• Origin: traceably obtained from safflower oil.
• Declaration: stated CLA content and isomer ratio (c9,t11 / t10,c12).
• Purity: lab-tested, without unnecessary additives.
• Storage: store fatty acids cool and protected from light to avoid oxidation.
• Dose: since there is no approved effective dose, the product's recommended intake is the guide.

Suitable products & further guides from Scheunengut

You will find fatty acids and products around sport and metabolism in Sport & Fitness as well as in Metabolism & Weight. To compare other fatty acids, our guides are worthwhile: Omega-3: how much a day?, Linseed oil vs. fish oil and EPA & DHA explained. Around nutrition in training, fitting reads are Nutrients on a calorie-reduced diet, Nutrients for occasional athletes and Nutrients for strength training & muscle building.

Frequently asked questions (FAQ)

Is CLA vegan?

Natural CLA comes from the fat of ruminants and is therefore of animal origin. CLA supplements, by contrast, are almost always obtained technically from safflower oil (safflower) and are therefore often suitable for a vegan diet – check the labelling on the packaging.

What do the abbreviations c9,t11 and t10,c12 on the label mean?

These are the two most important CLA isomers. c9,t11 (rumenic acid) is the isomer that naturally dominates in milk and meat, t10,c12 is usually also included in supplements. They differ in the position of their double bonds and are considered separately in research.

Can I also simply obtain CLA through my diet?

Yes. Milk, butter, cheese as well as beef and lamb naturally contain CLA – especially from animals kept on pasture with plenty of fresh grass. Anyone who values provenance has the greatest lever here.

When is the best time to take CLA?

Since CLA is an oily fatty acid, it is usually taken with a meal. There is no approved effective dose, so the recommended intake of the respective product is the right guide.