GLA, or gamma linolenic acid, is one of the omega-6 fatty acids and is found in plant-based oils such as the seeds of evening primrose and black currant. GLA also is found in egg yolks. According to the American Cancer Society, some studies show that GLA is effective in slowing or stopping the growth of some types of cancer cells. These studies were performed in a laboratory using tissue samples. Thus far, there is very little evidence that GLA supplements work to prevent or treat cancer in humans, but research is ongoing.
Inflammation may occur if GLA supplements are taken in excess; avoid doses greater than 3,000 mg per day, according to the University of Maryland Medical Center (UMMC). Normally, inflammation occurs if the body is fighting off an infection or foreign substance such as a bacteria or virus. However, if inflammation occurs without a cause, the body’s normally protective immune system could damage its own tissues. Before taking this supplement, consult with a health care provider.
Increased Bleeding Time
If high doses of GLA are taken for long periods, increased bleeding time may occur. According to a study performed on rats and published in October 2009 in the "Pakistan Journal of Pharmaceutical Sciences," increased levels of GLA found in primrose oil result in excess levels of arachiodonic acid in the body. This is a component that makes blood thinner. Thin blood may result in bruising and more time for blood to coagulate if cut or scraped. Coagulation allows blood to clot then heal at a site of injury. It is advised to report any of these conditions to your health care provider.
History of Seizures
People who have a history of seizures or even a family history of seizures should not take this supplement. GLA can exacerbate seizures in this population. Specifically, the UMMC notes that there are several reports of seizures occurring in those taking evening primrose oil. Seizures are also a side effect in people without a seizure disorder but who are taking evening primrose oil in combination with anesthetics. Those who plan to have surgery that requires anesthesia should stop taking evening primrose oil two weeks prior to surgery.