Evening Primrose Oil and Fish Oil for Severe Chronic Mastalgia: A Randomized, Double-Blind, Controlled Trial

Abstract

Recently evening primrose oil has been a popular holistic recommendation for the treatment of mastalgia because of its ability to affect prostaglandin metabolism. To investigate the ability of evening primrose oil to alleviate symptoms of mastalgia, the authors conducted a randomized, double-blind clinical trial. Fish oil was included in the study because it also is known to produce changes in prostaglandin metabolism. Control oils were corn oil and wheat germ oil, which were chosen for their common usage and similarity in color to the study oils. Participants for the study were recruited in Holland from 1993 through 1996 through an extensive publicity campaign involving general practitioners, surgeons, patient organizations, Dutch magazines, and posted advertisements. Women who enrolled in the study met these five criteria: cyclic or noncyclic mastalgia for more than 6 months, a minimum of 5 days and a median of at least 7 days of pain per menstrual cycle, age between 18 and 45 years, premenopausal state, and at least one functioning ovary. One hundred twenty women, 94 with cyclic and 26 with noncyclic mastalgia, enrolled in the study. Their mean age was 37.6 years. After the first clinical visit, all patients began keeping a daily pain diary, which included days with pain, severity of pain, and menstrual periods. At 3 months participants returned for a second evaluation. The 120 women recorded a mean number of 70.5 pain days in the 3-month period. On a scale of 1 to 3, the mean severity of pain was 1.64. At this time the patients were randomly assigned to one of four treatment groups that received daily regimens of 3 g of two different treatment oils. The first group received fish oil and control oil (FC); the second, evening primrose oil and control oil (EC); the third, fish oil and evening primrose oil (EF); and the fourth, two control oils (CC). Twelve women dropped out of the trial: eight because of adverse side effects, one for treatment failure, one because she became pregnant, and two because their symptoms had improved. Fifteen patients took fewer than the prescribed numbers of pills, including seven who took less than half of the doses. Eleven women complained of side effects, and four had difficulty taking or remembering pills. Side effects of treatments and placebos included gastric and abdominal symptoms, skin complaints, and weight gain. Women taking fish oil had the most trouble with gastric symptoms (belching, nausea, acidity, pain, fullness, and vomiting); 43% of those in the FC group and 60% of those in the EF group had these problems, compared with 20% and 27% of those in the EC and CC groups, respectively (P <.001). Other side effects were fairly evenly distributed. All patients experienced a decrease in the number of pain days. Fish oil registered a 15.5% decrease in pain days compared with 10.6% for its control oil, and evening primrose oil had a 12.3% decrease, compared with 13.8% for its control oil. The differences were not statistically significant. A slight decrease in severity of pain was reported by the women in all groups (0.06% to 0.08%).