Objectives: To examine the efficacy of a hop extract (standardized at 100 [micro]g 8-prenylnaringenin per day) for relief of menopausal discomforts.
Methods: A 16-week randomized, double-blind, placebo-controlled, cross-over study was conducted with 36 menopausal women. The participants were randomly allocated to either placebo or active treatment (hop extract) for a period of eight weeks after which treatments were switched for another eight weeks. The Kupperman Index (KI), the Menopause Rating Scale (MRS) and a multifactorial Visual Analogue Scale (VAS) were assessed at baseline, and after eight and sixteen weeks.
Results: After 8 weeks, both active treatment and placebo significantly improved all outcome measures when compared to baseline with somewhat higher average reductions for placebo than for the active treatment. After 16 weeks only the active treatment after placebo further reduced all outcome measures, whereas placebo after active treatment resulted in an increase for all outcome measures. Although, the overall estimates of treatment efficacy (active treatment-placebo) based on linear mixed models do not show a significant effect, time-specific estimates of treatment efficacy indicate significant reductions for KI (P = 0.02) and VAS (P = 0.03) and a marginally significant reduction (P = 0.06) for MRS after 16 weeks.
Conclusions: Whereas the first treatment period resulted in similar reductions in menopausal discomforts in both treatment groups, results from the second treatment period suggest superiority of the standardized hop extract over placebo. Thus, phytoestrogen preparations containing this standardized hop extract may provide an interesting alternative to women seeking relief of mild vasomotor symptoms.
Keywords: Menopause Phytoestrogens Hop (Humulus lupulus L.) Kupperman index Visual analogue scale Menopause rating scale
The interest in the use of phytoestrogens for the management of menopausal complaints has increased considerably since the widely publicized and discussed results of the Women's Health Initiative and the One Million Women Study. Phytoestrogens are mostly non-steroidal polyphenolic plant-derived compounds that functionally mimic the activity of the human estrogen, 17[beta]-estradiol and typical sources include soy and red clover (isoflavones), flaxseed (lignans) and hops (prenylflavonoids) (Cos et al., 2003). A large body of scientific evidence from both epidemiological and experimental studies suggests that the consumption of phytoestrogen-rich diets may have protective effects on estrogen-related conditions, such as menopausal symptoms (Huntley and Ernst, 2004), and estrogen-related diseases, such as prostate and breast cancers (Holzbeierlein et al., 2005; Wu et al., 2008), osteoporosis (Messina et al., 2004; Ye et al., 2006), and cardiovascular diseases (Clerici et al., 2007). On the other hand, systematic reviews of randomized, controlled trials (RCTs) show contradictory results and meta-analyses failed to demonstrate a statistically significant reduction of vasomotor symptoms for phytoestrogens (Krebs et al., 2004; Kronenberg and Fugh-Berman, 2002; Lethaby et al., 2007). In more selected patient populations, however, such as in women in early natural menopause with mild to moderate vasomotor symptoms, a systematic review found a significant reduction of hot flashes in five out of five RCTs (Tempfer et al., 2007). It should be noticed that intervention studies with phytoestrogens suffer from large variabilities in outcome...