Understanding the Two Types of Linolenic Acid
When people refer to linolenic acid, they are most often talking about alpha-linolenic acid (ALA), an omega-3 fatty acid. However, there is also gamma-linolenic acid (GLA), an omega-6 fatty acid. It is important to distinguish between these two, as they come from different sources and have different metabolic pathways, though both are polyunsaturated fats with important bodily functions. The body can convert ALA into the longer-chain omega-3s, EPA and DHA, although this process is inefficient. Meanwhile, GLA is produced in the body from linoleic acid (LA), another essential omega-6 fatty acid, and is also found in specific plant oils.
Top Food Sources of Alpha-Linolenic Acid (ALA)
For those seeking to increase their ALA intake through diet, focusing on certain plant-based foods is the most effective strategy. These sources are often high in fiber, vitamins, and minerals, providing additional health benefits beyond their essential fatty acid content.
- Flaxseed and Flaxseed Oil: These are perhaps the most renowned and richest sources of ALA. A single tablespoon of flaxseed oil can contain over 7 grams of ALA. Ground flaxseed, which is more easily digested than whole seeds, is also an excellent source and can be added to cereals, smoothies, and baked goods.
- Chia Seeds: Another superfood rich in ALA, chia seeds are a versatile option for boosting your intake. One ounce (28g) of chia seeds provides over 5 grams of ALA.
- Walnuts: These nuts are a good source of ALA, with a one-ounce serving providing a significant amount of the daily recommended intake. Walnuts are easy to snack on or add to salads and oatmeal.
- Vegetable Oils: Several cooking oils are high in ALA. Canola oil and soybean oil are common choices for cooking and salad dressings that offer a decent amount of this omega-3 fat.
- Green Leafy Vegetables: While their overall fat content is low, vegetables like kale, spinach, and Brussels sprouts contain ALA. Because their total lipid content is low, they do not contribute as significantly as seeds or oils, but they add to overall intake.
Food and Supplement Sources of Gamma-Linolenic Acid (GLA)
GLA is not as widely available in common food sources as ALA but can be obtained from specific seed oils and, to a lesser extent, from animal products.
- Borage Oil (Starflower Oil): This is the richest supplemental source of GLA, containing between 17% and 25% GLA.
- Evening Primrose Oil (EPO): This is a well-known source of GLA, commonly used in supplements, which contains 7% to 10% GLA.
- Black Currant Seed Oil: Providing a mid-range concentration of GLA, this oil is another supplemental option for increasing intake.
- Hemp Seed Oil: This oil contains both GLA and ALA, offering a blend of omega-3 and omega-6 fatty acids.
- Animal Products: While the body can synthesize GLA from dietary linoleic acid, some animal products, such as organ meats and egg yolks, contain small amounts of GLA and its derivatives.
Comparison of Linolenic Acid Sources
| Source Category | Common Examples | Primary Type | Average ALA Content | Notes |
|---|---|---|---|---|
| Seeds/Nuts | Flaxseeds, Chia Seeds, Walnuts | ALA | High (Flaxseed oil: ~7.26g/tbsp) | Also excellent sources of fiber and minerals. |
| Vegetable Oils | Flaxseed Oil, Canola Oil, Soybean Oil | ALA | Medium (Canola oil: ~1.28g/tbsp) | Used for cooking, dressings, and spreads. |
| Supplemental Oils | Borage Oil, Evening Primrose Oil | GLA | N/A | High-concentration, non-food sources for targeted supplementation. |
| Leafy Greens | Kale, Spinach, Brussels Sprouts | ALA | Low (Kale: ~0.18g/cup raw) | Contribute to total intake but are not the primary source. |
| Animal Products | Organ meats, Eggs | GLA | Low | Minor source for GLA; omega-3 content depends on diet. |
Is it Better to Get Linolenic Acid from Food or Supplements?
For ALA, getting it from whole food sources like flaxseeds, chia seeds, and walnuts is generally recommended. These foods offer a complete nutritional package, including fiber, protein, and other micronutrients that contribute to overall health. Furthermore, they help maintain a healthier balance of omega-3 and omega-6 fatty acids in the diet.
For GLA, which is not abundant in a wide range of common foods, supplementation is often the most practical way to achieve a significant intake. Supplements like borage oil or evening primrose oil provide a concentrated dose of GLA. This is particularly relevant for those with conditions that affect the body's ability to convert linoleic acid into GLA, or for therapeutic uses under medical guidance.
It is crucial to remember that while ALA is beneficial, the conversion to EPA and DHA is limited. Therefore, consuming marine sources like fatty fish or algae-based supplements is necessary for adequate levels of EPA and DHA, especially for individuals not consuming fish.
Conclusion
Linolenic acid, in its alpha-linolenic acid (ALA) and gamma-linolenic acid (GLA) forms, is accessible through both diet and supplements. For ALA, the best strategy is to rely on nutrient-dense plant foods like flaxseeds, chia seeds, and walnuts, and to use ALA-rich vegetable oils. These whole-food options provide a broad spectrum of nutritional benefits. For GLA, which is less common in everyday foods, supplements like borage or evening primrose oil offer a concentrated and reliable source. By understanding the distinct sources of each type, you can make informed dietary choices to ensure a sufficient intake of these essential fatty acids.
What is the difference between alpha-linolenic acid (ALA) and gamma-linolenic acid (GLA)?
ALA is an omega-3 fatty acid found primarily in plant sources like flaxseed and walnuts, while GLA is an omega-6 fatty acid found in specific oils like borage and evening primrose. They belong to different families of essential fatty acids.
What are the richest food sources of alpha-linolenic acid (ALA)?
The richest food sources of ALA are flaxseed oil, flaxseeds, chia seeds, and walnuts. These foods can be easily incorporated into a daily diet through various meals and snacks.
Can ALA supplements be used instead of food sources?
Yes, ALA supplements, typically in the form of flaxseed oil, can be used. However, whole food sources are often preferred as they provide additional nutrients like fiber and protein, offering a more complete nutritional profile.
Are there any vegan-friendly sources of linolenic acid?
Yes, all the primary food sources of ALA—such as flaxseeds, chia seeds, walnuts, canola oil, and soybean oil—are vegan. Supplemental GLA from borage or evening primrose oil is also plant-based.
What are the best supplemental sources of gamma-linolenic acid (GLA)?
The most concentrated supplemental sources of GLA are borage oil, evening primrose oil, and black currant seed oil, which are widely available in softgel form.
Does heating affect linolenic acid in oils?
Polyunsaturated fatty acids like linolenic acid are sensitive to heat and can degrade. To preserve the fatty acid content, it is best to use ALA-rich oils like flaxseed oil in uncooked applications like salad dressings or smoothies.
How can I increase my linolenic acid intake without supplements?
To boost your ALA intake, add ground flaxseed to your morning cereal, snack on walnuts, and use canola or soybean oil for cooking. To get GLA, you would need to use specific oils in supplements.
