Zinc for Athletes: What the Evidence Shows
Zinc is a staple of "testosterone booster" labels and immune-support formulas, and many athletes take it almost by default. Our editorial team looked at the research to answer a simpler question: when does zinc actually help a physically active person, and when is it just an expensive habit or even a risk?
Zinc's job in the body
Zinc is an essential trace mineral, meaning the body cannot make it and has no large dedicated storage pool. It is a structural or catalytic component of hundreds of enzymes and of so-called zinc-finger proteins that regulate gene expression. Practically every tissue depends on it.
For athletes, the most relevant functions include protein synthesis and tissue repair, immune cell development, antioxidant defense through superoxide dismutase, carbohydrate metabolism, and the production and signaling of several hormones, including testosterone, insulin and thyroid hormones.
About 60% of the body's zinc is located in skeletal muscle and roughly 30% in bone. Blood contains only a small fraction, which is why serum zinc is an imperfect marker. Levels drop temporarily with inflammation, after meals and following intense exercise, and may not reflect total body status.
The US Recommended Dietary Allowance set by the National Academies is 11 mg per day for adult men and 8 mg for adult women, with higher values during pregnancy and lactation. The Tolerable Upper Intake Level for adults is 40 mg per day from all sources combined.
Why some athletes run low
Most Americans who eat meat, seafood and dairy meet their zinc needs. However, certain groups of athletes are at higher risk of marginal status, a concern noted in reviews by Lukaski and others.
- Energy-restricted athletes: weight-class sports, aesthetic sports and long cutting phases reduce total intake.
- Vegetarians and vegans: plant foods contain phytates that bind zinc and lower absorption.
- Endurance athletes: zinc is lost in sweat and urine, and heavy training may increase these losses.
- Athletes with gastrointestinal issues: conditions such as celiac disease or chronic diarrhea impair absorption.
Sweat zinc losses vary greatly between individuals and studies, and estimates are uncertain. For most people training an hour a day, they are modest relative to intake. For athletes training several hours daily in heat, they become more meaningful when combined with a restricted diet.
Signs of deficiency are nonspecific: frequent infections, slow wound healing, poor appetite, altered taste and, in more severe cases, hair loss and skin lesions. Low testosterone and reduced performance have been reported in clearly deficient individuals.
| Food | Approximate zinc per serving | Absorption notes |
|---|---|---|
| Oysters (3 oz) | Very high, well above the RDA | Highly bioavailable |
| Beef (3 oz) | About half the RDA for men | Highly bioavailable |
| Pumpkin seeds (1 oz) | About a fifth of the RDA | Phytates reduce uptake |
| Chickpeas (½ cup) | Around a tenth of the RDA | Soaking and sprouting help |
| Fortified cereal | Varies by brand | Check label |
Immunity and upper respiratory infections
Heavy training blocks and competition travel are associated with more frequent upper respiratory infections in some athletes. Zinc is essential for normal function of T cells, natural killer cells and the barrier function of mucosal tissue, as Prasad and others have described.
The strongest clinical evidence for zinc and immunity concerns lozenges used at the first signs of a cold. Meta-analyses by Hemilä suggest that zinc acetate or gluconate lozenges, taken frequently in the first day of symptoms, may shorten the duration of a common cold. The effect seems to depend on zinc being released locally in the throat.
Daily zinc supplementation to prevent colds in well-nourished athletes has weaker support. Correcting a deficiency clearly improves immune function, but adding extra zinc on top of adequate status does not reliably boost it further.
Lozenge regimens used in studies provide high short-term zinc doses, and they should be limited to a few days. Using them continuously can push intake beyond the upper limit and cause side effects.
Testosterone and performance: the honest picture
Zinc is often promoted as a natural testosterone booster. The idea is rooted in real biology: severe zinc deficiency lowers testosterone, and repletion restores it. Small studies from Turkish research groups have also reported that zinc supplementation may blunt the temporary drop in testosterone and thyroid hormones after exhaustive exercise, although these trials were short and involved few participants.
In men with adequate zinc status, however, the picture changes. Koehler and colleagues (2009) gave healthy men a high-dose zinc supplement and found no increase in serum testosterone or in urinary steroid metabolites. Most well-designed studies show the same pattern: zinc fixes a deficit but does not push hormones above normal.
The same principle applies to strength and endurance. There is no consistent evidence that zinc supplementation improves performance in athletes who are not deficient. Popular ZMA formulas (zinc, magnesium and vitamin B6) have shown mixed results, and an independent study by Wilborn and colleagues (2004) failed to reproduce the strength gains reported in an early industry-linked trial.
The practical takeaway is that zinc is a maintenance nutrient, not a performance enhancer. Its value for an athlete lies in preventing the drop in function that comes with inadequate intake.
Supplementing safely
If dietary intake is low or a doctor has confirmed suboptimal status, a supplement providing roughly the RDA, around 8–15 mg of elemental zinc per day, is a reasonable approach. Check the label for elemental zinc, not the weight of the compound.
Common forms include zinc gluconate, citrate, picolinate, bisglycinate and oxide. Oxide is less well absorbed; the others are broadly comparable for practical purposes. Taking zinc with food reduces nausea, but avoid taking it together with high-dose iron or calcium supplements, which compete for absorption.
Chronic intakes above 40 mg per day can cause copper deficiency, which leads to anemia, low white blood cell counts and, in severe cases, neurological damage. Acute high doses cause nausea, vomiting and stomach cramps. Zinc can also reduce absorption of certain antibiotics, such as quinolones and tetracyclines.
Athletes subject to drug testing should prefer products certified by third-party programs, since "testosterone booster" products containing zinc have occasionally been found adulterated with prohibited substances.
Conclusions of the editorial team
Zinc is essential for immunity, tissue repair and hormone production, and athletes with restricted diets or heavy sweat losses can become marginally deficient.
For people with adequate status, extra zinc does not raise testosterone or improve performance. The most useful applications are correcting deficiency and short-term lozenge use at the onset of a cold.
We also suggest reading our articles on magnesium and sleep in athletes, on iron status in female endurance athletes, and on how to read a basic micronutrient blood panel.
References
- Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academies Press; 2001.
- Prasad AS. Zinc in human health: effect of zinc on immune cells. Mol Med. 2008;14(5-6):353–357.
- Lukaski HC. Vitamin and mineral status: effects on physical performance. Nutrition. 2004;20(7-8):632–644.
- Hemilä H. Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open. 2017;8(5):2054270417694291.
- Koehler K, Parr MK, Geyer H, Mester J, Schänzer W. Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement. Eur J Clin Nutr. 2009;63(1):65–70.
- Wilborn CD, Kerksick CM, Campbell BI, et al. Effects of zinc magnesium aspartate (ZMA) supplementation on training adaptations and markers of anabolism and catabolism. J Int Soc Sports Nutr. 2004;1(2):12–20.
