]>
IRCT20181125041749N2 IRCT 2026-08-11 Alzahra University Effect of Evening Primrose Oil supplementation on menstrual pain, mastalgia, menstrual distress, fatigue and anaerobic capacity in physically active women with primary dysmenorrhea: A single-center, randomized, double-blind, placebo-controlled trial Effect of Evening Primrose Oil supplementation on menstrual pain, mastalgia, menstrual distress, fatigue and anaerobic capacity in physically active women with primary dysmenorrhea: A single-center, randomized, double-blind, placebo-controlled trial 2026-11-21 anticipated 28 Pending https://irct.ir/trial/92391 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Used, Assignment: Parallel, Purpose: Treatment, Randomization description: After assessing the inclusion and exclusion criteria, completing the Physical Activity Readiness Questionnaire (PAR-Q), and obtaining written informed consent, eligible participants will be randomly allocated using simple randomization to two equal groups: an intervention group receiving evening primrose oil (EPO) and a control group receiving placebo. The unit of randomization will be the individual participant, and randomization will be performed at the individual level. To generate the randomization sequence, each participant will be assigned a unique identification code, and participants will be allocated to the two groups using a random number table. Fourteen participants will be allocated to each group. No stratified or cluster randomization will be used in this study. To ensure allocation concealment, the group codes will be generated and maintained by a third party who will not be involved in participant assessment, intervention delivery, or data analysis. The EPO and placebo capsules will be identical in appearance, size, color, packaging, and administration procedure and will be packaged using identical, non-identifiable codes. The participants and researchers responsible for conducting the assessments will remain unaware of group assignments. The allocation codes will remain confidential until completion of data collection and statistical analysis and will then be unblinded, Blinding description: After random allocation, the group codes will be generated and maintained by a third party who will not be involved in participant assessment, intervention delivery, or data analysis. The evening primrose oil and placebo capsules will be identical in appearance, size, color, packaging, and administration procedure and will be provided using non-identifiable codes. Participants will be blinded to the intervention they receive. Researchers and outcome assessors will also remain unaware of the participants’ group assignments throughout data collection. The allocation codes will remain confidential until completion of the statistical analysis and will then be unblinded. If data analysis is performed using coded group assignments, the data analyst will also remain blinded to group allocation. N/A Primary dysmenorrhea. Intervention 1: Intervention group: Participants will receive one capsule of evening primrose oil (EPO) containing 1000 mg (containing 8%–14% gamma-linolenic acid (GLA)) daily. The capsule will be taken for 8 weeks, starting on the fifth day of the menstrual cycle, with food and a glass of water. The product will be obtained from a reputable pharmaceutical company licensed by the Food and Drug Administration. The composition and specifications of the product will be in accordance with the information provided by the manufacturer. Intervention 2: Control group: articipants will receive one placebo capsule containing 1000 mg of soybean oil daily. The placebo capsules will be identical to the evening primrose oil capsules in appearance, size, color, packaging, and administration procedure and will contain no gamma-linolenic acid (GLA). The capsules will be taken for 8 weeks, starting on the fifth day of the menstrual cycle, with food and a glass of water. Yes - There is a plan to make this available What will be shared: Data relating to subjects will be shared as unidentified. When: Six months after the publication of the article. To whom: All researchers Conditions: The data may be used for citation purposes, provided that the source is acknowledged. Where to obtain: Fahimeh Kazemi How to obtain: By an Email Comments:
public Fahimeh Kazemi
Faculty of Physical Education and Sport Sciences, Alzahra University, Deh-e Vanak St
Tehran Iran (Islamic Republic of) ۱۹۹۳۸۹۳۹۷۳ +98 21 8569 2689 f.kazemi@alzahra.ac.ir Alzahra University scientific Fahimeh Kazemi
Faculty of Physical Education and Sport Sciences, Alzahra University, Deh-e Vanak St
Tehran Iran (Islamic Republic of) ۱۹۹۳۸۹۳۹۷۳ +98 21 8569 2689 f.kazemi@alzahra.ac.ir Alzahra University Iran (Islamic Republic of) Age 18–35 years Regular menstrual cycles (21–35 days) Menstrual pain score ≥4 based on the Visual Analog Scale (VAS) in two consecutive menstrual cycles, according to the DSM-IV-TR criteria for primary dysmenorrhea Regular physical activity, defined as at least three sessions per week of ≥30 minutes of moderate-to-vigorous intensity physical activity during the previous 6 months Provision of a normal pelvic ultrasonography report obtained within the previous 6 months to rule out secondary causes of dysmenorrhea and confirm the absence of structural abnormalities of the uterus and ovaries, including endometriosis, adenomyosis, uterine fibroids, endometrial polyps, and pathological ovarian cysts No use of hormonal medications, including oral contraceptive pills (OCPs), during the 3 months preceding the study No use of nonsteroidal anti-inflammatory drugs (NSAIDs), antioxidants, other oil-based supplements, or herbal medicines affecting menstruation during the 4 weeks preceding the study Willingness to participate in the study and provision of written informed consent 18 years 35 years Female Presence of secondary dysmenorrhea or a known structural pelvic disorder, including endometriosis, adenomyosis, uterine fibroids, endometrial polyps, or pathological ovarian cysts Presence of systemic diseases, including diabetes, thyroid disorders, liver or kidney diseases, or severe psychiatric disorders Current use of hormonal medications, including oral contraceptive pills (OCPs) Current use of medications or supplements that may affect menstrual symptoms, including nonsteroidal anti-inflammatory drugs (NSAIDs), antioxidants, oil-based supplements, or herbal medicines Known allergy or hypersensitivity to evening primrose oil (EPO) or any of its components Pregnancy or breastfeeding at the time of enrollmentAny medical condition that contraindicates participation in moderate-to-vigorous physical activity N94.4 Primary dysmenorrhea Treatment - Other N/A Intervention group: Participants will receive one capsule of evening primrose oil (EPO) containing 1000 mg (containing 8%–14% gamma-linolenic acid (GLA)) daily. The capsule will be taken for 8 weeks, starting on the fifth day of the menstrual cycle, with food and a glass of water. The product will be obtained from a reputable pharmaceutical company licensed by the Food and Drug Administration. The composition and specifications of the product will be in accordance with the information provided by the manufacturer. Control group: articipants will receive one placebo capsule containing 1000 mg of soybean oil daily. The placebo capsules will be identical to the evening primrose oil capsules in appearance, size, color, packaging, and administration procedure and will contain no gamma-linolenic acid (GLA). The capsules will be taken for 8 weeks, starting on the fifth day of the menstrual cycle, with food and a glass of water. Menstrual pain intensity. Timepoint: On the second day of the menstrual cycle at baseline before initiation of the intervention, on the second day of the subsequent menstrual cycle after initiation of the intervention, and on the second day of the following menstrual cycle. Method of measurement: A 10-cm Visual Analogue Scale for pain intensity, ranging from 0 indicating no pain to 10 indicating the most severe pain imaginable. Menstrual-related mastalgia intensity. Timepoint: During the luteal phase of the menstrual cycle at baseline before initiation of the intervention, during the luteal phase of the subsequent menstrual cycle after initiation of the intervention, and during the luteal phase of the following menstrual cycle. Method of measurement: A Numerical Rating Scale for pain intensity ranging from 0 indicating no pain to 10 indicating the most severe pain imaginable. Menstrual distress severity. Timepoint: At the end of the menstrual cycle at baseline, at the end of the subsequent menstrual cycle after initiation of the intervention, and at the end of the following menstrual cycle. Method of measurement: The 42-item Moos Menstrual Distress Questionnaire, with a total score ranging from 0 to 168. Mental fatigue score. Timepoint: At the end of the menstrual cycle at baseline, at the end of the subsequent menstrual cycle after initiation of the intervention, and at the end of the following menstrual cycle. Method of measurement: The 20-item Multidimensional Fatigue Inventory assessing general fatigue, physical fatigue, mental fatigue, reduced motivation, and reduced activity. Anaerobic capacity. Timepoint: On days 7 to 10 of the follicular phase at baseline, on days 7 to 10 of the follicular phase of the subsequent menstrual cycle after initiation of the intervention, and on days 7 to 10 of the follicular phase of the following menstrual cycle. Method of measurement: The Running-Based Anaerobic Sprint Test consisting of six 35-meter maximal sprints with 10 seconds of rest between sprints; peak power, mean power, and fatigue index are calculated. Alzahra University Approved 2026-06-30 Research Ethics Committees of Alzahra University Alzahra University, Deh-e-Vanak St. Tehran Tehran Iran (Islamic Republic of)