What are Linoleic Acid and CLA?
Linoleic acid is a polyunsaturated omega-6 fatty acid found in plant foods like seeds, nuts, and vegetable oils. The human body cannot produce linoleic acid, so it must be obtained through diet. In contrast, conjugated linoleic acid (CLA) refers to a family of isomers of linoleic acid, with a slightly different molecular structure. While some CLA is naturally produced in the gut and found in dairy and meat from ruminant animals, most CLA supplements are synthesized from linoleic acid in vegetable oils. This distinction is crucial because the effects of naturally occurring CLA from food and the synthetic isomers in supplements can differ.
Potential Benefits of Linoleic Acid (CLA) Supplements
Weight Management and Body Composition
One of the most widely researched benefits of CLA supplements is their potential role in weight management and improving body composition. The theory is that CLA can influence fat metabolism, promoting fat breakdown and reducing fat storage.
- Reduction of Body Fat: Some animal studies and a handful of human trials have shown that CLA supplementation can lead to a modest reduction in body fat mass. The effects appear to be most noticeable during the first several months of use.
- Increased Lean Muscle Mass: Certain studies suggest CLA may help increase lean body mass, particularly in conjunction with exercise. However, the evidence is mixed, with other studies showing no significant effect.
Heart Health and Lipid Profiles
Linoleic acid itself has a well-established role in promoting cardiovascular health, particularly when used to replace saturated fats in the diet. For CLA supplements, the data is less clear.
- Improved Cholesterol: Some research indicates that dietary linoleic acid can lower LDL ("bad") cholesterol levels. For CLA supplements, results are inconsistent, with some studies showing a reduction in LDL but also a potentially harmful reduction in HDL ("good") cholesterol.
- Lowered Inflammation Markers: Higher levels of linoleic acid in the blood are associated with lower cardiometabolic risk and reduced inflammation markers. However, some studies on CLA supplements have shown mixed or even adverse effects on inflammation.
Supporting Skin Health
As an essential component of skin, linoleic acid is crucial for maintaining the skin's barrier function and hydration.
- Moisture Retention: Linoleic acid plays a direct role in the skin's water permeability barrier, helping to retain moisture and prevent dryness.
- Acne and Anti-inflammatory Effects: It can help regulate sebum production and has anti-inflammatory properties, making it beneficial for acne-prone or reactive skin when applied topically. Supplemental CLA's effect on skin health is less studied and may not mirror the benefits of direct topical application.
Comparison: Dietary Linoleic Acid vs. Supplemental CLA
To clarify the difference between obtaining linoleic acid from food and taking a CLA supplement, consider the following comparison table:
| Feature | Dietary Linoleic Acid (LA) | Supplemental Conjugated Linoleic Acid (CLA) |
|---|---|---|
| Source | Naturally occurring in vegetable oils (safflower, sunflower, corn), nuts, and seeds. Small amounts of natural CLA are in grass-fed dairy and meat. | Synthesized from linoleic acid (e.g., safflower oil), creating a mixture of CLA isomers. |
| Isomers | Primarily the natural cis-9, cis-12 form. | Contains a mixture of isomers, including the prominent cis-9, trans-11 and trans-10, cis-12 forms. |
| Dosage | Varies widely based on diet. Average intakes in Western diets can range from 12-17g/day. | Typically dosed at 3-6 grams per day in studies. |
| Health Effects | Linked to reduced cardiometabolic risk, lower LDL cholesterol, and essential skin function. | Mixed results, especially for weight loss and some metabolic indicators; potential negative effects on HDL cholesterol at high doses. |
| Safety Profile | Considered safe when consumed as part of a balanced diet. | Mild side effects are common. Higher, long-term doses raise concerns about insulin resistance and liver fat accumulation. |
Risks, Considerations, and Side Effects
While supplements are generally regarded as safe at recommended dosages, particularly those derived from CLA, there are significant considerations and potential side effects to be aware of.
- Digestive Issues: Mild gastrointestinal problems such as nausea, diarrhea, and upset stomach are frequently reported side effects.
- Metabolic Concerns: High doses of CLA supplements have been associated with adverse metabolic effects in some human and animal studies, including increased liver fat, impaired insulin sensitivity, and potentially worsening metabolic syndrome or diabetes.
- Altered Cholesterol Profile: Some research indicates that certain CLA isomers found in supplements can increase triglycerides and LDL cholesterol while decreasing beneficial HDL cholesterol. This is different from the cholesterol-lowering effects associated with dietary linoleic acid.
- Bleeding Risk: Due to its potential effect on blood clotting, CLA supplementation might increase the risk of bruising and bleeding, especially for individuals on anticoagulant medications.
Conclusion
Linoleic acid is an essential omega-6 fatty acid with well-documented benefits for cardiovascular and skin health when consumed through a balanced diet. However, for linoleic acid supplements, typically containing conjugated linoleic acid (CLA), the evidence is less conclusive and often inconsistent, particularly regarding weight loss and body composition. While some studies show modest positive effects, others report minimal or conflicting results, and concerns exist about potential side effects at higher doses, including negative impacts on insulin sensitivity and cholesterol levels. For most people, obtaining linoleic acid from natural food sources is the safest and most effective approach. Those considering supplementation should weigh the potential for modest benefits against the possible risks and consult a healthcare professional.
For more detailed information on polyunsaturated fatty acids and cardiometabolic health, refer to the review published in Lipids in Health and Disease.
Frequently Asked Questions
Is linoleic acid different from conjugated linoleic acid (CLA)?
Yes, linoleic acid is the primary omega-6 fatty acid found in plant foods, while CLA is a family of isomers derived from linoleic acid, with a different molecular structure, often produced synthetically for supplements.
Do linoleic acid supplements cause weight loss?
Some studies on CLA supplements show a modest reduction in body fat, but results are often inconsistent and the effects are typically small, especially when compared to effects observed in animal studies.
What are the main side effects of CLA supplements?
Common side effects include digestive issues like nausea and diarrhea. At higher doses, there are concerns about increased liver fat, insulin resistance, and potential negative changes to cholesterol levels.
How can I get enough linoleic acid from my diet?
Good food sources of linoleic acid include vegetable oils (safflower, sunflower, soybean), nuts, and seeds. A balanced diet typically provides sufficient amounts.
Should people with diabetes avoid linoleic acid supplements?
Given some studies indicating that CLA supplements can potentially worsen insulin resistance and raise blood sugar levels, individuals with diabetes or metabolic syndrome should be cautious and consult their doctor.
Can CLA supplements interact with medications?
Yes, CLA supplements might interfere with blood clotting and could increase the risk of bruising and bleeding for individuals taking blood-thinning medications.
Are the health benefits of linoleic acid and CLA the same?
No, the health effects are different. Dietary linoleic acid, particularly when replacing saturated fats, has a more consistent and robust evidence base for cardiovascular benefits. The effects of supplemental CLA are less consistent and carry some metabolic risks not associated with dietary linoleic acid.
