Unlike saturated fats, polyunsaturated fatty acids are healthy and an important part of your diet. Linoleic acid and linolenic acid are examples of unsaturated fats that are essential for good health.
Linoleic Acid vs. Linolenic Acid
Linolenic acid and linoleic acid are similarly named omega fatty acids that have different roles in human health and nutrition, per Oregon State University.
Linolenic acid most commonly refers to alpha-linolenic acid (ALA), an omega-3 fatty acid found in many nuts, vegetables and oils.
Linoleic acid is the most common type of omega-6 fatty acid, an essential polyunsaturated fatty acid. Some linoleic acid foods include certain nuts, seeds and refined vegetable oils. Omega-6 fatty acids are an important part of a healthy diet and are particularly beneficial for your immune system and metabolism.
Conjugated linoleic acid (CLA) is the conjugated form of linoleic acid that's more commonly found in animal-based foods like meat and milk products. CLA can appear in different levels in specific animal products, according to May 2006 research in Meat Science. Factors that influence CLA content include whether the animal has multiple stomachs and what kind of foods it's eaten.
Linoleic acid and conjugated linoleic acid are similar, but they behave differently in the body due to their different origins and small structural differences. Linoleic acid is much easier to get than CLA from foods.
There are also two types of fatty acids that have linolenic acid in their names: gamma-linolenic acid (GLA) and dihomo-gamma-linolenic acid (DGLA). They're found in nut, seed and vegetable oils, per an August 2016 European Journal of Pharmacology study.
What Is Alpha-Linolenic Acid?
Alpha-linolenic acid, or ALA, is a type of omega-3 fatty acid that is derived from plants. It is found in high amounts in flaxseeds and flaxseed oil and in lesser amounts in canola, soy and walnut oils; as well as in soybeans, tofu and pumpkin seeds. It can also be taken as a supplement in liquid or capsule form.
ALA is the most common type of omega-3 fatty acid and the most important from a dietary perspective. ALA acts as a precursor to other omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), according to August 2014 research in Food and Chemical Toxicology. Only small amounts of ALA are converted into DHA and EPA.
ALA is tied to many benefits, including anti-cancer, anti-inflammatory, anti-osteoporotic, anti-oxidant, cardioprotective and neuroprotective effects, according to August 2014 research in Food & Chemical Toxicology.
Heart-Healthy Benefits of ALA
Eating foods high in ALA is associated with lower rates of death from coronary heart disease and from heart attack, according to a December 2015 Circulation study.
Sources of Alpha-Linolenic Acid
Many foods are rich in ALA. You can find this essential fatty acid in many plant-based foods, including, according to the USDA:
- Oils: flaxseed oil and soybean oil
- Nuts: walnuts and pistachios
- Seeds: flax, chia seeds and hempseed
The Dietary Guidelines for Americans recommend a total of 1.1 to 1.6 grams of ALA per day for a healthy diet. A 2019 study in the Proceedings of Nutrition Society Journal suggests this value may be increased to at least 2 grams per day.
When you eat foods with ALA, the body processes it into EPA and DHA.
Why Omega-3s Are Important
Only recently has ALA been considered medically relevant. For instance, a 2015 study in the BioMed Research International Journal shows how ALA can increase levels of brain-derived neurotrophic factor (BDNF), a neuroprotective protein. BDNF has been shown to act as an antidepressant and to improve outcomes following stroke.
The Health Benefits of Omega-6s
Linoleic acid and other omega-6 fatty acids are essential for good health. Linoleic acid acts as a precursor, converting into other long-chain polyunsaturated fatty acids, including arachidonic acid and DGLA.
Omega-6 fatty acids are associated with improved health, with fatty acids like linoleic acid, arachidonic acid and DGLA linked to the prevention of heart disease, per November 2015 research in the Cochrane Database of Systematic Reviews. Replacing saturated fat with linoleic acid reduces total and LDL cholesterol and it might be linked to improved insulin sensitivity and blood pressure, per Harvard Health Publishing.
CLA, which is found in animal products like milk and meat, is tied to anticarcinogenic, antiobesity, antidiabetic and antihypertensive properties, found a November 2014 study in Obesity Research & Clinical Practice.
While linoleic acid has its health benefits, eating too much is linked with health risks, per the 2014 study in Biochimie. Too much linoleic acid means that there will be too much arachidonic acid and other fatty acids converted, resulting in the overactivity of certain bodily systems.
For example, omega-6 fatty acids are associated with immune system function, which, in excess, can increase inflammation, per a September 2016 study in Prostaglandins & Other Lipid Mediators. Eating too many omega-6 fatty acids has also been linked to obesity.
Healthy Omega-3 and Omega-6 Ratios
Omega-3 and omega-6 fatty acids are both essential fats that have a lot of overlap in terms of nutritional importance, but our bodies require them in different quantities for good health.
People living in western societies, such as the United States and the United Kingdom, eat many foods rich in omega-6 fatty acids — so many, in fact, that these regions are thought to eat too many omega-6 fatty acids compared to omega-3 fatty acids, according to January 2014 research in Biochimie. Ideally, the ratio should be fairly small, but this can be hard if you eat a typical Western diet.
Lowering your ratio of omega-6 to omega-3s might even help with health issues, according to early October 2006 research in Biomedicine and Pharmacotherapy. Omega-6 to omega-3 in the range of 3:1 or 2:1 has been shown to help reduce inflammation in people with inflammatory diseases, while a ratio of 5-to-1 is helpful for those with asthma. In contrast, most Western diets have a ratio of 15:1 to 16.7:1, and ratios as low as 10:1 can have negative effects on your health.
It’s important to look at foods like oils, which most people use on a daily basis. Oils such as flaxseed and soybean can have high amounts of omega-6s, while those like walnut are much richer in omega-3s.
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- Journal of Nutrition and Metabolism: "Health Implications of High Dietary Omega-6 Polyunsaturated Fatty Acids"
- Biomedicine and Pharmacotherapy: "Polyunsaturated Fatty Acids in Biology and Diseases: The Importance of the Ratio of Omega-6/Omega-3 Essential Fatty Acids"
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- Oregon State University: "Essential Fatty Acids"