The leaves and bark are sedative and astringent, and were used in Native American medicine for stomach, liver and female complaints. Folk medicine used the plant to treat hangovers. European settlers in the New World, named it “King’s Cure-All,” and used it to treat skin diseases.
One of the active ingredients in evening primrose oil is gamma-linolenic acid (GLA), and Evening Primrose is one of the few plants to contain this important fatty acid. Borage also contains gamma-linolenic acid. GLA functions by helping production of prostaglandins (PFE1). Prostaglandins help reduce inflammation. Prostaglandins are important for many other body functions as well, including the clotting of blood, and cholesterol production. The body can manufacture gamma-linolenic acid if it has adequate supply of one of the essential fatty acids: linolenic acid. But this mechanism is frequently stalled as a result of dietary deficiencies, insufficient enzymes and too much intake of processed, saturated fat. The oil contains about 280 mg. of GLA in 2,600 mg. of the oil, which is considered the basic therapeutic dose.
Many health conditions are known to benefit from gamma-linolenic acid, including allergies, multiple sclerosis, fibrocystic breast disease, arthritis, and even depression.
Evening Primrose oil has also shown effectiveness in treating alcoholism and for weight control. The oil reduces withdrawal symptoms from alcohol as well as depression. In weight control, the oil stimulates brown fat tissue to burn more calories.
A study conducted at the Samsung Medical Center School of Medicine in Korea showed evening primrose oil to be highly effective in treating eczema. Dermatitis patients suffering from dry, itchy, and scaly skin displayed less pruritus and lesions when supplemented with evening primrose oil. The study determined that evening primrose oil is effective in treating non-inflammatory dermatitis, acne, psoriasis, as well as eczema.
Evening primrose oil has been shown to reduce high serum cholesterol and to lower blood pressure. The mechanism is via the gamma-linolenic acid’s ability to inhibit blood clots and reduce risk of spasms in the arteries, both of which contribute to heart attacks or strokes. Lowered levels of PGE1 lead to elevated cholesterol levels, and even changes in the blood sugar levels that cause diabetes-like symptoms.
Hyperactivity in Children
A study with evening primrose oil in children showed its effectiveness in treating hyperactivity. Two-thirds of the children in the study showed improvement in their school behavior after supplementation with evening primrose oil. The supplementation was given orally and on the skin, and some of the best results were found when the oil was rubbed onto the childrens’ skin. Researchers surmise that this method of administering the oil was more effective because it overrode any issues of indigestion or malnutrition.
Another interesting function of GLA is in its ability to aid immune response. GLA and other essential fatty acids are part of the chain of nutrients that create interferons. Interferons (IFNs) are proteins that are created by the cells to fight viruses.
Fertility and PMS
Evening primrose oil has a marked effect on the female hormonal system. Low levels of GLA have been shown to trigger symptoms of PMS, and the oil has been touted as a fertility aid, because it encourages the production of cervical mucus, which can assist fertilization. It has also been prescribed to lower the risk of preeclampsia and eclampsia in pregnancy.
Mild side effects of evening primrose oil consumption can include nausea, diarrhea, and headaches. People taking blood-thinning drugs should avoid evening primrose oil, as well as those who are pregnant or who are taking drugs for epilepsy or schizophrenia, because of possible drug interactions.