What it's actually good for
Zinc is an essential trace mineral your body can't store in any meaningful reserve — you need a steady supply from food or supplements to keep immune cells, enzymes, and DNA synthesis running. Most people eating a varied diet, especially one with meat or shellfish, get enough. The people who don't: vegetarians and vegans (plant phytates bind zinc and block absorption), pregnant and breastfeeding women, older adults, people with IBD or celiac disease or a history of bariatric surgery, and people with alcohol use disorder, per the NIH Office of Dietary Supplements. For everyone else, the strongest supplementation case isn't daily insurance — it's short-course use at the first sign of a cold.
What the research says
Immune support and colds (Grade B). A 2013 Cochrane review by Singh and Das, covering 18 RCTs, found that zinc lozenges or syrup started within 24 hours of symptom onset shortened cold duration by roughly a day. That's a treatment effect, not a prevention effect — there's less consistent evidence that daily zinc keeps you from catching a cold in the first place. The review also flagged real heterogeneity in dose, formulation (acetate vs. gluconate), and duration across trials, which is why this lands at Grade B rather than A: the direction of effect is solid, the optimal protocol is still fuzzy.
Testosterone — mostly a myth for non-deficient men. Zinc is required for testosterone synthesis, and correcting a genuine deficiency reliably raises low testosterone back toward normal. But in men who already have adequate zinc status, supplementing on top of that doesn't push testosterone higher. The "zinc boosts T" claim popular in supplement marketing conflates deficiency correction with enhancement — real for the former, unsupported for the latter.
Wound healing — biologically plausible, clinically inconsistent. Zinc is genuinely required for collagen synthesis and tissue repair, and deficiency slows healing. But trials testing oral zinc supplements specifically for wound healing (leg ulcers, pressure ulcers) in people who aren't deficient have produced mixed, mostly null results, hampered by small and lower-quality studies. Zinc belongs in the wound-healing story mechanistically; it's not a proven stand-alone treatment.
How much, and which form
The RDA is 11 mg/day for men and 8 mg/day for women. For general support, 15-30 mg/day of a well-absorbed form covers most people. For colds specifically, the studied lozenge protocol uses 75+ mg/day of ionic zinc (acetate or gluconate lozenges, not swallowed capsules), started within the first day of symptoms and continued only for the illness — not as a standing daily habit.
Form matters: zinc picolinate, citrate, and gluconate absorb well; zinc oxide, cheap and common in low-end multivitamins, doesn't. Vegetarians and vegans can improve absorption from food by soaking beans and grains before cooking, per NIH guidance.
Safety & interactions
Zinc is well-tolerated within the 40 mg/day upper limit for adults. Nausea on an empty stomach is the most common complaint. Sustained intake above 50 mg/day is where problems start: interference with copper absorption (leading to copper deficiency with prolonged use), reduced immune function — ironic, given the reason most people take it — and lower HDL cholesterol. Zinc can also blunt absorption of quinolone and tetracycline antibiotics and of penicillamine, so separate dosing by a couple of hours; high-dose iron and zinc compete for absorption when taken together. This is informational, not medical advice — check with a clinician before starting, especially if pregnant, nursing, or on medication.
How we picked the brand
A zinc product earns a spot when it uses a well-absorbed form (picolinate, citrate, or gluconate — not oxide), states elemental zinc dosage clearly, passes independent third-party testing, and skips unnecessary fillers. Thorne's zinc picolinate is NSF Certified for Sport and meets all four.