What is GLA (Gamma-Linolenic Acid)?
Gamma-Linolenic Acid, or GLA, is a specific omega-6 polyunsaturated fatty acid (PUFA). Unlike many other omega-6s, which can be pro-inflammatory, GLA is known for its anti-inflammatory effects. The body can naturally produce GLA from linoleic acid (LA), a common omega-6 found in cooking oils and meat. However, this conversion process can be impaired by factors like aging, diabetes, or poor nutrition, leading some to seek supplemental sources.
Sources of GLA
GLA is predominantly found in the seed oils of specific plants, including:
- Borage oil (starflower oil), which is the richest source of GLA.
- Evening primrose oil (EPO).
- Black currant seed oil.
How GLA Works in the Body
Once consumed, GLA is converted by the body into dihomo-gamma-linolenic acid (DGLA). DGLA can then be further metabolized to produce anti-inflammatory eicosanoids, such as prostaglandin E1 (PGE1). This metabolic pathway is what gives GLA its potent anti-inflammatory properties, which are distinct from the metabolic actions of CLA.
What is CLA (Conjugated Linoleic Acid)?
Conjugated Linoleic Acid, or CLA, is not a single fatty acid but a family of at least 28 different isomers of linoleic acid. The most common isomers found in supplements are cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12). CLA is naturally produced in the digestive system of ruminant animals (like cattle, goats, and sheep) and enters the human diet primarily through their meat and dairy products. The CLA used in supplements is often synthetically produced from plant oils, like safflower oil, resulting in a different isomer ratio than found naturally.
Sources of CLA
Major dietary sources include:
- Ruminant Meats: Beef and lamb, particularly from grass-fed animals, have the highest natural concentrations of CLA.
- Dairy Products: Milk, cheese, and butter from ruminants contain CLA.
- Supplements: Most commercial CLA supplements are made from safflower oil via a chemical alteration process.
How CLA Works in the Body
CLA, particularly the t10,c12 isomer, has been studied for its potential effects on body composition, including reducing body fat and increasing lean muscle mass, primarily in animal models. The mechanisms include reducing fat cell differentiation and increasing fat burning. However, human studies show more modest and often inconsistent results, especially regarding weight loss. High doses of supplemental CLA, particularly the t10,c12 isomer, have been associated with adverse metabolic effects, such as increased insulin resistance in some individuals.
GLA vs. CLA: A Head-to-Head Comparison
To highlight the fundamental differences, here is a comparison of GLA and CLA:
- Chemical Identity: GLA is a single, specific omega-6 fatty acid, whereas CLA is a mixture of various isomers of linoleic acid.
- Source: GLA comes from specific plant seed oils (borage, evening primrose), while natural CLA is from ruminant animal products (meat and dairy), and supplemental CLA is often from safflower oil.
- Primary Metabolic Role: GLA primarily functions as a precursor to anti-inflammatory compounds. CLA is known for its potential effects on body composition, though its action is complex and isomer-dependent.
- Research Focus: Research on GLA has historically focused on inflammatory conditions, while CLA research has heavily centered on weight management and body composition.
| Feature | GLA (Gamma-Linolenic Acid) | CLA (Conjugated Linoleic Acid) |
|---|---|---|
| Chemical Structure | A specific omega-6 fatty acid | A family of isomers of linoleic acid |
| Primary Sources | Borage oil, evening primrose oil, black currant oil | Ruminant meat and dairy; supplements from safflower oil |
| Key Metabolic Product | Converted to anti-inflammatory PGE1 | Contains isomers with varied effects, including potential fat-regulating properties |
| Main Health Focus | Inflammation, skin conditions, arthritis | Body composition (fat reduction), though effects are modest in humans |
| Potential Side Effects | Generally well-tolerated at standard doses | High supplemental doses may lead to adverse metabolic effects like insulin resistance |
Distinct Health Benefits: GLA's Focus on Inflammation vs. CLA's on Body Composition
GLA and CLA are investigated for distinct health applications, reflecting their different metabolic functions. The evidence for their efficacy also varies significantly.
GLA's Anti-Inflammatory Actions
The primary health benefits associated with GLA stem from its conversion into anti-inflammatory eicosanoids. Research has explored its use for:
- Diabetic Neuropathy: Some studies show GLA may help alleviate nerve damage symptoms in people with diabetes, especially when blood sugar is well-controlled.
- Rheumatoid Arthritis (RA): GLA may help reduce inflammation and joint pain associated with RA, often used as a complementary therapy.
- Skin Health: Due to its role in regulating inflammation and supporting the skin barrier, GLA is often used for inflammatory skin conditions like eczema.
CLA's Potential for Body Composition
In contrast, CLA's most publicized benefit is its potential effect on body fat and lean mass, though the scientific results are mixed and often less dramatic in humans than in animal studies.
- Body Fat Reduction: While many animal studies show significant fat reduction with CLA, human trials typically show only modest effects, with fat loss often described as small or unreliable.
- Improved Body Composition: Some research suggests CLA can increase lean body mass, particularly in combination with exercise, but the results are inconsistent.
- Adverse Effects: High supplemental doses of CLA, particularly the t10,c12 isomer, have been linked to potential adverse metabolic outcomes, such as increased insulin resistance and fat accumulation in the liver.
Is One Better Than the Other?
Determining whether GLA or CLA is 'better' is dependent on your specific health goals, as they are not interchangeable. If you are seeking potential anti-inflammatory benefits, GLA is the more appropriate fatty acid to consider, derived from sources like evening primrose or borage oil. If your focus is on body composition, CLA is the subject of more research, though the evidence for dramatic fat loss in humans is limited and inconsistent. For those interested in CLA, it is essential to be aware of the varied effects of its isomers and the potential adverse outcomes associated with high supplemental doses. Before taking any supplement, consulting a healthcare professional is crucial to determine if it is appropriate for you. Further information on CLA's effects can be found in a detailed review from Virginia Tech, which addresses its health implications and effects on body composition Virginia Tech.
Conclusion
In summary, while their acronyms are similar, GLA (Gamma-Linolenic Acid) and CLA (Conjugated Linoleic Acid) are entirely different fatty acids with distinct chemical structures, sources, and biological activities. GLA is a specific omega-6 known for its anti-inflammatory properties, primarily sourced from plant oils. CLA is a mixture of isomers, naturally found in ruminant meat and dairy, and often studied for its more complex and inconsistent effects on body composition. Misunderstanding the difference could lead to incorrect supplementation for your health objectives. Always remember that for reliable, impactful results, a balanced diet and consistent exercise are foundational to improving body composition and overall health.
