Gamma-linolenic acid (GLA) is an essential fatty acid that comes primarily from plant-based oils. Linoleic acid, which is found in cooking oils and processed foods, is converted into GLA in the body. GLA supplements are available in the form of evening primrose oil, black currant seed oil, and borage oil, which also provide linoleic acid. For example, evening primrose oil is 72 percent linoleic acid. The average North American diet provides more than 10 times the necessary amount of linoleic acid.

People who have diabetes are less able than healthy individuals to convert linoleic acid to GLA. Other conditions that appear to reduce the body's ability to convert linoleic acid to GLA include aging, alcoholism, atopic dermatitis, premenstrual syndrome, rheumatoid arthritis, cancer, and cardiovascular disease. Aging also appears to reduce conversion of linoleic acid to GLA. If you are an older person or have one of these conditions, you may want to talk to your provider about supplementing your diet with GLA.

If you have rheumatoid arthritis, you may benefit from GLA supplementation. It may enable you to take less non-steroidal anti-inflammatory drugs, which can cause stomach and intestinal problems. However, more research is needed to establish the proper dosage for long-term use.

Research has shown that GLA may help prevent cardiovascular disease by dilating blood vessels, lowering blood pressure, and preventing atherosclerosis.

Cancer is another condition where GLA may be useful. Studies in people with colon cancer, breast cancer, and melanoma show that GLA inhibits the growth of tumors and the spread of cancer.

For hemodialysis patients with uremic skin symptoms, studies show that skin conditions improved when the subjects used evening primrose oil supplements. Studies suggest that GLA is also helpful in increasing bone density and calcium absorption in people who have osteoporosis.

• Rheumatoid arthritis. GLA may reduce inflammation.
• Diabetes. GLA supplementation assists nerve function and helps prevent nerve damage caused by diabetes.
• Cancer. GLA may help suppress tumor growth and spread of cancer, particularly in breast cancer and melanoma.
• Heart disease. GLA may help prevent heart disease by inhibiting plaque formation, dilating blood vessels, and lowering blood pressure.
• Eyes. GLA is beneficial in Sjögren's syndrome and may be useful in other dry eye conditions.
• GLA supplements may help the symptoms of many conditions that occur with aging. It can also reduce the symptoms of alcoholism, atopic dermatitis, and osteoporosis.
• Menstrual problems (painful menstruation or no menstruation). Essential fatty acids such as those found in flaxseed, evening primrose, and borage oils reduce inflammation and support hormone production. Dosage is 1,000 to 1,500 mg one or two times per day.

GLA is found in the plant-seed oils of evening primrose, black currant, and borage oils. GLA is also found in human milk and, in small amounts, in a wide variety of common foods, particularly organ meats.

GLA supplements are available in several forms, including evening primrose oil, black currant seed oil, borage oil, and borage oil capsules.

Several manufacturing methods can destroy the nutrient value of GLA products. Some preferred methods use proprietary names for their process, generically known as "modified atmospheric packing methods." Generally, a high-quality oil will be certified as organic by a reputable third party, packaged in light-resistant containers, refrigerated, and marked with a freshness date.

Pediatric

For nursing infants, adequate amounts of essential fatty acids are generally supplied in breast milk. For older children, essential fatty acids should come from the diet. Because it is important to maintain a balance of fatty acids within the body, it may be appropriate to check fatty acid levels before considering supplements for children.

Adult

A recommended dosage for rheumatoid arthritis is 1,400 mg per day. As the cost of oils can be high, and lower doses are usually effective, an acceptable clinical dosage of evening primrose, black currant, or borage oil would be 1,500 mg once or twice daily.

Studies have shown that up to 2,800 mg of GLA per day is well tolerated. A healthy person eating a normal diet should consume fewer saturated fats and more polyunsaturated fats. Avoid products that contain hydrogenated fats. Discuss your total fat intake with your health care provider if you are thinking about taking GLA supplements.

GLA from dietary sources appears to be nontoxic. Talk to your health care provider about your regular diet, so he or she can help you decide if you should take GLA supplements, and what kind of supplements are best for you. Remember that GLA supplements are fats and contain a lot of calories.

GLA may increase the effectiveness of ceftazidime, an antibiotic, against a variety of bacterial infections. If you are currently taking this medication, consult your healthcare provider to determine whether this combination is appropriate for you.

GLA may also increase the effects of anti-cancer treatments, such as doxorubicin, cisplatin, carboplatin, idarubicin, mitoxantrone, tamoxifen, vincristine, and vinblastine. Your healthcare provider can tell you whether taking GLA may benefit you if you are currently undergoing chemotherapy with any of these medications.

Bolton-Smith C, Woodward M, Tavendale R. Evidence for age-related differences in the fatty acid composition of human adipose tissue, independent of diet. Eur J Clin Nutr. 1997;51:619–624.

Brzeski M, Madhok R, Capell HA. Evening primrose oil in patients with rheumatoid arthritis and side-effects of non-steroidal anti-inflammatory drugs. Br J Rheumatol. 1991;30:370–372.

Brown NA, Bron AJ, Harding JJ, Dewar HM. Nutrition supplements and the eye. Eye. 1998;12(pt 1):127–133.

Corbett R, Menez JF, Floch HH, et al. The effects of chronic ethanol administration on rat liver and erythrocyte lipid composition: modulatory role of evening primrose oil. Alcohol Alcohol. 1991;26(4):459–464.

Davies CL, Loizidou M, Cooper AJ, et al. Effect of gamma-linolenic acid on cellular uptake of structurally related anthracyclines in human drug sensitive and multidrug resistant bladder and breast cancer cell lines. Eur J Cancer. 1999;35:1534-1540.

Ensminger AH, Ensminger ME, Konlande JE, Robson JRK. Foods & Nutrition Encyclopedia. 2nd ed. Baton Rouge, Fla: CRC Press, Inc; 1994:1:684–708.

Fan YY, Chapkin RS. Importance of dietary gamma-linolenic acid in human health and nutrition. J Nutr. 1998;128:1411–1414.

Garrison RH Jr, Somer E. The Nutrition Desk Reference. 3rd ed. New Canaan, Conn: Keats Publishing, Inc; 1995:23–64.

Giamarellos-Bourboulis EJ, Grecka P, Dionyssiou-Asteriou A, et al. In vitro interactions of gamma-linolenic acid and arachidonic acid with ceftazidime on multiresistant Pseudomonas aeruginosa. Lipids. 1999;34:S151-152.

Haas EM. Staying Healthy with Nutrition. Berkley, Calif: Celestial Arts Publishing; 1992:65–79.

Holman CP, Bell AFJ. A trial of evening primrose oil in the treatment of chronic schizophrenia. J Orthomol Psychiatry. 1983;12:302–304.

Ikushima S, Fujiwara F, Todo S, Imashuku S. Gamma linolenic acid alters the cytotoxic activity of anticancer drugs on cultured human neuroblastoma cells. Anticancer Res. 1990;10:1055-1059.

Jamal GA, Carmichael H. The effects of gamma-linolenic acid on human diabetic peripheral neuropathy: a double-blind placebo-controlled trial. Diabet Med. 1990;7:319–323.

Jiang WG, Hiscox S, Bryce RP, Horrobin DF, Mansel RE. The effects of n-6 polyunsaturated fatty acids on the expression of nm-23 in human cancer cells. Br J Cancer. 1998;77:731–738.

Jiang WG, Hiscox S, Bryce RP, Horrobin DF, Mansel RE. Gamma linolenic acid regulates expression of maspin and the motility of cancer cells. Biochem Biophys Res Commun. 1997;237:639–644.

Kenny FS, Pinder SE, Ellis IO et al. Gamma linolenic acid with tamoxifen as primary therapy tn breast cancer. Int J Cancer. 2000;85:643-648.

Kruger MC, Coetzer H, deWinter R, Gericke G, Papendorp DH. Calcium, gamma-linolenic acid and eicosapentaenoic acid supplementation in senile osteoporosis. Aging (Milano). 1998;10:385–394.

Leventhal LJ, Boyce EG, Zurier Rb. Treatment of rheumatoid arthritis with blackcurrant seed oil. Br J Rheumatol. 1994;33:847–852.

Madhavi N, Das UN. Effect of n-6 and n-3 fatty acids on the survival of vincristine sensitive and resistant human cervical carcinoma cells in vitro. Cancer Lett. 1994;84:31-41.

Miller LG. Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions. Arch Intern Med. 1998;158(20):2200–2211.

Murray MT. Encyclopedia of Nutritional Supplements. Rocklin, Calif: Prima Publishing; 1996:239–278.

Newstrom H. Nutrients Catalog. Jefferson, NC: McFarland & Co., Inc; 1993:103–105.

Papanikolaou N, Darlametsos I, Tsipas G, et al. Effects of OKY-046 andnifedipine in cyclosporine-induced renal dysfunction in rats. Prostaglandins Leukot Essent Fatty Acids. 1996;55(4):249–256.

Plumb JA, Luo W, Kerr DJ. Effect of polyunsaturated fatty acids on the drug sensitivity of human tumour cell lines resistant to either cisplatin or doxorubicin. Br J Cancer. 1993;67:728-733.

Puolakka J, Makarainen L, Viinikka L, Ylikorkala O. Biochemical and clinical effects of treating the premenstrual syndrome with prostaglandin synthesis precursors. J Reprod Med. 1985;30:149–153.

Shils ME, Olson JA, Shike M, Ross AC. Modern Nutrition in Health and Disease. 9th ed. Baltimore, Md: Williams & Wilkins; 1999:90–92; 1377–1378.

Wagner W, Nootbaar-Wagner U. Prophylactic treatment of migraine with gamma-linolenic and alpha-linolenic acids. Cephalalgia. 1997;17:127–130.

Werbach MR. Nutritional Influences on Illness. 2nd ed. Tarzana, Calif: Third Line Press; 1993:13–22; 655–671.

Zurier RB, Rossetti RG, Jacobson EW, et al. Gamma-Linolenic acid treatment of rheumatoid arthritis. A randomized, placebo-controlled trial. Arthritis Rheum. 1996;39:1808–1817.