Omega-6 Fatty Acids

Overview

Omega-6 is an essential fatty acid, and the first fat in the omega-6 family of fatty acids. Omega-6 gets enzymatically converted into longer chain fatty acids of the omega-6 family, which are gamma-linolenic acid or GLA, dihomogamma-linolenic acid or DGLA, and arachidonic acid or AA. In addition to the quantity of fatty acids that are consumed, the ratio of omega-6 to omega-3 fatty acids is important. Some scientists feel the ideal ratio should be similar to that which occurs in mother’s milk, which is approximately 5:1. However, studies reveal that many Americans consume far too much omega-6, with an omega-6 to omega-3 ratio of about 30:1. This condition exists because of the high consumption of refined polyunsaturated vegetable oils such as corn, safflower, and sunflower oils, which contain from 60-80 percent omega-6, but zero omega-3. For this reason, most Americans do not need to consume extra omega-6. However, it seems that many people do not have good enzymatic conversion of omega-6 to gamma-linolenic acid (GLA), and thus oils supplying GLA can be beneficial for a variety of health conditions.

Dosage Info

Dosage Range

50-300mg daily of gamma linolenic acid (GLA).

Most Common Dosage

120mg daily of gamma linolenic acid (GLA).

Dosage Forms

Liquid, capsules, and tablets.

Adult RDI

None established

Adult ODA

None established

RDA

  • : None established

Interactions and Depletions

Interactions

Active Forms

Linoleic acid (omega-6 or LA) and gamma linolenic acid (GLA).

Absorption

Omega-6 fatty acids are acted on by bile from the gallbladder. Bile contains lecithin, which emulsifies fats into small droplets. This increases the surface area so that enzymes secreted from the pancreas can digest fats in the duodenum. Digestion and absorption of fats, including omega-6 fatty acids, takes place in the small intestines.

Toxicities & Precautions

General

There is no known toxicity associated with omega-6 fatty acids.

Functions in the Body

Fatty Acid Synthesis

Linoleic acid (LA) is the precursor to the longer chain omega-6 fatty acids such as gamma-linolenic acid (GLA), and arachidonic acid (AA).

Anti-inflammatory

The longer chain omega-6 fatty acid called arachidonic acid is the precursor to the series 2 prostaglandins (PGE2), which are pro-inflammatory and can cause an increase in swelling, pain sensitivity, blood viscosity.

Cellular Structure

Linoleic acid is one of the structural components in cell walls and cellular membranes throughout the body.

Prostaglandin Formation

Linoleic acid and gamma-linolenic acid are the precursors for the synthesis of an important group of chemicals called the series 1 prostaglandins (PGE1), which are anti-inflammatory, cause vasodilation, decrease platelet aggregation and enhance immune function.

Clinical Applications

Periodontal Disease

Borage oil supplementation, a source of omega-6 PUFA, gamma-linolenic acid (GLA), may have beneficial effects on periodontal inflammation. A study found that patients treated with borage oil experienced decreased symptoms of periodontitis. (1)

Diabetes

People with diabetes have a dysfunction in the enzymatic conversion of omega-6 or linoleic acid to GLA, which may play a role in the development of diabetic neuropathy. (2) In a double-blind, placebo-controlled trial, patients receiving GLA experienced significant improvements in a variety of nerve function parameters. (3)

Rheumatoid Arthritis

RA patients were given 1.4 gm/day of GLA from borage oil for 24 weeks. In a double-blind, placebo-controlled trial. Improvements were reported in physicians' and patients' global assessment of disease activity; joint tenderness, joint swelling, morning stiffness, grip strength, and ability to do daily activities. Tender joint score decreased by 45 percent and swollen joint score decreased by 41 percent. (4)

Painful Breasts

Painful breasts affects 70 percent of women at some time in their lives and records at a breast clinic indicate that about 50 percent of their referrals are due to this condition. Gamma-linolenic acid supplementation has been used as the first line of therapy, providing results equal to drug therapy with danazol and bromocriptine, but with far fewer side effects. (5) In a study with 291 women suffering from painful breasts, 45 percent of those with symptoms related to their menstrual cycle improved with GLA supplementation from evening primrose oil and 27 percent of women with symptoms not associated with their menstrual cycles gained significant improvement. (6)

Immune Dysfunction

Research suggests that the prostaglandins known as PGE1, which are made from DGLA are important regulators of the immune system. It is suggested that viral infections (7) and various nutritional deficiencies (8) may inhibit the synthesis of PGE1 from DGLA and thus weaken the immune system with regard to AIDS as well as other chronic diseases. In these cases, supplementation with GLA and/or DGLA would be beneficial.

Alcoholism

Alcohol appears to inhibit the conversion of omega-6 to GLA and GLA supplementation may actually help to overcome the addiction to alcohol. (9) In an animal study, supplementation with GLA in the form of evening primrose oil significantly reduced the withdrawal symptoms from alcohol addiction. (10)

Eczema

It has been reported that patients with eczema have elevated linoleic acid, but low levels of gamma-linolenic acid, indicating an inability to convert LA to GLA, which inhibits prostaglandin synthesis. (11) A meta-analysis reviewed 9 placebo-controlled trials with GLA supplementation from evening primrose oil. Both patient and doctor’s ratings reported improvement over beginning scores. (12) However, some trials with evening primrose oil have not shown improvement.

PMS

It has been reported that women with PMS have a defect in their ability to convert linoleic acid into gamma-linolenic acid (GLA). (13) Double-blind, palcebo-controlled trials have demonstrated that providing GLA in the form of evening primrose oil is a highly effective treatment for the depression and irritability, the breast pain and tenderness, and the fluid retention associated with premenstrual syndrome. (14)

Symptoms and Causes of Deficiency

People are seldom deficient in linoleic acid (omega-6). Instead most people consume far too much linoleic acid. However, it appears that some people, especially patients with diabetes, do not effectively convert linoleic acid into the longer chain omega-6 fatty acids. These individuals are found to be deficient in gamma-linolenic acid (GLA) and dihomogamma-linolenic acid (DGLA), which are the precursors of the series 1 prostaglandins (PGE1). Inhibition of PGE1 synthesis results in increase inflammation, cardiovascular problems such as increased vasoconstriction and platelet aggregation, and suppression of the immune system.

Dietary Sources

Linoleic acid (omega-6 or LA) is contained in the following oils: evening primrose oil (72%), black currant seed oil (44%), flaxseed oil (18%). Corn, sunflower, and safflower oils contain over 60 percent omega-6. Gamma linolenic acid (GLA) is contained in the following oils: evening primrose oil (9%), black current seed oil (18%), borage oil (26%). Beef and other animal meats, milk and eggs are major dietary sources of arachidonic acid. Americans’ high consumption of these foods helps explain why the tissues and cellular membranes of many Americans reportedly have excessively high levels of arachidonic acid.

References

  1. View Abstract: Rosenstein ED, Kushner LJ, Kramer N, Kazandjian G. Pilot study of dietary fatty acid supplementation in the treatment of adult periodontitis. Prostaglandins Leukot Essent Fatty Acids. Mar2003;68(3):213-8.
  2. View Abstract: Horrobin DF. Essential Fatty Acids in the Management of Impaired Nerve Function in Diabetes. Diabetes. Sep1997;46(Suppl 2):S90-93.
  3. View Abstract: Jamal GA, et al. The Effect of Gamma-linolenic Acid on Human Diabetic Peripheral Neuropathy: A Double-blind Placebo-controlled Trial. Diabet Med. May1990;7(4):319-23.
  4. View Abstract: Leventhal LJ, et al. Treatment of Rheumatoid Arthritis with Gammalinolenic Acid. Ann Intern Med. Nov1993;119(9):867-73.
  5. View Abstract: Holland PA, et al. Drug Therapy of Mastalgia. What are the Options? Drugs. Nov1994;48(5):709-16.
  6. View Abstract: Pye JK, et al. Clinical Experience of Drug Treatments for Mastalgia. Lancet. Aug1985;2(8451):373-77.
  7. View Abstract: Marcus SG. Breakdown of P.G.E. 1 Synthesis is Responsible for the Acquired Immunodeficiency Syndrome. Med Hypotheses. Sep1984;15(1):39-46.
  8. View Abstract: Das UN. Nutrients, Essential Fatty Acids and Prostaglandins Interact to Augment Immune Responses and Prevent Genetic Damage and Cancer. Nutrition. Apr1989;5(2):106-10.
  9. View Abstract: Horrobin DF. Essential Fatty Acids, Prostaglandins, and Alcoholism: An Overview. Alcohol Clin Exp Res. Feb1987;11(1):2-9.
  10. Segarnick DJ. Biochemical and Behavioral Interactions Between Prostaglandin E1 and Alcohol. Clinical Uses of Essential Fatty Acids. New York: Eden Press; 1982:199-204.
  11. View Abstract: Horrobin DF. Fatty Acid Metabolism in Health and Disease: The Role of Delta-6-desaturase. Am J Clin Nutr. May1993;57(5 Suppl):732S-736S.
  12. View Abstract: Morse PF, et al. Meta-analysis of Placebo-controlled Studies of the Efficacy of Epogam in the Treatment of Atopic Eczema. Relationship Between Plasma Essential Fatty Acid Changes and Clinical Response. Br J Dermatol. Jul1989;121(1):75-90.
  13. View Abstract: Brush MG, et al. Abnormal Essential Fatty Acid Levels in Plasma of Women with Premenstrual Syndrome. Am J Obstet Gynecol. Oct1984;150(4):363-66.
  14. Horrobin DF, et al. Abnormalities in Plasma Essential Fatty Acid Levels in Women with Pre-menstrual Syndrome and with Non-malignant Breast Disease. J Nutr Med. 1991;2:259-64.