Gamma-linolenic acid (GLA) is an essential fatty acid (EFA) in the omega-6 family that is found primarily in plant-based oils. EFAs are essential to human health but cannot be made in the body. For this reason, they must be obtained from food. EFAs are needed for normal brain function, growth and development, bone health, stimulation of skin and hair growth, regulation of metabolism, and maintenance of reproductive processes.

Linoleic acid (LA), another omega-6 fatty acid, is found in cooking oils and processed foods and converted to GLA in the body. GLA is then broken down to arachidonic acid (AA) and another substance called dihomogamma-liolenic acid (DGLA). AA can also be consumed directly from meat, and GLA is available directly from evening primrose oil (EPO), black currant seed oil, and borage oil. Most of these oils also contain some linoleic acid.

The average North American diet provides more than 10 times the necessary amount of linoleic acid and tends to have too much omega-6 fatty acids compared to omega-3 fatty acids, another important class of EFAs. In fact, for optimum health, the ratio of omega-6 to omega-3 fatty acids should be between 1:1 and 4:1. The typical North American and Israeli diets are usually in the range of 11:1 to 30:1. This imbalance contributes to the development of long-term diseases such as heart disease, cancer, asthma, arthritis, and depression as well as, possibly, increased risk of infection.

Interestingly, not all omega-6 fatty acids behave the same. Linoleic acid (not to be confused with alpha-linolenic acid, which is in the omega-3 family) and arachidonic acid (AA) tend to be unhealthy because they promote inflammation, thereby increasing the risk of the diseases mentioned when consumed in excess. In contrast, GLA may actually reduce inflammation.

Much of the GLA taken from the oils mentioned or as a supplement is not converted to AA, but rather to DGLA. DGLA competes with AA and prevents the negative inflammatory effects that AA would otherwise cause in the body. Having adequate amounts of certain nutrients in the body (including magnesium, zinc, and vitamins C, B3, and B6) helps to promote the conversion of GLA to DGLA rather than AA.

It is important to know that many experts feel that the science supporting the use of omega-3 fatty acids to reduce inflammation and prevent diseases is much stronger than the information regarding use of GLA for these purposes. Two important, and most studied, omega-3 fatty acids include eicosopentaenoic acid (EPA) and docosahexaenoic acid (DHA), both found in fish and fish oils.

Some clinicians and preliminary clinical research suggest that gamma linolenic acid (GLA) may be useful for the following purposes:

Diabetes

Omega-6 fatty acid supplementation, in the form of GLA from evening primrose oil (EPO) or other sources, may assist nerve function and help prevent nerve disease experienced by those with diabetes (called peripheral neuropathy and felt as numbness, tingling, pain, burning, or lack of sensation in the feet or legs).

Eye disease

GLA may be beneficial in dry-eye conditions such as Sjögren's syndrome (a condition with symptoms of dry eyes, dry mouth, and, often, arthritis).

Osteoporosis

A deficiency in essential fatty acids, including GLA and eicosapentaenoic acid (EPA, an omega-3 fatty acid) can lead to severe bone loss and osteoporosis. Clinical studies have reported that supplements of GLA and EPA help maintain or increase bone mass. Essential fatty acids may also enhance calcium absorption, increase calcium deposits in bones, diminish calcium loss in urine, improve bone strength, and enhance bone growth, all of which may contribute to improved bone mass and, therefore, strength.

Menopausal symptoms

Although EPO has gained some popularity for treating hot flashes, the research to date has not demonstrated a benefit of GLA or EPO over taking a placebo. However, there are individual women who report improvement so it may be worthwhile to talk to your doctor about whether it is safe for you to try EPO or another form of GLA supplements to alleviate hot flashes.

Premenstrual syndrome (PMS)

Although results of clinical studies have been mixed, some women find relief of their PMS symptoms when using GLA supplements from EPO or another source. The symptoms that seem to be helped the most are breast tenderness and feelings of depression as well as irritability and swelling and bloating from fluid retention. Breast tenderness from causes other than PMS may also improve with use of GLA.

Eczema

Several early clinical studies suggested that EPO (rich in GLA) is more beneficial than placebo at relieving symptoms, such as itching, redness, and scaling, associated with this skin condition. However, more recent clinical studies have not had the same positive results testing GLA supplements derived from EPO. The bottom line is that whether EPO and GLA supplements work for someone with eczema may be very individual. Talk to your doctor about the possibility and safety of trying GLA for this condition.

Allergies

People who are prone to allergies may require more essential fatty acids (EFAs) and often have difficulty converting LA to GLA. In fact, women and infants who are prone to allergies appear to have lower levels of GLA in breast milk and blood.

The use of EFAs to prevent allergic reactions or reduce their magnitude has had mixed results in clinical studies. There have been some reports of individuals lessening their allergic reaction by taking GLA from EPO. Well-conducted clinical studies are needed to determine whether EPO can be helpful for large numbers of people with allergies.

A clinical study evaluating the dietary intake of omega-6 fatty acids relative to the risk of having hay fever (or allergic rhinitis) found an increase risk of developing symptoms associated with hay fever (including runny nose, and itchy, watery eyes) when using omega-6 fatty acids.

Omega-6 fatty acids from the diet or supplements, such as GLA from EPO or other sources, have a longstanding history of folk use for allergies. Whether this supplement improves symptoms of the conditions listed above may be very individual. Work with your health care provider to first determine if it is safe for you to try GLA and then follow your allergy symptoms closely for any signs of improvement or lack or improvement.

Rheumatoid arthritis

Some preliminary clinicial reports suggest that GLA, from EPO, borage oil, or black currant seed oil, may diminish joint pain, swelling, and morning stiffness. GLA may also allow for reduction in the amount of pain medication used by those with rheumatoid arthritis. The studies to date, however, have been small in size. Additional clinical research would be helpful, including testing a proposed theory that using GLA and EPA (an omega-3 fatty acid from fish and fish oil) together would be helpful for rheumatoid arthritis.

Attention deficit/hyperactivity disorder (ADHD)

Research to date has suggested an improvement in symptoms and behaviors related to ADHD from omega-3 fatty acids. Results of studies supplying omega-6 fatty acids in the form of GLA from EPO or other sources to children with ADHD, however, have been mixed and, therefore, not conclusive. More research on GLA for ADHD is needed before conclusions can be drawn. In the meantime, ensuring a healthier balance of omega-3 to omega-6 fatty acids in the diet seems worthwhile for those with this behavioral condition.

Alcoholism

EPO may help lessen cravings for alcohol and prevent liver damage. Some of this information comes from animal studies. Clinical research is needed.

Cancer

Results of clinical studies looking at the relationship of omega-6 fatty acids to cancer have been mixed. While LA and AA are cancer promoting in studies of colon, breast, and other cancers, GLA has shown some benefit for breast cancer in certain studies. The information is not conclusive and is somewhat controversial. The safest bet is to eat a diet with the proper balance of omega-3 to omega-6 fatty acids (see How To Take It), starting from a young age, to try to prevent the development of cancer.

Weight loss

Results of clinical studies regarding use of EPO for weight loss have been mixed and, therefore, use of this type of supplement won't work for everyone. One study suggests that if the supplement is going to work, it does so mainly for overweight individuals for whom obesity runs in the family. In addition, a few other small studies suggest that the more overweight you are, the more likely that EPO will help. In fact, if your body weight is only 10% above normal (for example, 10 - 20 pounds above average), EPO is unlikely to help you lose weight.

High blood pressure and heart disease

Animal studies suggest that GLA -- either alone or in combination with two important omega-3 fatty acids, EPA and DHA, both found in fish and fish oil -- may lower the blood pressure in laboratory animals. Together with EPA and DHA, the GLA helped to prevent the development of heart disease in these animals as well. It is unclear whether these benefits would occur in people.

In one clinical study evaluating people with peripheral artery disease (blockage in the blood vessels in the legs from atherosclerosis or hardening of the arteries causing cramping pain when walking), men and women with this condition did experience improvement in their blood pressure from the combination of EPA and GLA. Much more clinical research is needed in people before conclusions can be drawn. Furthermore, it may not be the GLA conferring the benefit at all – the omega-3 fatty acids, which are better known for improving blood pressure and the risks for heart disease, may be solely responsible.

Ulcers

Very preliminary evidence from laboratory studies suggests that GLA from EPO may have anti-ulcer properties. It is too early to know how this might apply to people with stomach or intestinal ulcers or gastritis (inflammation of the stomach). More research is needed.

GLA is found in the plant seed oils of evening primrose, black currant, borage, and fungal oils. Spirulina (often called blue-green algae) also contains GLA.

GLA supplements are derived from evening primrose oil (EPO) as well as black currant seed and borage seed oils. The GLA supplements are often packaged in oil containing capsules. EPO has been the most researched source of GLA.

Generally, 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.

For general health, there should be a balance between omega-6 and omega-3 fatty acids. The ratio should be in the range of 2:1 - 4:1, omega-6 to omega-3. The average diet provides sufficient omega-6 fatty acids, so supplementation is usually not necessary unless treating for a specific condition, such as eczema or psoriasis, arthritis, diabetes, or breast tenderness (mastalgia).

Pediatric

For nursing infants: Adequate amounts of essential fatty acids are generally supplied in breast milk if the mother is adequately nourished.

For eczema in children 2 - 18 years of age: Evening primrose oil (EPO), 3 grams daily, divided into several smaller doses throughout the day. It is reported that the maximum dose should not be greater than 0.5 gram per kilogram of body weight daily. Consult a health care provider before using supplements in children.

Adult

For eczema or atopic dermatitis: Evening primrose oil (EPO), 4,000 - 8,000 mg daily, or gamma-linolenic acid (GLA), 2,800 mg daily, both divided into several smaller doses throughout the day.

For rheumatoid arthritis: Evening primrose oil (EPO), 3,000 mg daily, or gamma-linolenic acid (GLA), 1,400 mg daily, both divided into several smaller doses throughout the day.

For diabetes: Gamma-linolenic acid (GLA), 480 mg daily, divided into several smaller doses throughout the day.

For breast tenderness (mastalgia) or PMS: Evening primrose oil (EPO), 3,000 - 4,000 mg daily, divided into several smaller doses throughout the day.

Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable health care provider.

Omega-6 should not be used if you have a seizure disorder because there have been reports of these supplements inducing seizures. Several reports describe seizures in individuals taking evening primrose oil (EPO). Some of these seizures developed in people with a previous seizure disorder, or in individuals taking EPO in combination with anesthetics. Based on these reports, people with seizure disorders should not take EPO. Patients who plan to undergo surgery requiring anesthesia should stop taking EPO 2 weeks ahead of time because of the possibility of seizure.

Borage seed oil, and possibly other sources of gamma-linolenic acid (GLA), should not be used during pregnancy because they may be harmful to the fetus and induce early labor.

Doses of GLA greater than 3,000 mg per day should be avoided because, at that point, production of arachidonic acid (AA) increases, which may cause and increase in inflammation.

Side effects of EPO can include occasional headache, abdominal pain, nausea, and loose stools. In animal studies, gamma-linolenic acid (an ingredient of evening primrose oil) is reported to decrease blood pressure. Early results in human studies do not show consistent changes in blood pressure.

Laboratory studies found that omega-6 fatty acids, such as the fat found in corn oil, promote the growth of prostate tumor cells. Until further research is performed in this area, health care professionals recommend not using omega-6 fatty acids, including GLA, if risk or symptoms of prostate cancer exist.

If you are currently being treated with any of the following medications, you should not use omega-6 supplements without first talking to your health care provider.

Blood thinning medications -- Individuals taking blood thinning medications, including warfarin (Coumadin) or clopidogrel (Plavix) should not take omega-6 fatty acid supplements without consulting a health care provider. Omega-6 and omega-3 fatty acids may increase the risk of bleeding in sensitive individuals.

Ceftazidime -- Gamma linolenic acid (GLA) may increase the effectiveness of ceftazidime (an antibiotic in a class known as cephalosporins), against a variety of bacterial infections.

Chemotherapy for cancer -- GLA may increase the effects of anti-cancer treatments, such as doxorubicin, cisplatin, carboplatin, idarubicin, mitoxantrone, tamoxifen, vincristine, and vinblastine.

Cyclosporine -- Taking omega-6 fatty acids during therapy with cyclosporine, a medication used to suppress the immune system after an organ transplant, for example, may increase the immunosuppressive effects of this medication and may protect against kidney damage (a potential side effect from this medication).

Phenothiazines -- Individuals taking a class of medications called phenothiazines, including chlorpromazine (Thorazine), fluphenazine (Stelazine), perphenazine (Trilafon), promethazine (Compazine), and thioridazine (Mellaril), to treat schizophrenia should not take evening primrose oil (EPO) because it may interact with these medications and increase the risk of seizures. The same may be true for other omega-6 containing supplements.

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