Conjugated linoleic acid — The Body Composition Modulator
Conjugated linoleic acid (CLA) refers to a family of linoleic acid isomers naturally found in ruminant meat and dairy products. While primarily studied for its ability to reduce adiposity and preserve lean mass, its relevance to longevity centers on its potential to modulate lipid metabolism and inflammatory pathways.
Mechanism of Action
CLA isomers, notably cis-9, trans-11 and trans-10, cis-12, act as ligands for peroxisome proliferator-activated receptors (PPARα and PPARγ), which regulate lipid and glucose metabolism. By activating these nuclear receptors, CLA enhances fatty acid oxidation and downregulates lipogenic enzymes such as fatty acid synthase (FAS). It also influences inflammatory cascades by competing with arachidonic acid, thereby reducing the synthesis of pro-inflammatory prostaglandins and modulating NF-κB signaling. However, the trans-10, cis-12 isomer has paradoxically been shown to induce insulin resistance and oxidative stress in certain human and animal models.
Human Trial Evidence
No published human longevity trials. Human research has largely focused on body composition, with several randomized controlled trials showing modest reductions in fat mass and slight increases in lean body mass among overweight individuals. However, the clinical significance of these changes is often marginal, and some trials have reported adverse metabolic shifts, including worsened insulin sensitivity and increased markers of lipid peroxidation.
Dosing Protocol
The most commonly studied dose for body composition is 3.2 to 6.4 grams per day, typically administered in divided doses with meals. Commercial supplements usually contain a 50:50 mixture of the cis-9, trans-11 and trans-10, cis-12 isomers. Long-term optimal dosing for healthspan remains unestablished.
Safety & Contraindications
CLA is generally recognized as safe but frequently causes mild gastrointestinal side effects such as nausea, dyspepsia, and diarrhea. The trans-10, cis-12 isomer has been linked to adverse metabolic effects, including increased insulin resistance, elevated fasting glucose, and reduced HDL cholesterol. It should be used with caution, particularly in individuals with pre-existing metabolic syndrome or diabetes.