Outcome
    Limited
    Effectiveness 1/5

    Chrysin for Aromatase Inhibition

    Chrysin is a flavonoid that inhibits aromatase (CYP19) potently in vitro, which made it a staple of 1990s-2000s testosterone-booster formulas. Human pharmacokinetic work then showed chrysin is glucuronidated and sulfated almost completely during first-pass metabolism, with free plasma chrysin orders of magnitude below the concentrations needed for aromatase inhibition. Controlled human studies confirm no change in testosterone, estrogen, or body composition.

    Overview

    Chrysin is a flavonoid that inhibits aromatase (CYP19) potently in vitro, which made it a staple of 1990s-2000s testosterone-booster formulas. Human pharmacokinetic work then showed chrysin is glucuronidated and sulfated almost completely during first-pass metabolism, with free plasma chrysin orders of magnitude below the concentrations needed for aromatase inhibition. Controlled human studies confirm no change in testosterone, estrogen, or body composition.

    Verdict

    Not supported

    Chrysin inhibits aromatase in cell cultures but is so rapidly metabolized in humans that oral doses produce no measurable anti-estrogenic effect.

    How It Works

    Binds the aromatase active site in vitro, but first-pass conjugation prevents bioactive concentrations from ever being reached in human tissues.

    Dosing & Protocol

    Typical dose

    Recommended dose
    No effective oral dose exists
    Expected timeframe
    Not applicable - ineffective orally

    Protocol

    cycle
    N/A
    timing
    N/A

    Evidence

    What the studies say

    Cell-culture aromatase inhibition is real but irrelevant at achievable human blood levels. Human trials using 1-3 g/day (including in athletes) found no hormonal changes. This is one of the clearest examples in supplement science of in-vitro promise failing in humans due to bioavailability.

    Evaluation of the mutagenic activity of chrysin, a flavonoid inhibitor of the aromatization process

    Score: 5/10
    2012
    observational

    Oliveira GA, Ferraz ER, Souza AO +2 more

    The MN test showed that from 1 to 15 microM of this flavonoid mutagenic activity was noted in HepG2 cells.

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    Developing nutritional component chrysin as a therapeutic agent: Bioavailability and pharmacokinetics consideration, and ADME mechanisms

    Score: 7/10
    2021
    systematic_review

    Gao S, Siddiqui N, Etim I +2 more

    Although chrysin's biological activities have been demonstrated and the mechanism of actions has been determined using in vitro and in vivo models, results from the current clinical studies were largely negative.

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    Effects of androstenedione-herbal supplementation on serum sex hormone concentrations in 30- to 59-year-old men

    Score: 7/10
    2001
    rct
    n=55

    Brown GA, Vukovich MD, Martini ER +2 more

    Serum concentrations of total testosterone and PSA were unchanged by supplementation. DION increased (p < 0.05) serum androstenedione (342%), free testosterone (38%), dihydrotestosterone (71%), and estradiol (103%) concentrations.

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    Effects of chrysin on urinary testosterone levels in human males

    Score: 4/10
    2003
    observational
    n=20

    Gambelunghe C, Rossi R, Sommavilla M +5 more

    Oral chrysin did not produce meaningful changes in urinary testosterone levels in men.

    View source

    Safety

    Caveats

    Spending money on chrysin for hormonal effects is not supported by human evidence.

    Less likely to help if

    Everyone - oral chrysin has almost no bioavailability and does not change oestrogen or testosterone in humans.

    Medical Disclaimer

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    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.