Note: This monograph discusses omega-6 fatty acids in general and is based on the literature search term omega-6 fatty acids. The effects of omega-6 fatty acids within the body as well as supplemental omega-6 fatty acids are included in the monograph. The essential fatty acid linoleic acid (18:2n-6) is not discussed in detail in this monograph. Oils rich in omega-6 fatty acids (e.g., corn oil) are not specifically discussed in this monograph. Oils rich in gamma-linolenic acid (18:3n-6), such as evening primrose oil, are not specifically discussed in this monograph.
Omega-6 fatty acids are a family of polyunsaturated fatty acids including linoleic acid, gamma-linolenic acid, and arachidonic acid. In North America, omega-6 fatty acids are found in adequate amounts in the diet, as they are found in salad dressings, margarines, and other plant and animal oil sources. The negative reputation of omega-6 fatty acids is likely based on inadequate intakes of omega-3 fatty acids and not excessive omega-6 fatty acid intakes.
Although not commonly used alone as dietary supplements, there is some evidence in support of omega-6 fatty acids, in combination with omega-3 fatty acids, for attention-deficit hyperactivity disorder (ADHD) and coordination disorders, as well as eye disorders. Also, levels of certain omega-6 fatty acids in the blood were found to be lower in multiple sclerosis patients vs. healthy controls with similar dietary intakes. However, there is a lack of evidence in support of supplementation in multiple sclerosis patients.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Both omega-3 (mainly docosahexaenoic acid) and omega-6 (mainly gamma-linolenic acid) fatty acids have been studied in patients with ADHD. Further research is needed before conclusions may be drawn.
Both omega-3 (mainly docosahexaenoic acid) and omega-6 (mainly gamma-linolenic acid) fatty acids have been studied in patients with developmental disorders and ADHD. Further research is needed.
Limited research suggests that a supplement containing omega-6 fatty acids may improve the symptoms of meibomian gland dysfunction. However, it is not clear if the supplement also contained other agents. Additional research on the use of omega-6 fatty acids alone is needed before conclusions may be drawn.
Limited research suggests that a supplement containing omega-6 fatty acids may improve the results of photorefractive keratectomy (a type of laser eye surgery). However, it is not clear if the supplement also contained other agents. Additional research on the use of omega-6 fatty acids alone is needed before conclusions may be drawn.
Lower levels of certain omega-6 fatty acids were detected in the plasma of multiple sclerosis patients than in healthy controls. Additional research is required before conclusions may be drawn.
* Key to grades
A: Strong scientific evidence for this use B: Good scientific evidence for this use C: Unclear scientific evidence for this use D: Fair scientific evidence for this use (it may not work) F: Strong scientific evidence against this use (it likley does not work)
Tradition / Theory
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.
Arthritis, atopic dermatitis, cancer, cystic fibrosis, depression, diabetes, heart disease, high cholesterol, HIV/AIDS, immune system regulation, inflammation, liver damage (from impaired bile flow), mastalgia (breast pain), neurological disorders.
For eye disorders (meibomian gland dysfunction), 28.5 milligrams of linoleic acid and 15 milligrams of gamma-linolenic acid have been taken by mouth daily for 180 days in MedilarT tablets (a combination product), which also contain omega-3 fatty acids, vitamin E, vitamin C, vitamin B6, vitamin B12, and zinc.
For multiple sclerosis, 11-23 grams of linoleic acid has been taken by mouth daily. Information on the duration of treatment was lacking.
Children (under 18 years old)
There is no proven safe or effective dose of omega-6 fatty acids in children.
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Avoid with known allergy or hypersensitivity to potential vegetable oil sources of omega-6 fatty acids, such as corn oil, sunflower oil, and soybean oil.
It is commonly thought that the increase in omega-6 fatty acids in the diet in North America plays a role in the increased prevalence of allergies.
Side Effects and Warnings
Omega-6 fatty acids are considered to be safe and healthy fatty acids and are commonly found in the diet. However, many health experts believe that, based on the high omega-6 fatty acid intakes in North America, it may be important to increase omega-3 fatty acids in the diet, thus reducing the omega-6:omega-3 fatty acid intake ratio.
Omega-6 fatty acids may have procancer effects or harmful effects on the heart. They may also be associated with Crohn's disease, excessive fat tissue development, attention-deficit hyperactivity disorder (ADHD), depression, neuroticism, altered depression scale scores, development of parenteral nutrition-associated liver disease in children with short bowel syndrome, an elevated risk of fracture in the elderly, Reye's syndrome, exercise-induced asthma, or a high rejection rate in kidney transplants.
Omega-6 fatty acids may increase the risk of bleeding. Caution is advised in patients with bleeding disorders or those taking drugs, herbs, or supplements that may increase the risk of bleeding. Dosing adjustments may be necessary.
Omega-6 fatty acids may cause insulin resistance and affect blood sugar levels. Caution is advised in patients with diabetes or low blood sugar and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
Omega-6 fatty acids may cause high blood pressure. Caution is advised in patients taking drugs, herbs, or supplements that lower blood pressure.
Caution is advised when used in combination with anti-inflammatory agents, as omega-6 fatty acids are considered proinflammatory as a group.
Caution is advised when used in patients with heart disease, those prone to cancer or taking anticancer agents, those prone to bone fracture or taking medications for osteoporosis, those with psychiatric disorders or taking psychiatric medications, and those using cholesterol-lowering agents.
Avoid supplementation with arachidonic acid, based on theoretical increases in inflammation and disorders caused by inflammatory processes, including heart disease.
Avoid with known allergy or hypersensitivity to potential vegetable oil sources of omega-6 fatty acids, such as corn oil, sunflower oil, and soybean oil. It is commonly thought that the increase in omega-6 fatty acids in the diet in North America plays a role in the increased prevalence of allergies.
Pregnancy and Breastfeeding
There is a lack of high-quality scientific evidence on the use of omega-6 supplements in pregnant or breastfeeding women. In early research, compared with women giving birth to full-term infants, arachidonic acid and all omega-6 fatty acids were higher in women giving birth to preterm infants.
Omega-6 fatty acids may cause insulin resistance and affect blood sugar levels. Caution is advised when using medications that may also affect blood sugar. Patients taking insulin or drugs for diabetes by mouth should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
Omega-6 fatty acids may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin®) or heparin, antiplatelet drugs such as clopidogrel (Plavix®), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
Omega-6 fatty acids may cause high blood pressure. Caution is advised in patients taking drugs that lower blood pressure.
Omega-6 fatty acids may also interact with agents that affect the immune system, agents used for the heart, antiasthmatics, anticancer agents, anti-inflammatory agents, cholesterol-lowering agents, clofibric acid, drugs used for osteoporosis, estrogen and progestin combinations, gentamicin, iron, neurologic agents, norepinephrine, psychiatric agents, or thyroid hormones.
Interactions with Herbs and Dietary Supplements
Omega-6 fatty acids may cause insulin resistance and affect blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.
Omega-6 fatty acids may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
Omega-6 fatty acids may cause high blood pressure. Caution is advised in patients taking herbs or supplements that lower blood pressure.
Omega-6 fatty acids may also interact with alpha-linolenic acid supplements, alpha-linolenic acid-containing foods, antiasthmatics, anticancer agents, anti-inflammatories, beef fat, beta-carotene, cholesterol-lowering agents, docosahexaenoic acid, fish, flaxseed, flaxseed oil, formula diets, herbs and supplements used for the heart, herbs and supplements that affect the immune system, iron, a Mediterranean diet, neurological agents, omega-3 fatty acids, osteoporosis herbs and supplements, psychiatric agents, quercetin, saturated fat, tetradecylthioacetic acid, trans fat, vitamin A, vitamin E, or a Western-type diet.
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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.