Understanding Gamma Linoleic Acid (GLA)
Gamma linoleic acid (GLA) is an omega-6 polyunsaturated fatty acid that plays a vital role in the body, primarily as a precursor to important hormone-like substances called prostaglandins. Unlike the abundant omega-6 fatty acid, linoleic acid (LA), which is found in many common vegetable oils, GLA is found in only a few concentrated sources. The body can convert LA into GLA, but this process can be inefficient due to factors like aging, poor nutrition, and certain health conditions. This is why direct intake of GLA from specific dietary sources is important for some individuals. The eicosanoids produced from GLA are known for their anti-inflammatory properties, distinguishing them from the pro-inflammatory eicosanoids produced from arachidonic acid, another omega-6 fatty acid.
The Richest Plant-Based Sources of GLA
The most potent sources of GLA are special plant seed oils, which are typically consumed as dietary supplements rather than cooking oils due to their high concentration.
Borage Oil (Starflower Oil)
Borage oil, also known as starflower oil, is the richest known natural source of GLA. Extracted from the seeds of the Borago officinalis plant, its GLA content can range from 18% to 26%. This high concentration makes it a preferred source for those seeking a therapeutic dose of GLA. Borage oil is typically available in capsule form and has been studied for its potential benefits related to inflammatory conditions, although results are mixed.
Black Currant Seed Oil
Black currant seed oil is another significant source of GLA, containing approximately 15% to 20%. Notably, it also contains alpha-linolenic acid (ALA), an omega-3 fatty acid, offering a blend of both essential fatty acids. Like borage oil, it is commonly found in supplement form and has been investigated for its use in immune function and inflammatory support.
Evening Primrose Oil
Evening primrose oil (EPO) is perhaps the most well-known source of GLA, though its concentration is lower than borage and black currant oils, typically around 7% to 10%. Derived from the seeds of the evening primrose plant (Oenothera biennis), it is widely marketed for women's health concerns, such as PMS and menopause symptoms. While some studies show promising results, evidence for its effectiveness on conditions like eczema is weak.
Hemp Seed Oil
Hemp seed oil contains a more moderate amount of GLA, usually around 3%. Its primary benefit comes from its well-balanced ratio of omega-6 to omega-3 fatty acids, which some consider optimal for human health. Hemp seed oil can be used as a finishing oil for cold dishes like salads, as its low smoke point makes it unsuitable for cooking. It is often sold as a food product rather than strictly as a supplement.
Comparison of GLA-Rich Plant Oils
| Feature | Borage Oil (Starflower Oil) | Black Currant Seed Oil | Evening Primrose Oil | Hemp Seed Oil |
|---|---|---|---|---|
| GLA Concentration | ~18-26% | ~15-20% | ~7-10% | ~3% |
| Omega-3 Content | Low | Significant (ALA) | Low | Significant (ALA) |
| Processing | Cold-pressed | Cold-pressed | Cold-pressed | Cold-pressed |
| Primary Use | High-dose supplements | Balanced supplement | Women's health supplements | Culinary and supplements |
| Considerations | Contains PAs (look for 'PA-free') | Also provides omega-3s | Most widely studied for women's health | Contains a balanced fatty acid profile |
Other Natural Food Sources
Outside of these concentrated seed oils, obtaining significant GLA from common foods is challenging. While the body typically relies on converting linoleic acid, some minor sources exist:
- Human Milk: Contains a natural, small amount of GLA, which provides essential fatty acids to infants.
- Organ Meats: Certain organ meats contain trace amounts of GLA.
- Spirulina: Some microalgal species, including spirulina, also contain GLA.
Incorporating GLA into Your Diet
For those aiming to increase their GLA intake, consuming the concentrated seed oils is the most effective method, bypassing the potentially inefficient metabolic conversion process.
- Dietary Supplements: The most common and reliable way to consume GLA is through softgel capsules of borage, evening primrose, or black currant oil. Look for cold-pressed products to ensure maximum potency. Always consult a healthcare provider before beginning any new supplement regimen.
- Topical Application: Borage and evening primrose oils are also used topically for skin conditions, leveraging their anti-inflammatory properties. However, topical application may not be effective for systemic conditions.
- Culinary Use: Hemp seed oil can be drizzled over salads, pastas, or roasted vegetables after cooking to preserve its delicate fatty acids. It should not be used for high-heat cooking.
Conclusion
While the body can produce some of its own gamma linoleic acid, dedicated dietary sources are rare outside of specific plant seed oils. For those seeking to boost their intake of this anti-inflammatory omega-6 fatty acid, borage oil, black currant seed oil, and evening primrose oil are the most potent options, with borage being the richest. Incorporating these foods into your regimen, either through supplements or in the case of hemp oil, culinary use, can help support the body's production of beneficial prostaglandins. As always, consulting a healthcare professional is recommended to determine the best approach for your individual health needs. For more details on the metabolism and effects of GLA, see the resource on ScienceDirect.
A Quick Guide to GLA Sources
- Borage Oil: The single richest source, often found in high-dose supplements.
- Black Currant Seed Oil: Contains a high amount of GLA plus beneficial omega-3s.
- Evening Primrose Oil: A traditional source of GLA, popular for women's health.
- Hemp Seed Oil: Provides a balanced ratio of essential fatty acids, including some GLA.
- Supplements over Food: Due to low concentrations in common foods, supplements are the most effective method for high GLA intake.
- Inefficient Conversion: Many factors can impair the body's ability to convert linoleic acid into GLA, making direct dietary sources valuable.
