Zinc
Essential mineral: deficiency directly suppresses testosterone production.
What is Zinc?
Zinc is an essential trace mineral involved in over 300 enzymatic reactions in the body. It is critical for testosterone synthesis, sperm production, immune function, and wound healing. The UK population is frequently deficient, particularly men who sweat heavily, drink alcohol regularly, or eat a low-meat diet.
What does the evidence say?
A landmark 1996 study by Prasad et al. found that zinc supplementation in zinc-deficient elderly men nearly doubled testosterone levels over six months. Research by Kilic et al. (2010) showed that zinc supplementation prevented the exercise-induced decrease in testosterone in wrestlers. A 2010 Cochrane-style review confirmed zinc's role in male reproductive health. The key caveat: these benefits are most pronounced in those who are deficient: if you're already replete, additional zinc may not raise testosterone further.
Multiple high-quality randomised controlled trials with consistent results and independent replication.
Dosage guide
| Effective dose | 25–45mg elemental zinc per day |
| Maximum dose | 40mg per day from supplements (UL set by NHS and EFSA) |
| Timing | With food to reduce nausea. Avoid taking with iron or calcium supplements as they compete for absorption. |
Best form to buy
Zinc bisglycinate or zinc picolinate for best absorption. Avoid zinc oxide: it has poor bioavailability and is the cheap form used in most multivitamins.
Who benefits most
Men who train heavily (zinc is lost in sweat), men who drink alcohol regularly, vegetarians and vegans, and anyone who has not had their zinc status checked recently.
Side effects and safety
Nausea if taken on an empty stomach. Long-term high-dose supplementation (above 40mg/day) can deplete copper: consider a zinc-copper ratio supplement or monitor intake. High doses can also suppress immune function, which is the opposite of the intended effect.
“Get your zinc tested before supplementing. If you're deficient, fixing it could genuinely shift your testosterone. If you're not deficient, extra zinc won't help much. Bisglycinate is the form worth paying for.”