Conjugated linoleic acid, in plain terms.

Quick answer. CLA stands for conjugated linoleic acid. A 2024 review in Heliyon defines it as "a general term for all the geometric and positional isomers of linoleic acid": the same 18-carbon fatty acid, with its two double bonds rearranged. It is formed naturally in the stomachs of cows, sheep and goats, so it is found mainly in milk, dairy foods, beef and lamb. Immufix contains 365mg per 25g scoop. No health claim for CLA is authorised in Great Britain, and we make none.

What is CLA (conjugated linoleic acid)?

CLA is a group of fatty acids. Linoleic acid, the parent, is a fatty acid with 18 carbon atoms and two double bonds. In ordinary linoleic acid those two double bonds are separated by a single carbon. In CLA they sit next to each other, separated by one single bond. That arrangement is what chemists call "conjugated", and it gives the group its name.

The double bonds can sit in different positions along the chain, and each one can face either way (cis or trans). Each combination is a separate isomer. The Heliyon review counts "about 28 known isomers of CLA". Two of them dominate: cis-9, trans-11 CLA and trans-10, cis-12 CLA, which the review says represent "approximately 85 % and 10 %, respectively, of all the naturally occurring CLA isomers".

Where does CLA come from in food?

Mostly from grazing animals. The Heliyon review states that "CLA was discovered in ruminants and the main dietary sources of CLA are ruminant driven food products". Ruminants are animals that digest grass in a rumen: cows, sheep and goats.

It forms during digestion. In the review's words, "CLA isomers are synthesized in the rumen as intermediates in the biohydrogenation of dietary linoleic acid to stearic acid." Bacteria in the rumen convert the unsaturated fats in grass and feed into saturated ones, and CLA is one of the steps along the way. Some of it passes into the animal's milk and meat.

That makes the main food sources:

• Milk and dairy foods: milk, butter, cheese, cream and yogurt from cows, sheep and goats.
• Meat from ruminants: beef and lamb.

Because CLA travels with the fat, lower-fat versions of these foods contain less. The amounts are small. The review notes that "the concentrations of CLA in dairy foods are relatively low, less than 10 mg CLA/g fat". It also reports that the CLA content of milk changes with what the animal eats, rising when cows are given more oilseeds or more fresh grass.

How much CLA do people eat?

Not much, by weight. The Heliyon review summarises earlier estimates: average intakes in the USA of 176mg a day for men and 104mg a day for women, and an average intake in the UK of 97.5mg a day.

The 365mg in a scoop of Immufix is about 3.7 times that UK estimate, and about one eighth of the 3g a day used in the EFSA assessment described below (both calculated).

How is CLA made for supplements?

CLA in supplements is usually supplied as a CLA-rich oil. Unlike the CLA in milk, which is mostly the cis-9, trans-11 form, these oils contain the two main isomers in roughly equal amounts.

The European Food Safety Authority (EFSA) assessed two such oils as novel food ingredients. Its 2012 statement describes them as consisting "of approximately 80% of the two CLA isomers" cis-9, trans-11 and trans-10, cis-12, in a 1:1 ratio. The applicants suggested daily intakes of 3g and 3.5g of CLA.

EFSA's conclusion was that the safety of those oils "has been established for the proposed uses and daily doses for up to six months", and that "The safety of CLA consumption for periods longer than six months has not been established under the proposed conditions of use." That assessment was made at 3g to 3.5g a day. The amount in Immufix is 365mg. If you have questions about any supplement and your own health, ask your GP or pharmacist.

Is CLA a trans fat?

Not under UK labelling law, even though the two main CLA isomers each contain one trans double bond. Annex I of Regulation (EU) No 1169/2011, which still applies in Great Britain, defines the term like this: "'trans fat' means fatty acids with at least one non-conjugated (namely interrupted by at least one methylene group) carbon-carbon double bond in the trans configuration".

The key word is "non-conjugated". CLA's double bonds are conjugated by definition, so CLA falls outside the legal meaning of trans fat on a food label.

Does CLA have an authorised health claim?

No. CLA supplements are often marketed with claims, but every CLA entry on the GB nutrition and health claims register has the status "Non-authorised". CLA also has no nutrient reference value, so a label shows its amount with no percentage beside it. Our guide to what an authorised health claim is explains how the register works.

That is why the Immufix label lists CLA at 365mg and says nothing about what it does. We describe it, and we leave it there.

Where Immufix fits.

Immufix is one scoop (25g) in around 200ml of water, once a day. Each scoop contains 365mg of CLA, alongside the vitamins, minerals and other ingredients declared on the label. The claims on our pack belong to the vitamins and minerals. Vitamin E, zinc and selenium contribute to the protection of cells from oxidative stress. Magnesium contributes to normal muscle function. The full label, with every amount, is on the science page, and our guide on how to read a supplement label explains the rest.

The short version.

• CLA, conjugated linoleic acid, is the name for the isomers of linoleic acid whose two double bonds sit side by side. About 28 are known.
• It forms in the rumen of cows, sheep and goats, so milk, dairy foods, beef and lamb are the main food sources, at under 10mg per gram of dairy fat.
• Average UK intake from food has been estimated at 97.5mg a day. A scoop of Immufix contains 365mg.
• Under GB labelling law, CLA is not counted as trans fat, because its double bonds are conjugated.
• No health claim for CLA is authorised in Great Britain, and Immufix makes none.

Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. If you have a medical condition, are pregnant, breastfeeding or taking medication, speak to your GP or pharmacist before taking any food supplement.