Ingredients

One page per ingredient. Each profile covers the plausible mechanism, what human trials actually found, the dose used in that research, who should avoid it, and which products on this site contain it.

Supplement marketing tends to describe ingredients in terms of outcomes — "boosts testosterone", "increases stamina". This library describes them in terms of mechanism and evidence quality instead, because that is what lets you judge whether a claim is plausible for you specifically.

Each profile states plainly where the evidence is strong (usually micronutrient correction in deficiency), where it is moderate (adaptogens on stress and fatigue endpoints), and where it is weak or contested (several popular botanicals for testosterone in healthy men).

All ingredient profiles

Mechanism, human trial results, dose and safety — with the evidence tier stated up front.

Maca Root — Libido and energy Maca Root Lepidium meyenii Moderate evidence Panax Ginseng — Adaptogen, erectile function Panax Ginseng Panax ginseng C.A. Meyer Moderate evidence L-Arginine — Nitric oxide precursor L-Arginine Amino acid Moderate evidence Tribulus Terrestris — Libido — not testosterone Tribulus Terrestris Tribulus terrestris L. Contested evidence Zinc — Testosterone cofactor Zinc Essential trace mineral Strong evidence Vitamin D — Hormone precursor Vitamin D Cholecalciferol (D3) Strong evidence Ashwagandha — Adaptogen, cortisol Ashwagandha Withania somnifera Moderate evidence Tongkat Ali — SHBG and stress Tongkat Ali Eurycoma longifolia Moderate evidence Saw Palmetto — Prostate phytotherapy Saw Palmetto Serenoa repens Contested evidence Epimedium (Horny Goat Weed) — Icariin, PDE-5 pathway Epimedium (Horny Goat Weed) Epimedium sagittatum Limited evidence Boswellia Serrata — Joint comfort Boswellia Serrata Boswellia serrata Moderate evidence Nettle Root — SHBG binding, prostate Nettle Root Urtica dioica Moderate evidence Ginkgo Biloba — Circulation, bleeding risk Ginkgo Biloba Ginkgo biloba L. Limited evidence Selenium — Sperm quality, narrow window Selenium Essential trace mineral Strong evidence Cordyceps — Oxygen use, endurance Cordyceps Cordyceps militaris / sinensis Moderate evidence Reishi — Immune modulation, sleep Reishi Ganoderma lucidum Limited evidence Fenugreek — Libido, blood glucose Fenugreek Trigonella foenum-graecum Limited evidence

Guides in this topic

Frequently asked questions

How is evidence quality rated in these profiles?

Strong = multiple randomised controlled trials in humans with consistent direction of effect, ideally pooled in a meta-analysis. Moderate = several human trials with mixed or modest results, or consistent results in narrow populations. Limited = mainly animal or in-vitro data, or small human studies with methodological weaknesses.

Why do some ingredients work only in deficient people?

Micronutrients such as zinc and vitamin D are cofactors in enzymatic processes. Once the enzyme is saturated, adding more substrate changes nothing. That is why supplementation reliably raises testosterone in zinc-deficient men and reliably does nothing in men with adequate status.

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