Enel Health®Atlas
Sign in
Enel Health®Atlas
Browse libraries

Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

Chrysin

Chrysin (5,7-Dihydroxyflavone), the Bodybuilding 'Natural Aromatase Inhibitor'

Evidence grade 1 of 5, Untested. Read how the Atlas grades evidence.

The written rationale for this grade is still being prepared.

FDA
Not FDA approved; sold as a dietary supplement

Reference only. Not medical advice.

What can go wrong

Chrysin appears low in acute toxicity, but the meaningful risk is economic and behavioral: men take it expecting an anti-estrogen or testosterone effect it does not deliver, potentially delaying evaluation of real hypogonadism or gynecomastia. Because it is a common label ingredient in 'test booster' blends, it also lends false credibility to those products. Aromatase inhibition, if it were achieved, carries its own risks (bone, lipid, mood).

This is something to take to a clinician. The Atlas can tell you what is known about chrysin in general. It cannot tell you what is happening in your body, and the difference matters most for exactly the symptoms that bring people to this page.

Chrysin is a flavone from passionflower and honey/propolis long sold to bodybuilders as a 'natural aromatase inhibitor' to block testosterone-to-estrogen conversion and thereby raise free testosterone. It is indeed one of the more potent flavonoid aromatase inhibitors in vitro. The problem is bioavailability: oral chrysin is absorbed at under 1% and rapidly conjugated and excreted, and human studies show it does not meaningfully change estrogen or testosterone. It is a canonical example of in-vitro potency failing completely in vivo.

A potent aromatase inhibitor in a test tube that does essentially nothing when swallowed.

What people take it for

These are the reasons people give for taking it. They are not effects it has been shown to have.

  • Purported aromatase inhibition / 'estrogen blocking'
  • Testosterone support (claimed)
  • Post-cycle and bodybuilding stacks

Combinations named above are how people use these compounds together, under names the community gave them. The combinations themselves have not been studied. Evidence for one compound is not evidence for a pair.

How it is supposed to work

In cell and enzyme assays chrysin inhibits aromatase (CYP19), the enzyme converting androgens to estrogens, which is the theoretical basis for raising testosterone and lowering estradiol. That mechanism is real in vitro but irrelevant in practice because so little intact chrysin reaches systemic circulation after oral dosing.

Why the test tube lies

Chrysin is extensively glucuronidated and sulfated in the gut wall and liver, so oral bioavailability is below 1% and the free plasma concentrations needed to inhibit aromatase are never achieved. Human studies confirm no significant effect on estrogen or testosterone. Some products add piperine or use delivery tricks to boost absorption, but there is still no convincing human evidence of a hormonal effect.

What people get wrong

  • Often saidChrysin naturally lowers estrogen and raises testosterone

    ActuallyOral bioavailability under 1% means it does not measurably affect hormones in humans; the in-vitro potency is a marketing artifact.

  • Often saidAdding piperine makes it work

    ActuallyAbsorption enhancers may raise levels somewhat, but there is still no convincing human evidence of a hormonal effect.

Who profits, and who pushes back

Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.

Set against the alternatives

Prescription aromatase inhibitors (anastrozole, letrozole) genuinely lower estrogen and are used off-label in some hypogonadal men under supervision; chrysin is not a natural equivalent, it is an inactive oral mimic. Apigenin and quercetin share the same in-vitro-only aromatase story.

What we do not know

  • Is there any delivery technology that makes oral chrysin hormonally active?
  • Why does it persist in the market despite decades of negative human data?

The market for this

What follows describes how this is bought and sold. It is not a buying guide and it is not an endorsement of any seller.

Chrysin is extracted from Passiflora or produced synthetically; purity is generally acceptable, but no formulation reliably overcomes the fundamental bioavailability barrier, making 'high potency' claims largely meaningless for the intended effect.

At a glance

Oral bioavailability
<1%
In-vitro
Potent aromatase (CYP19) inhibitor
In-vivo human effect
No meaningful change in T or estrogen

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about Chrysin. A short entry is not a safe entry.

  • Timeline. We have not built the dated record of research and regulatory events.
  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • Children and teenagers. We have not checked what is known about younger people.
  • Where we land. We have not taken a position on this yet.

Sources

The studies below are named and described, but not linked. You cannot open them from here and check our reading against them, which means this page is our summary of the literature rather than a document you can verify. Weigh it accordingly until the links exist.

The studies that matter

  • Saarinen et al., aromatase inhibition by methylated flavones2001

    Chrysin potent in vitro; poor bioavailability limits in-vivo activity

  • Human oral chrysin exposure studiesvarious

    Absorption <1%; no significant change in estrogen/testosterone

  • Systematic review of chrysin and CYP192020

    Confirms in-vitro aromatase inhibition that does not translate clinically