Gamma-linolenic acid or GLA is a derivative of one of two types of essential fatty acids, linoleic acid (see below). The body uses essential fatty acids to produce three series of prostaglandins and leukotrienes, which affect inflammation and pain in either a positive or negative way. GLA supplements can tip the balance towards the series 3 prostanglandins and leukotrienes, helping to contain and cure inflammatory conditions.

Little GLA is obtained from the diet. Most is made by the body from linoleic acid. Best food sources of GLA are borage oil, black currant oil, and evening primrose oil.

GLA has been used for cyclic mastalgia or breast pains linked to the menstrual period, premenstrual syndrome, diabetic neuropathy, eczema, rheumatoid arthritis, Reynaud's phenomenon and osteoporosis, but also for allergies, asthma, bursitis, chronic fatigue syndrome, endometriosis, heart disease, irritable bowel syndrome, prostate problems, Sjoegren's disease, etc.

The GLA safety record is good, but this record refers primarily to evening primrose oil. At high dosages, a few persons reported mild headaches and gastrointestinal problems. Safe dosages for young children, pregnant and lactating women, and persons suffering from severe liver and kidney disease have not been established.