The Chemical Makeup of Conjugated Linoleic Acid
Conjugated linoleic acid (CLA) is a polyunsaturated fatty acid, an omega-6 variant derived from its parent molecule, linoleic acid. The key defining feature of its chemical structure is the presence of conjugated double bonds. While most polyunsaturated fatty acids have double bonds separated by two single bonds, CLA's double bonds are adjacent, separated by just one single bond. This unique arrangement is where the 'conjugated' part of its name comes from.
Another interesting aspect of CLA's chemistry is that it is simultaneously a cis-fat and a trans-fat. This is because at least one of its double bonds is in the cis configuration, while another is in the trans configuration, resulting in a unique molecular geometry. This is distinctly different from the industrially produced trans fats that are widely considered harmful. The naturally occurring CLA found in foods is not regulated or labeled as a trans fat by authorities like the FDA. The specific arrangement of these bonds is what creates the family of different CLA isomers, each with its own potential biological properties.
The CLA Isomers: Where Structure Defines Function
CLA is not a single compound but rather a collection of numerous isomers, with as many as 28 possibilities identified. Each isomer has the same chemical formula but a different atomic arrangement, which can significantly influence its biological activity and effects in the body. The two most prominent and extensively studied isomers are cis-9, trans-11 (c9,t11) CLA and trans-10, cis-12 (t10,c12) CLA.
- c9,t11 CLA (Rumenic Acid): This is the most abundant and naturally occurring form of CLA, making up 80-90% of the total CLA found in the fat of ruminant animals. Research suggests this isomer is largely responsible for the anti-carcinogenic properties observed in some studies.
- t10,c12 CLA: This isomer is found in smaller quantities in nature, but is a key component of synthetic CLA supplements. It has been primarily linked to anti-obesity effects, such as reducing body fat, by influencing lipid metabolism in adipocytes.
Natural vs. Supplemental CLA Composition
The most significant difference in what CLA consists of comes down to its origin: natural food versus synthetic supplements. This distinction is crucial because the isomer ratios can dramatically affect the physiological outcomes. While natural CLA is predominantly the c9,t11 isomer, supplemental CLA is created through a chemical alteration of vegetable oils, resulting in a roughly equal 50:50 blend of the c9,t11 and t10,c12 isomers.
This difference means that the effects observed from natural dietary CLA (typically lower doses and a specific isomer profile) may not directly translate to the effects of high-dose supplemental CLA (high doses and a different isomer profile). Studies have found that while supplemental CLA can offer modest fat loss benefits, it has also been associated with adverse metabolic effects, potentially due to the different isomer balance.
Where to Find CLA: Dietary Sources
For those interested in obtaining CLA naturally, dietary sources are the best option, though the amounts are modest compared to supplements. The concentration of CLA in animal products is significantly influenced by the animal's diet, with grass-fed animals producing meat and dairy richer in CLA than grain-fed animals.
Excellent natural sources of CLA include:
- Dairy Products: Grass-fed butter, milk, cheese, and yogurt are particularly rich sources.
- Ruminant Meats: Beef and lamb from grass-fed animals contain higher levels of CLA.
- Eggs: Chickens fed CLA-enriched diets produce eggs with higher CLA content.
- Mushrooms: Some mushrooms, like white button and Agaricus bisporus, are rare plant-based sources of CLA.
The Manufacturing Process of CLA Supplements
Most CLA supplements are manufactured by chemically altering linoleic acid, typically sourced from high-linoleic acid vegetable oils such as safflower oil. This process involves treating the oil with an alkali catalyst under controlled temperature and pressure to induce the isomerization of linoleic acid into CLA. This method produces the characteristic 50:50 mix of the c9,t11 and t10,c12 isomers found in most commercial supplements, which differs from the natural isomer profile.
Comparison Table: Natural vs. Supplemental CLA
| Feature | Natural Dietary CLA | Supplemental CLA |
|---|---|---|
| Primary Source | Ruminant meat and dairy (especially grass-fed) | Vegetable oils (e.g., safflower oil) |
| Isomer Profile | Predominantly cis-9, trans-11 (c9,t11) | Roughly 50:50 mix of c9,t11 and t10,c12 |
| Daily Intake Level | Modest amounts (e.g., 15-212 mg in a typical US diet) | High doses (typically 3-6 grams per day) |
| Effect on Body | Generally considered beneficial and healthy | Modest fat loss, but potential for adverse metabolic effects at high doses |
Conclusion: What Does CLA Consist of in a Nutshell
To conclude, conjugated linoleic acid is not a single substance but a family of fatty acid isomers with unique structures. What CLA consists of is ultimately a mix of these different isomers, primarily cis-9, trans-11 and trans-10, cis-12, distinguished by their conjugated double bonds. The balance of these isomers differs significantly based on whether the CLA is consumed through natural food sources, like grass-fed beef and dairy, or through synthetic supplements made from vegetable oils. This fundamental difference in composition is key to understanding CLA's varied biological effects and why its natural and supplemental forms can behave differently in the body. While natural intake is widely viewed as beneficial, high doses from supplements require a more cautious approach due to potential side effects associated with the differing isomer ratio. For a deeper dive into the health implications, consult a reputable source like the National Institutes of Health.
