Mullein Leaf and Male Fertility
There is no evidence that mullein leaf affects male fertility—neither beneficial nor harmful effects have been documented in the scientific literature or clinical guidelines. 1
Evidence Assessment
The WHO guidelines on male infertility comprehensively reviewed herbal therapies and their effects on male reproductive function, but mullein leaf (Verbascum species) was not identified or studied in any of the analyzed trials. 1
What We Know About Herbal Therapies Generally
The available evidence on herbal treatments for male infertility is limited to specific plants that have been studied:
Studied herbal therapies include ginseng, saffron, Nigella sativa, palm pollen, sesame, and Mucuna pruriens, but mullein is notably absent from this list. 2
Quality of herbal therapy evidence is very low, with significant methodological problems including lack of standardization, heterogeneity in study design, and insufficient reporting of pregnancy outcomes or live births. 1
The WHO strongly recommends that there are insufficient data to recommend the use of herbal therapies for treatment of men with abnormal semen parameters and/or male infertility, based on very low quality evidence. 1
Clinical Implications for Mullein Leaf Specifically
Since mullein leaf has not been studied in the context of male fertility:
No documented benefits on sperm parameters (concentration, motility, morphology) exist in the peer-reviewed literature. 1
No documented harms on reproductive hormones or semen quality have been reported. 1
No data on pregnancy outcomes (clinical pregnancy rates or live births) are available for men using mullein leaf. 1
Important Caveats
The absence of evidence is not evidence of safety. Men attempting to conceive should be counseled that:
Herbal supplements are not regulated with the same rigor as pharmaceutical medications and may contain unlisted ingredients or contaminants. 1
The WHO guidelines emphasize that men trying for pregnancy should focus on proven modifiable factors such as smoking cessation, weight optimization, and avoiding recreational drugs rather than unproven herbal supplements. 3
Any man with fertility concerns should undergo proper evaluation including medical history, physical examination, and semen analysis rather than self-treating with herbal products. 1
Practical Recommendation
If a man is currently using mullein leaf and experiencing fertility difficulties, discontinuation is reasonable given the lack of proven benefit and the principle of eliminating unnecessary exposures during conception attempts, though there is no specific evidence of harm. 1 Priority should be given to addressing documented risk factors like obesity, smoking, and heat exposure that have established negative effects on male fertility. 1