Starflower oil, also known as borage seed oil, is a good source of gamma-linolenic acid, or GLA. In fact, it has even more than the popular evening primrose oil. This omega-6 fatty acid, along with omega-3 fatty acids, plays an important role in brain function, normal growth and development, skin and hair growth, bone health and metabolism regulation, according to the University of Maryland Medical Center. Starflower oil can have side effects, however.
You may suffer gastrointestinal side effects with starflower oil, according to George T. Grossberg and Barry Fox, authors of "The Essential Herb-Drug-Vitamin Interaction Guide." These include belching, bloating and diarrhea.
You increase your risk of bleeding or bruising if you take starflower oil with blood-thinning medications such as aspirin, warfarin or clopidogrel. If you take blood thinners, UMMC advises you to consult a healthcare provider before taking any type of omega-6 fatty acid. You also increase risk for bleeding when you use starflower along with herbs that affect blood platelets, including ginger, garlic, ginkgo biloba, turmeric and white willow. If you have a bleeding disorder, starflower oil may worsen it, advise Grossberg and Fox.
The GLA in starflower oil can increase the effects of the antibiotic ceftazidime, anti-cancer treatments, and the immunosuppressive medication cyclosporine given after organ transplant, according to UMMC. It also can raise risk of seizures when taken along with phenothiazines, used to treat schizophrenia.
Starflower may worsen existing liver disease, according to Grossberg and Fox. That's because it has small amounts of amabiline, an alkaloid that can injure the liver, according to the Memorial Sloan-Kettering Cancer Center in New York. Consuming 1 or 2g starflower oil each day can also mean you're taking in up to 10ug toxic unsaturated pyrrolizidine alkaloids, or UPAs. You can, however, seek starflower oil products that are certified free of UPAs. This means they have 0.5 to 1ug per gram. Germany's Federal Health Agency recommends people should take in no more than 1ug of UPAs per day.