Postural sway is not affected by estrogen fluctuations during the menstrual cycle

When people stand still, they exhibit a phenomenon called postural sway, or spontaneous movement of the body's center of pressure, which is related to balance control. In general females show less sway than males, but this difference only begins to appear around puberty, pointing to different levels of sex hormones as one potential mechanism for sway sex differences. In this study, we followed cohorts of young females using oral contraceptives (n = 32) and not using oral contraceptives (n = 19), to investigate associations between estrogen availability and postural sway. All participants visited the lab four times over the putative 28-day menstrual cycle. At each visit, we performed blood draws to measure plasma estrogen (estradiol) levels, and tests of postural sway using a force plate. During late follicular and mid-luteal phase, estradiol levels were lower in participants using oral contraceptives (mean differences [95% CI], respectively: -231.33; [-800.44, 337.87]; -613.26; [-1333.60, 107.07] pmol/L; main effect p < 0.001), reflecting expected consequences of oral contraceptive use. Despite these differences, postural sway was not significantly different between participants who were using oral contraceptives and participants who were not (mean difference: 2.09 cm; 95% CI = [-1.05, 5.22]; p = 0.132). Overall, we found no significant effects of the estimated menstrual cycle phase-or absolute levels of estradiol-on postural sway.

Effects of Blenderized Watermelon With the Rind on Satiety, Bowel Movement, and Postprandial Glucose

Objectives

Many studies have examined the beneficial effects of watermelon flesh on metabolic diseases, yet fewer studies have investigated the effects of watermelon rind. While normally discarded, rind consumption not only reduces food waste but contains fiber (pectin) and healthful bioactive compounds such as citrulline. This study examined the effects of watermelon rind consumption on postprandial glucose, satiety and bowel movements. It was hypothesized that consumption of blenderized watermelon juice with rind would lower postprandial glucose, increase satiety and improve bowel movement habits.

Methods

In a double-blind randomized crossover study, 21 participants (age 26.3 ± 5.7 y, BMI 22.6 ± 2.8 kg/m2) consumed one cup (8 fl. oz) of blenderized watermelon juice with or without rind. A visual analogue scale was used to measure satiety at baseline, immediately after, 20, 40, 60 and 90 minutes post juice consumption. Blood glucose was measured at baseline, 20, 40, 60 and 90 minutes post juice consumption. Bowel movement questionnaires were administered two days before and after each trial.

Results

Both blenderized watermelon juices (with and without rind) increased satiety with more fullness in watermelon juice with rind (P &lt; 0.05). Watermelon juice with rind also stabilized blood glucose levels in comparison to watermelon juice (P &lt; 0.001). No significant differences between the two trials for bowel movements were found, but no evidence of constipation or discomfort was presented among the participants.

Conclusions

These results suggest that watermelon juice with rind has favorable effects on postprandial glucose and satiety levels but no effect on bowel movements. Therefore, further research into the benefits of watermelon rind is important and could offer potential clinical applications and disease prevention.

Funding Sources

NUTR 302L Advanced Nutrition Laboratory San Diego State University and National Watermelon Promotion Board (NWPB 19–20).