Supplement × Supplement·a caution·Moderate evidence
St. John's Wort can alter drug metabolism and hormonal contraceptive effectiveness, complicating Vitex use for cycle symptoms.
Every entry follows the same shape: what is happening, the mechanism, and the recommendation.
What is happening. St. John's Wort can alter drug metabolism and hormonal contraceptive effectiveness, complicating Vitex use for cycle symptoms.
Mechanism. CYP and P-gp induction plus hormonal and neurotransmitter effects.
Recommendation. Avoid unsupervised combination, especially with contraception, antidepressants, or hormone therapy.
Effect on the composite score
If both St. John's Wort and Vitex (Chasteberry) are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are at /methodology/stack-score.
Every claim on this page is cited. PMIDs link straight to PubMed.
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NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.
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