Evidence Level
Moderate
Evening primrose oil has been studied extensively for mastalgia and PMS since the 1980s. The Cardiff Mastalgia Clinic pioneered its clinical use, finding that 3g daily provided meaningful relief in cyclical breast pain. Pruthi et al. (2010) conducted a more recent placebo-controlled trial and confirmed EPO's efficacy for mastalgia. For PMS, the evidence is more equivocal — Budeiri et al. (1996) performed a meta-analysis of 7 controlled trials and found that while individual studies showed benefit, the overall evidence was limited by small sample sizes and methodological issues. The GLA mechanism is well-established biochemically: GLA → DGLA → PGE1, shifting the prostaglandin balance away from pro-inflammatory pathways.