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Conjugated Linoleic Acid

CLA are fatty acids that acts on a system known as PPAR to induce fat loss. At least, that is what the theory says. CLA too weakly affects PPAR receptors to really induce fat loss in an appreciable amount. TTA appears more promising.

Our evidence-based analysis on conjugated linoleic acid features 167 unique references to scientific papers.

Kamal Patel
Research analysis led by .
Reviewed by
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Last Updated:

Summary of Conjugated Linoleic Acid

Primary information, health benefits, side effects, usage, and other important details

Conjugated Linoleic Acid, or CLA, is a term used to refer to a mixture of fatty acids that have the general structure of linoleic acid (18 carbons in length, 2 double bonds) where the double bonds exist two carbons away from each other; they are all polyunsaturated fatty acids, and some may be trans fatty acids.

Although many exist, only two are commonly referred to. One called c9t11 (cis-9, trans-11) and the other t10c12 (trans-10, cis-12), named after what bond occurs where on the side chain.

CLA has been investigated to be a fat burner and health promoting agent due to its effect on a molecular signalling receptor family named PPAR which is related to fat burning, steroid signalling, inflammation, and glucose/lipid metabolism.

However, human studies on CLA are very unreliable and the overall effects seen with CLA are not overly potent as well as sometimes contradicting. CLA is a good research standard to investigated fatty acids and the PPAR system, but its usage as a supplement for personal goals is quite lacklustre.

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How to Take

Medical Disclaimer

Recommended dosage, active amounts, other details

Supplementation of conjugated linoleic acid (CLA) tends to be in the range of 3,200-6,400mg daily, taken with meals. This dosage assumes that approximately 70% of the product by weight is comprised of one of the two main active isomers, cis-9 trans-11 (c9t11) and trans-10 cis-12 (t10c12).

Limited studies using higher doses than the aforementioned have failed to find additional benefit, and while this could simply be due to the unreliability of CLA supplements it also means that there is no evidence that doses higher than the above are more effective.

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Human Effect Matrix

Unlocked for Examine members

The Human Effect Matrix summarizes human studies to tell you what effects Conjugated Linoleic Acid has on your body, how much evidence there is, and how strong these effects are.

Full details are available to Examine members.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
Notes
grade-a
Lean Mass
Minor Moderate See all 13 studies
Some evidence that CLA can preserve lean mass during fat loss in an obese cohort of patients, but even in this subgroup the results are highly unreliable.
grade-a
Fat Mass
- Moderate See all 20 studies
Evidence is too unreliable to conclude an inhernet effect of CLA on fat mass. There may be a context-dependent reduction in body fat and explanation for the observed variability, but at this moment in time too much evidence concludes no effect
grade-a
HDL-C
- Moderate See all 16 studies
Insufficient evidence to support significant influences on HDL-C
grade-a
Insulin Sensitivity
- High See all 12 studies
For the most part, ineffective; too unreliable to reach any conclusions in regards to the efficacy of CLA. There appears to be some manner of interaction, but both sensitization and resistance has been noted
grade-a
Weight
- High See all 22 studies
CLA is considered ineffective for weight loss to the high degree of unreliability in the results, with most evidence suggesting no effects and some sparse evidence to suggest both increases and decreases.
grade-b
Triglycerides
Minor Moderate See all 8 studies
May possible increase triglycerides, but is unreliable in doing so and not overly potent.
grade-b
Adiponectin
- High See all 3 studies
No alterations in adiponectin has been noted with CLA supplementation
grade-b
Blood Glucose
- Very High See all 9 studies
Insufficient evidence to support reliable increases in blood glucose
grade-b
C-Reactive Protein
- High See all 8 studies
For the most part, CLA is seen as ineffective.
grade-b
HbA1c
- Very High See all 3 studies
No significant reduction (or increase) in HbA1c levels following CLA supplementation
grade-b
Inflammation
- Very High See all 4 studies
Insufficient evidence to support significant changes in inflammatory status.
grade-b
Insulin
- High See all 5 studies
No significant influence on fasting insulin levels
grade-b
LDL-C
- High See all 12 studies
Insufficient evidence to support decreases of LDL-C and evidence to support no influence whatsoever.
grade-b
Liver Enzymes
- Moderate See all 8 studies
Inconsistent and unreliable effects on liver enzymes, no significant influence is thought to exist.
grade-b
Metabolic Rate
- Moderate See all 5 studies
Currently thought to be somewhat ineffective as the evidence supporting an increase are confounded with food intake whereas the evidence supporting no increase is more statistically robust.
grade-b
TNF-Alpha
- High See all 4 studies
Insufficient evidence to support changes in TNFa, a biomarker of inflammmation.
grade-c
8-isoPGF2a
Minor Very High See all 3 studies
8-isoPGF(2)a is normally a biomarker of lipid peroxidation, but CLA may be causing a false positive (as fatty acids are known to interact with the enzymes in question and other markers of lipid peroxidation are unchanged).
grade-c
Fat Oxidation
Minor - See study
May influence fat oxidation, but more evidence is required.
grade-c
Antioxidant Potential
- - See study
Does not appear to influence oxidative status in the body.
grade-c
Appetite
- Moderate See 2 studies
Mixed evidence, and even the promising evidence noted that the degree of appetite suppression was insufficient to suppress food intake.
grade-c
Blood Flow
- - See study
Insufficient evidence to support changes in blood flow.
grade-c
Blood Pressure
- Very High See all 4 studies
No significant interaction between CLA and blood pressure
grade-c
Bone Mineral Density
- - See study
No evidence to support a link between CLA and alterations in bone mineral density
grade-c
Cell Adhesion Factors (Youth)
- - See study
No significant influence on cell adhesion factors.
grade-c
DNA Damage
- Very High See 2 studies
Insufficient evidence to suggest alterations in the rate of DNA damage with CLA ingestion.
grade-c
Leptin
- Very High See 2 studies
Not enough evidence to support alterations in circulating leptin due to CLA ingestion.
grade-c
Oxidation of LDL
- - See study
No significant protective or augmenting effects on the oxidation rates of LDL-C.
grade-c
Oxygen Uptake
- - See study
grade-c
Subjective Well-Being
- - See 2 studies
Insufficient evidence to support an inherent contentment boosting effect, as the lone study was confounded with weight loss.
grade-c
Total Cholesterol
- - See study
grade-d
Asthma
- - See study
No significant interaction between CLA supplementation and asthmatic symptoms
grade-d
Cell Adhesion Factors (Elderly)
- - See study
No significant alterations in cellular adhesion factors (linked to atherosclerosis via the immune system)
grade-d
Heart Rate
- - See study
No significant interaction between heart rate and CLA supplementation
grade-d
Interleukin 2
- - See study
grade-d
Interleukin 6
- - See study
grade-d
Kidney Function
- - See study
No significant influence of CLA supplementation on renal functioning
grade-d
Symptoms of Crohn's Disease
- - See study

Studies Excluded from Consideration

Omitted due to having polar opposite effects on lipids dependent on isomer used (c9t11 v. t10c12) which doesn't fit in the Rubric which assesses CLA as a whole[1]

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Things to Note

Is a Form Of

Primary Function:

Also Known As

CLA, Rumenic Acid

Do Not Confuse With

Linoleic Acid (the basic fatty acid)

Goes Well With

  • Fucoxanthin (May increase the fat burning effects of Fucoxanthin)

  • CLA is non-stimulatory

  • CLA tends to work better in obese and sedentary individuals, but even in this population it is quite unreliable in exerting benefit

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Research Breakdown on Conjugated Linoleic Acid

1Structure and Sources

1.1Sources

1.2Structure

2Isomers of CLA

2.1c,9-t,11

2.2t,10-c,12

2.3Other Isomers

2.4Similarities

3Pharmacology

3.1Distribution

4Interactions with Lipid Metabolism

4.1Triglycerides

4.2Cholesterol

5Interactions with Glucose Metabolism

5.1Insulin Sensitivity Mechanisms

5.2Insulin Sensitivity Interventions

6Interactions with the Liver

6.1Liver Enzymes

6.2Liver Fat

7Interactions with Fat Mass

7.1Distribution

7.2Mechanisms

7.3Species Differences

7.4Metabolic Rate

7.5Intervention studies

8Interactions with Skeletal Muscle

8.1Distribution

8.2Glucose Metabolism

8.3Interventions

9Effects on Hormones

9.1Testosterone

10Interactions with Neurology

10.1Appetite

10.2Neural Progenitor Cells (NPCs)

10.3Cell Protection

10.4Interactions with the Endocannabinoid System

11Interactions with Cardiovascular Health

11.1Endothelium (Blood vessels)

11.2Blood Pressure

12Exercise and Performance

13Oxidation

13.1General Oxidation

13.2Lipid Peroxidation

14Inflammation and Immunology

14.1Mechanisms

14.2Cytokines

14.3Inflammatory Bowel Diseases

15Nutrient-Nutrient Interactions

15.1PUFAs

15.2Fucoxanthin

15.3Resveratrol

16Safety and Toxicity

16.1General

16.2During Pregnancy and Lactation
Click here to see all 167 references.

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This page is regularly updated, to include the most recently available clinical trial evidence.

Each member of our research team is required to have no conflicts of interest, including with supplement manufacturers, food companies, and industry funders. The team includes nutrition researchers, registered dietitians, physicians, and pharmacists. We have a strict editorial process.

This page features 167 references. All factual claims are followed by specifically-applicable references. Click here to see the full set of research information and references for Conjugated Linoleic Acid.

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