A double-blind, placebo-controlled trial of Fennel (Foeniculum vulgare) on menopausal symptoms: A high placebo response

OBJECTIVE: The present study aimed to evaluate the effects of oral fennel on menopausal symptoms. MATERIAL AND METHODS: This double-blind, randomized, placebo-controlled trial was conducted on 50 postmenopausal women in Mashhad (Iran). Patients were randomly divided into two groups of fennel (n=25) and placebo (n=25). Measurements were performed at baseline and after three months using the Menopause-Specific Quality of Life questionnaire. RESULTS: Both placebo and treatment groups revealed significant improvements in the hot flush score (p<0.001 for fennel and p<0.01 for placebo), night sweats (p=0.007 for fennel and p<0.01 for placebo), sweating (p=0.002 for fennel and p<0.01 for placebo), symptoms of anxiety (p=0.05 for fennel and p=0.001 for placebo), feeling depressed (p<0.01 for fennel and p=0.006 for placebo), and impatience with other people (p<0.01 for fennel and p=0.003 for placebo). There were no significant differences in any menopausal symptoms between the fennel and placebo groups, except for coughing and sneezing when urinating (p=0.03). CONCLUSION: The failure to indicate a significant effect may have been caused by a high placebo response. It is suggested that future trials should include a placebo run-in phase or design a sequential, parallel study with larger sample sizes to mitigate the placebo effect.