The BioCycle study was designed to investigate oxidative stress levels across the menstrual cycle in healthy women age 18–44 [13 (link)] who were followed for one (n = 9) or two menstrual cycles (n = 250). The study design, procedures, and participants have been described in detail elsewhere [14 (link)]. The Health Sciences Institutional Review Board at the University at Buffalo approved the study and served as the Institutional Review Board designated by the National Institutes of Health under a reliance agreement. All study participants provided written, informed consent prior to any study procedures. The participants were regularly menstruating premenopausal women recruited from western New York. Other inclusion criteria included a self-reported body mass index (BMI) at screening between 18 and 35 kg/m2, not planning to consume a restricted diet for intended weight loss or medical reasons and willingness to discontinue any supplement, vitamin, or antioxidant use during the study period [14 (link)]. Study visits were scheduled to occur up to eight times per cycle during the key phases of the menstrual cycle with visits timed using fertility monitors [15 (link)] to correspond to menstruation, the middle of the follicular phase, time of estrogen peak, time of the luteinizing hormone and follicle-stimulating hormone surge, the day of expected ovulation, time of progesterone elevation and peak, and prior to menstruation. The home fertility monitors measured urinary estrone-3-glucuronide and luteinizing hormone (LH). When the monitor indicated an LH surge, the participants were instructed to return to the clinical site for a blood draw. Participants were highly compliant with the study protocol, and 94 % of women completed seven or eight visits per cycle, which included blood sampling and questionnaires.
On four of the study visits, corresponding to menses, mid-follicular phase, expected ovulation, and mid-luteal phase, participants completed 24-h dietary recalls. 96 % of participants completed at least three 24-h dietary recalls in each of their two cycles, and 73 % completed all eight 24-h dietary recalls. Women with fewer than four recalls per menstrual cycle were not different by age, BMI, or other demographic characteristics. 32 % of the 24-h recalls were conducted on the weekends with the largest proportion of weekend visits occurring on the peri-ovulatory phase visits. The dietary intake data were collected and analyzed using the Nutrition Data System for Research by the Nutrition Coordinating Center, University of Minnesota, Minneapolis, MN. On those same study visits, a questionnaire regarding 17 menstrual symptoms and the severity of those symptoms in the previous week was completed, which included the assessment of women’s food cravings throughout the menstrual cycle (craving questionnaires were complete for 97 % of clinic visits). Symptom severity was ranked as none, mild, moderate, or severe. At the baseline visit, a trained research assistant measured height, weight, and waist circumference at the natural waist using standardized protocols. Information regarding age, BMI, race, education, cigarette smoking, and habitual physical activity was also collected at baseline. Physical activity was measured using the International Physical Activity Questionnaire [16 (link)]. Anovulatory cycles were defined as cycles where the peak progesterone concentration across the cycle was ≤5 ng/mL, and there was no serum LH peak on the later cycle visits (n = 42 cycles) [17 , 18 (link)].
On four of the study visits, corresponding to menses, mid-follicular phase, expected ovulation, and mid-luteal phase, participants completed 24-h dietary recalls. 96 % of participants completed at least three 24-h dietary recalls in each of their two cycles, and 73 % completed all eight 24-h dietary recalls. Women with fewer than four recalls per menstrual cycle were not different by age, BMI, or other demographic characteristics. 32 % of the 24-h recalls were conducted on the weekends with the largest proportion of weekend visits occurring on the peri-ovulatory phase visits. The dietary intake data were collected and analyzed using the Nutrition Data System for Research by the Nutrition Coordinating Center, University of Minnesota, Minneapolis, MN. On those same study visits, a questionnaire regarding 17 menstrual symptoms and the severity of those symptoms in the previous week was completed, which included the assessment of women’s food cravings throughout the menstrual cycle (craving questionnaires were complete for 97 % of clinic visits). Symptom severity was ranked as none, mild, moderate, or severe. At the baseline visit, a trained research assistant measured height, weight, and waist circumference at the natural waist using standardized protocols. Information regarding age, BMI, race, education, cigarette smoking, and habitual physical activity was also collected at baseline. Physical activity was measured using the International Physical Activity Questionnaire [16 (link)]. Anovulatory cycles were defined as cycles where the peak progesterone concentration across the cycle was ≤5 ng/mL, and there was no serum LH peak on the later cycle visits (n = 42 cycles) [17 , 18 (link)].
