Overhead view of many colorful Primrose flowers (Primula acaulis)
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Evening primrose oil is harvested from the seeds of the evening primrose flower, a wildflower native to North America. Desired for its reputed health benefits, evening primrose oil has been identified as a potential treatment for several health conditions, such as eczema. Some evidence suggests that evening primrose oil might affect the levels of estrogen in your body, though the oil's effect on estrogen has not yet been definitively demonstrated.

Components of Evening Primrose Oil

Evening primrose oil contains relatively large amounts of gamma-linoleic acid, a type of omega-6 fatty acids. It's important to consume these fats through foods and dietary supplements, since your body can't produce the fatty acids on its own. Gamma-linoleic acid aids in brain functioning, supports healthy skin and hair growth, and helps regulate inflammation in your body. Evening primrose oil also might contain nutrients that interact with estrogen, although the nature of this interaction is not yet known.

Implications in Menopause

Consuming evening primrose oil might benefit women entering menopause. As a woman's ovaries shut down during the transition to menopause, she experiences a drop in estrogen levels. This estrogen decrease causes side effects such as hot flashes, which often get better after taking estrogen supplements and medications. Some women have success taking evening primrose oil, which might also help prevent side effects during the transition into menopause, according to a study published in "Menopause" in 2007. This suggests that evening primrose oil might increase estrogen levels, since it might mirror the effects of estrogen therapy for treating symptoms of menopause.

Implications in Endometriosis

Evening primrose oil also might affect endometriosis, further hinting that it might affect estrogen levels. Endometriosis occurs when uterine lining cells migrate into other tissues, then begin to menstruate, causing a painful buildup of blood. Estrogen interacts with the cells that make up the uterine lining, and estrogen levels also can affect endometriosis. Taking evening primrose oil might benefit individuals with endometriosis by helping to correct a hormone imbalance, according to the University of Maryland Medical Center, indicating that the oil might affect estrogen levels.

Considerations and Side Effects

Although the role of evening primrose oil in treating hormone-related disorders suggests it might alter the levels of estrogen in your body, as of October 2011 no study or clinical trial has carefully examined its role in regulating estrogen. As a result, it is not yet known whether evening primrose oil can cause high estrogen levels.

However, taking evening primrose oil might cause other side effects. Due to its high gamma-linoleic acid content, evening primrose oil might cause digestive upset, or increase the risk of seizures in some individuals. In addition, the supplement might interact with antipsychotic or blood-thinning medications, leading to harmful side effects. Never take evening primrose oil without consulting your physician, and seek medical attention if you notice any side effects when taking the oil.