Gamma-linoleic acid (GLA) is an omega-6 polyunsaturated fatty acid made in the body from linolenic acid, an essential fatty acid (EFA). GLA is the product of the body’s first biochemical step in the transformation of a major essential fatty acid, linolenic acid (LA), into important prostaglandins. Prostaglandins are essential to the proper functioning of each cell. Every cell’s structure in the human body depends on fatty acids formed from GLA. Seed oils of evening primrose (Oenothera biennis L.) 10%, borage (Borago officinalis L.), 17%, and black currant (Ribes nigrum L.), 23%.
Evening primrose oil (EPO), very high in GLA, has been used for decades to treat medical conditions. Native American women chewed evening primrose seeds to relieve menstrual problems. Evening primrose was also used by Native Americans and early American settlers from Europe to treat coughs and stomach problems. In the 1800s, the leaves of the plant were used to treat several skin conditions. EPO was imported to Europe during the 1600s and 1700s, and used to treat Gout, Rheumatoid arthritis, headaches, and skin conditions. In animal studies gamma-linoleic acid has been shown to reduce certain inflammations and reduce joint tissue injury. Human studies showed similar findings in its anti-inflammatory effects. GLA has also been used as a treatment option for a number of conditions, including alcoholism, asthma, attention deficit/hyperactivity disorder (ADHD), high cholesterol, diabetic neuropathy, certain cancers, eczema (a skin inflammation), hypertension (high blood pressure), premenstrual syndrome (PMS), Rheumatoid arthritis, and Scleroderma (a skin disease.) There is also research data that indicates GLA in combination with other measures may help in treating people with Sjogren’s syndrome—a chronic inflammatory disease of the immune system that effects mostly older women.
Other animal studies suggest GLA may enhance calcium absorption, helping to reduce calcium loss and osteporosis. Osteoporosis is a disease occurring primarily in women after menopause in which the bones become very porous, break easily, and heal slowly. It may lead to curvature of the spine after vertebrae collapse. EPO supplements taken during pregnancy may reduce the need for cesarean delivery as studies suggest that EPO may facilitate vaginal delivery when used as a ‘‘cervical priming agent.’’ Among the conditions GLA is most often used for are:
- Rheumatoid arthritis.
GLA has been studied for many years for its possible effects in treating arthritis and other inflammatory conditions. GLA has been shown to be most promising in treating people with this crippling condition, due to its anti-inflammatory properties. At least three studies have shown GLA reduces inflammation and joint tissue injury, thereby reducing the pain associated with this condition. In one study, GLA reduced the incidence of tender joints by 36%, and swollen joints by 28%. ADHD. GLA are helpful (combined with other therapies) for helping to alleviate ADHD symptoms in children.
Some studies show that GLA can help improve nerve function and help reduce peripheral neuropathy, which causes numbness, tingling, pain, or burning in the feet, legs, and toes and hands, in diabetics. Recent studies have confirmed evening primrose oil as beneficial in the treatment of distal diabetic polyneuropathy, a condition involving multiple nerves.
- High cholesterol.
Research indicates that high doses of GLA may improve blood lipid levels in people with high cholesterol. Studies with laboratory animals in 1997 demonstrated the cholesterol-lowering effects of EPO. Rabbits whose diet was supplemented with 15% EPO showed a total cholesterol reduction of 25%. In a 13-week study with rats, EPO dietary supplements of 10–20%, produced lower levels of liver cholesterol than in rats on the same diet, but supplemented with palm oil, soybean oil, sunflower oil, or high-oleic safflower oil.
- Skin conditions.
Several studies showed GLA relieved symptoms such as itching, redness, and scaling of the skin, to varying degrees. It has also been shown to be helpful in reducing the symptoms of scleroderma and skin inflammations, such as dermatitis.
GLA has potential to suppress tumor growth and metastasis, the spreading of cancer from the original site to other parts of the body. In one small study, combining Vitamin C with the GLA supplement doubled the survival time for 11 patients with liver cancer. GLA has also shown promising results as a cancer therapy when combined with the anticancer drugs tamoxifen and paclitaxel. Research into its effects on cancer are in the earliest stages and GLA cannot be said to prevent or cure any type of cancer. However, it has been reported that GLA supplementation may inhibit carcinogenesis.
Several studies suggest GLAmay help reduce blood pressure in some people with hypertension and thereby decrease the risk of heart attacks. Results of these studies are not considered conclusive.
Studies show GLA is remarkably helpful in treating some PMS symptoms. One study showed that of the women who took the drug Efamol, which contains 9% GLA, 61% experienced complete relief from symptoms while 23% had partial relief. These symptoms included breast tenderness, depression, irritability, swelling, and bloating. Gamma-linolenic acid, in combination with eicosapentaenoic acid (EPA), in the form of borage seed and fish oils, significantly reduced the need for breathing support in patients with the lung condition acute respiratory distress syndrome. It cut the average number of days a patient is in a hospital’s intensive care unit from 17.5 to 12.8.
Gamma-linoleic acid is found naturally in fish, animal organs such as liver, and certain plant seed oils. The major sources of GLA are borage oil (18–27% GLA), black currant oil (15–20% GLA), and evening primrose oil (7–14% GLA). GLA is not available as a pure extract, but only as an ingredient in combination formulas. Dosage varies by condition it is used to treat:
- skin conditions: 360–750 milligrams (mg) daily
- PMS: 240–320 mg daily
- Rheumatoid arthritis: 750 mg–2.8 g daily for six to 12 months
- diabetic neuropathy: 480 mg daily
- high blood pressure: 1.3 g daily
- high cholesterol: Up to 2 g daily
The United States Food and Drug Administration (FDA) has not established recommended daily allowances (RDA) for gamma-linoleic acid. Patients should consult with a heathcare professional regarding the proper dosage. Several forms of GLA supplements are available, including a concentrated form. It is also available as evening primrose oil, borage oil, and black currant seed oil. It is also available in multi-nutrient formulas that often contain any combination of fish oil, flax seed oil, omega-6 fatty acids, and essential fatty acids. The usual amount of GLA in these is from 200–400 milligrams per capsule. The cost of a bottle of 30 capsules ranges from $8 to $15. The concentrations of GLA in these oils varies and the number of capsules needed depends on the amount of GLA.
Gamma-linoleic acid should not be used by women who are pregnant or breastfeeding without consulting a physician. Hemophiliacs and people who take the blood-thinning drug warfarin (Coumadin) should consult a physician before taking GLA. It should also not be taken before surgery because it may increase bleeding. Persons with high blood pressure or heart or blood vessel conditions should consult a physician before taking GLA.
There is no evidence that GLA is toxic in daily doses of up to 2.8 grams. There have been no reports of serious side effects by people taking GLA supplements. It is generally well tolerated by most people. Possible minor side effects include upset stomach, diarrhea, soft stool, bloating, and gas. Persons who take GLA and experience difficulty breathing, chest or throat tightness, chest pain, hives, rash, or itchy or swollen skin may be allergic to it. They should stop taking it and consult a physician immediately.
No adverse interactions between gamma-linoleic acid and other medications, vitamins, or nutritional supplements have been reported.