Evening Primrose Oil for Menstrual Cramps

I was told that evening primrose oil would alleviate some pain from menstrual cramps. I have been searching for information on this. Can you please give me some info on this?

Evening primrose oil is often recommended for pre-menstrual syndrome. For example, Judy Graham's book, "Evening Primrose Oil" (available from Richters), has a chapter on how this herb can help women suffering from PMS. For menstrual cramps, evening primrose is less known as an aid, but here is what Christopher Hobbs and Kathi Keville say about it in their book, "Women's Herbs, Women's Health (also available from Richters):
"Evening primrose, borage, and black currant seed oils all contain gamma-linoleic acid, or GLA, a ntural medicine that is sometimes effective for cramps. It takes several months of supplementation to be effective. We also find that this oil doesn't work for every woman, and studies to determine its effectiveness have been inconclusive."
They go on to recommend other herbs and formulas for menstrual cramp. Some of the herbs they recommend include cramp bark, motherwort, chamomile, wild yam, and others. They give recipes for a cramp-relieving tea and a menstrual cramp oil, as well as others for heavy periods, blood building, and what they call "Easy Flow Formula" for regular and painless menstrual periods.