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Gamma-Linolenic Acid, or GLA, is an omega-6 polyunsaturated fatty acid with 18 carbons and three double bonds. GLA is found in a variety of plant oils; it is also produced in the body from the essential fatty acid, linoleic acid (LA). The body converts linoleic acid to GLA and then to arachidonic acid (AA). GLA is conditionally essential in the event that there is decreased activity of delta-6-desaturase which is the enzyme that is necessary for converting LA into GLA. GLA has anti-inflammatory and antithrombotic action and may also provide lipid-lowering activity. GLA is the precursor for EPA which exerts antithrombotic, anti-inflammatory, and anti-atherogenic activity which may account for the action of GLA..
GLA is primarily found in plant based oils such as:
The following are the primary uses for Gamma-Linolenic Acid: 
- Inflammatory Conditions: Studies using GLA for inflammatory conditions such as rheumatoid arthritis have been going on for many years. This application is due to its ability to modulate the inflammatory pathways towards anti-inflammation. It has been shown to decrease inflammation and reduce joint tissue injury in animal models. Several other clinical studies on humans have also shown promising effects. There is also some preliminary research available to suggest that GLA may be beneficial in the treatment of Sjogren's syndrome, and Ulcerative Colitis.
- Skin Conditions: The treatment of atopic eczema using GLA has shown mixed results in the literature with regards to its efficacy.
- Osteoporosis: GLA may also enhance calcium absorption, reduce calcium excretion, and increase calcium deposition in the bone and has therefore been researched for its use in treating osteoporosis. In one pilot study, women treated with GLA and calcium carbonate had increased lumbar and femoral bone mineral density over 36 months.
- Improving Blood Lipid Profile: Higher doses have shown some beneficial effects in lowering cholesterol and triglycerides.
- Cancer: The research into the area of using GLA for cancer treatment in humans is just beginning. There has been some promising evidence to suggest some benefit in using GLA in the treatment of cerebral gliomas. Other studies suggest that there may be some benefit in the treatment of pancreatic cancer.
- Diabetic Neuropathy: There appears to be a certain subgroup of people with diabetic neuropathy that benefit from GLA supplementation.
- Premenstrual Syndrome: The positive evidence appears to be lacking for the benefit of using GLA for the treatment of PMS.
- Menopausal Hot Flashes: The positive evidence appears to be lacking for the benefit of using GLA for the treatment of menopausal hot flashes.
The following are sources of Gamma-Linolenic Acid 
- borage seed oil (with a GLA concentration of 20-27%)
- black current oil (with a GLA concentration of 15-20%)
- evening primrose seed oil (with a GLA concentration of 7-14%)
- GLA is available in capsule form.
- Adult: typical dose ranges from 360mg - 2.8g
Gamma-linolenic acid (GLA) is generally tolerated well without side effects. Specific safety precautions include:
- Pregnancy and Breastfeeding
- GLA should not be used in this population unless under medical supervision.
- Those on warfarin and hemophiliacs should use GLA with caution due to its antithrombotic action. GLA should not be used before surgery (discontinue 2 weeks prior).
- Drug and Herbal Interactions:
- Aspirin, NSAIDs, Allium sativa (garlic), and Gingko biloba - Rare occurrences of increased nosebleeds and/or increased susceptibility to bruising may occur with concomitant use of GLA with anyone of these drugs or herbs. Lower dose of or discontinue use of GLA if these occur.
- Hendler Sheldon S, Rorvik David (Editors) (2011) PDR for Nutritional Supplements, Medical Economics Company Inc.