NutriStack
Estradiol and St. John's Wort, a conflict.
St. John's Wort induces CYP3A4, which metabolizes estradiol. This can reduce estradiol levels by 20-40%, potentially causing breakthrough bleeding, hot flashes, or loss of menopausal symptom control.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Estradiol and St. John's Wort
- Pair type
- Conflict
- Evidence (highest tier)
- Strong
- Source citations
- 1 source
- Stack Score effect
- −10 to your Stack Score (per scored conflict row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Conflict · Strong evidence
Conflict
What is happening. St. John's Wort induces CYP3A4, which metabolizes estradiol. This can reduce estradiol levels by 20-40%, potentially causing breakthrough bleeding, hot flashes, or loss of menopausal symptom control.
Mechanism. Estradiol is metabolized by CYP3A4 (2-hydroxylation) and CYP1A2. SJW induces CYP3A4, increasing estradiol clearance and reducing plasma levels.
Recommendation. Avoid St. John's Wort while on estradiol HRT. Breakthrough bleeding and return of menopausal symptoms may occur.
Stack Score
How this pair moves the number.
Effect on the composite score
If both Estradiol and St. John's Wort are in the same stack, this pair applies −10 to your Stack Score (per scored conflict row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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