Ingredient Guide
Epimedium Explained: Icariin, Tradition and the Human Evidence
Also known as horny goat weed, epimedium is a traditional herb rich in icariin and related flavonoids. What it contains, what the human studies found, and how much is in Clarity Capsules.
Explore Focus SupportEpimedium on the Label
Exactly how much epimedium is in our product, straight from the label.
How to use it (label directions): two capsules daily, taken in the morning with or without food. Each bottle holds 30 servings. How this compares with research doses: human studies used extracts described by their flavonoid content, such as 60 mg of icariin a day or 740 mg of a prenylflavonoid extract. Our label states 200 mg of epimedium extract without an icariin figure, so the amounts are not directly comparable. Use it as directed on the label.
An Old Herb, Newly Studied
Epimedium is a genus of about 52 low-growing plants in the barberry family, native mostly to China. In traditional Chinese medicine it is called yin yang huo, and in English it is widely known as horny goat weed, a name that reflects its long use for vitality and libido. Gardeners know the same plants as barrenwort or bishop's hat.
Modern research focuses on its prenylflavonoids, especially icariin, of which more than 260 related compounds have been identified across the genus. We include 200 mg of epimedium extract in Clarity Capsules, our daily focus and vitality formula, alongside maca, bacopa, rhodiola, lion's mane and huperzine A.
Tip: Most of what you read about icariin comes from cell and animal studies. The human evidence for epimedium is much smaller.
How Epimedium Works
Prenylflavonoids and Their Metabolites
Icariin and its relatives are flavonoids with an extra prenyl group attached. Icariin itself is poorly absorbed. In a human trial, after women took an epimedium prenylflavonoid extract, icariin was below detection in the blood, while its gut metabolites desmethylicaritin, icaritin and icariside II were present. These metabolites are likely responsible for much of the activity.
Hormone Signaling
Several epimedium flavonoids act weakly on estrogen receptors, which is why they are described as phytoestrogens. Epimedium does not contain hormones itself.
Bone, Blood Vessels and Antioxidant Defenses
Reviews of the laboratory research describe effects of icariin on bone-building and bone-resorbing cells, on blood vessel function and nitric oxide, on inflammatory signaling and on antioxidant defenses. These are mechanisms seen mainly in cells and animals, not proven outcomes in people.
What Human Studies Found
Bone Density After Menopause
The longest human trial ran for 24 months in 100 healthy women in late menopause with lower than average bone density. Those taking an epimedium flavonoid extract (including 60 mg of icariin a day) maintained their bone mineral density at the spine and hip, while the placebo group lost about 2 percent. The extract did not thicken the lining of the womb, a key safety check for anything with estrogen-like activity.
Safety and Absorption
A 6 week randomized trial in healthy women past menopause gave 740 mg a day of an epimedium prenylflavonoid extract. It caused no significant side effects and no changes in liver, blood or kidney tests, and it raised a marker of bone formation. It also confirmed that the metabolites, not icariin itself, are what reach the blood.
Traditional Uses
Epimedium is best known for its traditional use for vitality and libido. Controlled human research on those uses is limited, so we describe it as a traditional vitality herb rather than making promises about specific effects.
The honest summary: epimedium has a long traditional history and a large body of laboratory research. In people, the best evidence is for bone density in women after menopause, from extracts with a stated icariin content. It is one supporting botanical in Clarity Capsules, not a stand-alone solution.
Epimedium vs Maca
Epimedium and maca are the two traditional vitality herbs in Clarity Capsules, but they are very different plants.
| Feature | Epimedium | Maca |
|---|---|---|
| What it is | Leafy herb in the barberry family | Root vegetable from the Andes |
| Traditional use | Vitality and libido in Chinese medicine | Energy, stamina and libido in Peru |
| Key compounds | Prenylflavonoids such as icariin | Macamides, glucosinolates |
| Hormone activity | Weak estrogen-like activity from some flavonoids | Contains no hormones |
| In Clarity Capsules | 200 mg extract | 200 mg root extract |
Dosage, Timing, and Stacking
Amounts Used in Studies
Human studies describe their extracts by flavonoid content, for example 60 mg of icariin a day or 740 mg of a prenylflavonoid extract. Clarity Capsules provide 200 mg of epimedium extract per serving, without a stated icariin figure, so follow the label.
Timing
The Clarity Capsules label says two capsules daily in the morning, with or without food.
Stacking
In Clarity Capsules, epimedium sits with maca for vitality, bacopa and lion's mane for memory and focus, rhodiola for mental stamina and huperzine A for acetylcholine. Avoid adding a separate high-dose horny goat weed product on top without checking with your clinician.
Safety and Side Effects
In the published trials, epimedium flavonoid extracts were well tolerated, with no significant side effects over 6 weeks or 24 months.
Points Worth Knowing
- Liver: there are reports of liver injury linked to some epimedium products, so stop taking it and speak with a clinician if you notice unusual tiredness, dark urine or yellowing of the skin.
- Hormone-sensitive conditions: because some flavonoids act weakly on estrogen receptors, people with hormone-sensitive conditions should ask first.
- Medications: laboratory work shows effects on blood vessels, so ask your clinician if you take blood pressure medication or any other regular medication.
Who should be cautious: speak with a qualified healthcare professional before using epimedium if you are pregnant or nursing, have a liver or hormone-sensitive condition, or take blood pressure or any other regular medication.
Key Takeaways
- Epimedium (horny goat weed) is a traditional Chinese herb rich in prenylflavonoids such as icariin.
- Icariin is poorly absorbed; its gut metabolites are what reach the blood.
- The strongest human evidence is a 24 month trial showing maintained bone density in women after menopause.
- Clarity Capsules contain 200 mg of epimedium extract per serving, with no stated icariin content.
- Check with a clinician if you have a liver or hormone-sensitive condition or take regular medication.
Tradition, Checked Against Evidence.
Epimedium has centuries of traditional use and a growing body of laboratory research. We include it as one supporting botanical in a daily formula and describe it by what the human studies show.
Epimedium FAQ
What does epimedium do for you?
Epimedium is a traditional Chinese herb used for vitality, energy and libido. Its key compounds are prenylflavonoids such as icariin. Laboratory research shows effects on hormone signaling, bone cells, blood vessels and antioxidant defenses, and a 24 month trial in women past menopause found an epimedium flavonoid extract helped maintain bone mineral density. Human research on other uses is limited.
Is epimedium the same as horny goat weed?
Yes. Horny goat weed is a common name for Epimedium, a genus of about 52 plant species. Other names include yin yang huo, barrenwort and bishop's hat.
What is icariin?
Icariin is the best known prenylflavonoid in epimedium. It is poorly absorbed in its original form; after you take epimedium, the gut converts it into related compounds such as icariside II and icaritin, which are what show up in the blood.
How much epimedium is in Clarity Capsules?
Each 2-capsule serving of Clarity Capsules contains 200 mg of epimedium extract, alongside lion's mane, maca, bacopa, rhodiola and huperzine A. The label does not state icariin content, so the amount cannot be compared directly with study extracts.
Is epimedium safe?
In a 6 week trial in healthy women past menopause, 740 mg a day of an epimedium prenylflavonoid extract caused no significant side effects and no changes in liver, blood or kidney tests. There are reports of liver injury linked to some epimedium products, and its flavonoids have weak estrogen-like activity, so people with liver or hormone-sensitive conditions, and anyone who is pregnant, nursing or taking medication, should check with a clinician first.
Does epimedium contain hormones?
No. Epimedium does not contain hormones, but some of its flavonoids act weakly on estrogen signaling, which is why they are called phytoestrogens.
More on Epimedium
Related guides
Sources
- Ma H, et al. The genus Epimedium: an ethnopharmacological and phytochemical review. Journal of Ethnopharmacology, 2011. PubMed 21215308
- He C, et al. Pharmacological effects of icariin. Advances in Pharmacology, 2020. PubMed 32089233
- Zhang G, et al. Epimedium-derived phytoestrogen flavonoids exert beneficial effect on preventing bone loss in late postmenopausal women: a 24-month randomized, double-blind and placebo-controlled trial. Journal of Bone and Mineral Research, 2007. PubMed 17419678
- Yong EL, et al. Randomized, double-blind, placebo-controlled trial to examine the safety, pharmacokinetics and effects of Epimedium prenylflavonoids, on bone specific alkaline phosphatase and the osteoclast adaptor protein TRAF6 in post-menopausal women. Phytomedicine, 2021. PubMed 34352588
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Nothing here is medical advice. If you are pregnant, nursing, taking medication, or managing a liver or hormone-sensitive condition, consult a qualified healthcare professional before use.