A Common Mineral Gap and a Tested Stress Reliever
A genuine cofactor, and a genuinely well-tested adaptogen
These two are grouped together as moderate-evidence supplements addressing genuinely common, if less severe, gaps than vitamin D.
Zinc
Zinc is a genuine cofactor — a helper mineral a biological process needs in order to function — in testosterone synthesis and immune function; the Hormones guide covers the specific controlled trial evidence for testosterone in depth. Mild deficiency is common, particularly in people who sweat heavily on a regular basis.
Signs you may be low: a blunted sense of taste or smell, slow-healing cuts, and catching colds more often than usual are the common markers of mild zinc deficiency.
Dose: 15–30 mg/day, bisglycinate form for absorption.
Long-term use: add 1–2 mg of copper to prevent zinc-induced copper depletion, and don't exceed 40 mg/day without guidance.
Ashwagandha (KSM-66)
A randomised, double-blind, placebo-controlled trial of a standardised high-concentration ashwagandha root extract found substantial reductions in stress and anxiety scores over 60 days compared to placebo, alongside a meaningful reduction in serum cortisol (the stress hormone, measured in the blood)[6] — one of the more rigorously conducted trials behind any adaptogen marketed for stress specifically. Cortisol regulation itself is stress physiology, covered in more depth in the Stress, Breathing & the Nervous System guide.
Dose: 300–600 mg/day of a standardised extract like KSM-66.
Cautions: can cause gastrointestinal upset; rare liver injury reports exist; may interact with thyroid medication and sedatives. Cycling 2–3 months on, 1 month off is a reasonable, conservative approach given the still-developing long-term safety picture.
Section takeaway
Zinc addresses a genuine, common cofactor gap with modest supplementation. Ashwagandha has one of the better-conducted individual trials behind any adaptogen — a real result, though still a single-study evidence base rather than the depth behind creatine or vitamin D.