In the Middle Ages, people used borage to treat heart disease and rheumatism and to reduce inflammation. Now it is making a comeback for some of the same medicinal uses: borage oil is one of the three major supplemental sources of gamma-linolenic acid (GLA), a polyunsaturated fat that is used to treat a number of conditions, including rheumatoid arthritis, eczema, and premenstrual syndrome (PMS). Besides borage oil, GLA comes from the seeds of the evening primrose plant and from black currants. The human body also manufactures its own supply of GLA from linoleic acid, which is abundant in vegetable oils and meats. In the body, linoleic acid is converted first to GLA and then to dihomo-gamma-linolenic acid (DGLA). DGLA is essential for the production of prostaglandin E1, an important hormone-like chemical that reduces inflammation, boosts immunity, lowers blood pressure, keeps platelets from sticking together, and improves blood vessel tone.

As we age, our bodies can become less efficient at converting linoleic acid to GLA and therefore less efficient at producing the beneficial prostaglandins. Several diseases, including cancer, eczema, multiple sclerosis and diabetes, also make the conversion less efficient.

This doesn’t necessarily mean that supplementing with GLA will cure or prevent these diseases. In fact, some experts warn that GLA supplements have the potential to aggravate symptoms because GLA and DGLA can actually help promote inflammation.