Is CLA Heart Healthy? A Critical Look at the Evidence

November 17, 2025 •

3 min read

Research regarding conjugated linoleic acid (CLA) and cardiovascular health is inconsistent, presenting both potential benefits and notable risks. This complex fatty acid, naturally found in dairy and meat, has been studied for its effects on cholesterol, blood pressure, and inflammation, raising the critical question: Is CLA heart healthy and what does the current evidence suggest?

Quick Summary

The evidence on CLA's effects on heart health is conflicting, with some studies suggesting potential benefits for heart failure risk and others showing risks like lowered HDL cholesterol and increased inflammatory markers, especially from high-dose supplements.

Key Points

Conflicting Evidence: Research on CLA's impact on heart health shows inconsistent results; some studies suggest benefits while others indicate potential risks.
Natural vs. Supplemental: The CLA found in grass-fed dairy and meat is the c9,t11 isomer, which differs from the high-dose, 50:50 isomer mix found in most supplements made from vegetable oils.
HDL Cholesterol Risk: Several human studies and meta-analyses suggest that CLA supplementation can adversely affect the lipid profile by lowering beneficial HDL cholesterol.
Inflammation Markers: High-dose CLA supplements have been associated with increased levels of C-reactive protein (CRP), a marker for inflammation and cardiovascular disease risk.
Heart Failure Association: One large observational study linked higher dietary CLA intake (from dairy fat) to a lower risk of heart failure, though not specifically coronary heart disease.
Metabolic Side Effects: Supplementation, especially at higher doses, may increase insulin resistance and cause fat accumulation in the liver.

Understanding CLA and its Origins

Conjugated linoleic acid (CLA) is a group of polyunsaturated omega-6 fatty acid isomers. The most common are cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12). It is a natural trans fat, distinct from industrial trans fats.

CLA is naturally present in meat and dairy from ruminant animals, with higher levels in grass-fed animals. CLA supplements are made by chemically altering vegetable oils, resulting in a different isomer blend and much higher doses than food sources.

The Mixed Evidence on CLA and Heart Health

The scientific literature on CLA and heart health is contradictory. While some animal studies showed promise, human trials haven't consistently demonstrated cardiovascular risk factor protection.

Potential Benefits and Positive Findings

Heart Failure Risk: An observational study linked higher CLA levels in older men's serum (from dairy fat) to a reduced heart failure risk. This needs further confirmation.
Atherosclerosis: Animal studies suggested benefits, but human trials have not consistently replicated these findings. One study suggested that tissue levels of c9,t11 CLA might correlate with a lower heart attack risk.
Blood Pressure: Some research indicates CLA with ramipril may improve blood pressure reduction, but CLA alone doesn't show this effect.
Anti-inflammatory Effects: The c9,t11 isomer is potentially anti-inflammatory. Some studies show reduced inflammatory markers in specific groups, but results are inconsistent.

Potential Risks and Negative Findings

Cholesterol Profile: Many human studies report CLA supplementation can lower HDL ("good") cholesterol. Other studies show no effect or even increased total cholesterol, likely due to isomer blend and dosage.
Inflammation Markers: Some studies, particularly with the t10,c12 isomer, show CLA supplements increase C-reactive protein (CRP), an inflammatory marker linked to heart disease.
Insulin Resistance: High-dose CLA supplements are linked to increased insulin resistance, a heart disease risk factor, especially in those with metabolic syndrome.
Liver Fat Accumulation: High doses in some studies led to increased liver fat, a step toward metabolic syndrome and diabetes.

Natural Sources vs. Supplements

CLA from food and supplements have different implications for heart health. Food CLA is mainly the c9,t11 isomer. Supplements use a 50:50 mix of c9,t11 and t10,c12 from vegetable oils. Higher doses and the altered isomer balance in supplements may explain the negative effects seen in some studies.

Comparison: CLA from Food vs. Supplements


Feature	CLA from Natural Food Sources	CLA from Supplements
Source	Ruminant meat, dairy (especially from grass-fed animals)	Vegetable oils (e.g., safflower oil), chemically altered
Dose	Low, in natural dietary amounts	High, often 3-6+ grams per day
Primary Isomer	Primarily cis-9, trans-11	Balanced 50:50 blend of cis-9, trans-11 and trans-10, cis-12
Cardiovascular Effects	Potential benefits observed in some observational studies, especially for heart failure	Mixed results; associated with risks like lowered HDL and increased CRP
Other Nutrients	Consumed alongside other beneficial nutrients like Vitamin K2	Isolated compound, without accompanying nutrients
Adverse Effects	Not typically associated with negative effects in normal dietary amounts	Linked to potential side effects including digestive issues and insulin resistance

A Note on Conflicting Research

Variability in study results is due to factors including dosage, isomer ratio, study duration, participant health status, and the source of CLA.

Conclusion: So, Is CLA Heart Healthy?

The question of whether is CLA heart healthy has no straightforward answer. While natural dietary CLA is weakly linked to some benefits like reduced heart failure risk, high-dose supplements from vegetable oils pose risks. Concerns include negative impacts on cholesterol (lowering HDL), increased inflammatory markers (CRP), and potential insulin resistance. Given the conflicting evidence and potential risks of supplements, consuming natural dietary sources as part of a balanced diet seems a safer approach for heart health. Consult a healthcare provider before taking CLA supplements, as more research is needed.

For more information on a human study about serum CLA and heart failure risk, you can review the abstract from the Journal of the American Heart Association(https://www.ahajournals.org/doi/abs/10.1161/jaha.117.006653).

Frequently Asked Questions

Yes, CLA from natural sources like grass-fed dairy and meat is generally considered safer than supplements. The dosage is lower and the isomer composition is different, lacking the higher concentration of the t10,c12 isomer that has been linked to adverse effects.

The evidence on CLA and cholesterol is mixed. While some studies show no significant effect, meta-analyses have found that supplementation may actually decrease your beneficial HDL cholesterol, which is a significant health concern.

Potential heart-related side effects from CLA supplements include decreased HDL cholesterol, increased inflammatory markers like C-reactive protein (CRP), and increased insulin resistance, especially in individuals with metabolic syndrome.

Some research suggests that taking CLA alongside blood pressure medication may enhance its effects. However, taking CLA on its own has not been shown to consistently lower blood pressure.

Unlike omega-3 fatty acids (found in fish oil), which have strong and consistent evidence supporting their cardioprotective effects, the research on CLA's benefits for heart health is controversial and conflicting, with potential risks identified.

Individuals with metabolic syndrome, diabetes, or pre-existing heart conditions should exercise caution. Those with high blood pressure who are taking medication should also consult a doctor, as CLA might cause blood pressure to drop too low.

The inconsistencies in CLA research are likely due to variations in study design, such as differences in dosage, the specific CLA isomers used, the duration of the study, and the health status of participants.