Zinc in Endurance Sports: Deficiency, Dosage, Immunity

Zinc is the trace element endurance athletes talk about least — and the one quietly involved in every second performance factor. It drives immune defence after a long run, sits in countless enzymes of energy metabolism and shapes hormone status. If you sweat a lot and eat a plant-based diet, you slip into a silent deficiency faster than you would like.

Why zinc matters in endurance sport

Zinc takes part in more than 300 enzymatic reactions in the body, and a good share of them relate to training adaptation. It is a cofactor of superoxide dismutase, one of the body's key antioxidants that buffers the cell damage from high oxygen turnover. It feeds into carbohydrate and fat metabolism, into protein synthesis after exercise and into wound healing — precisely the processes running non-stop during hard training blocks.

The second major area is immune function. Zinc is essential for the maturation and function of T cells. That explains the well-known link between hard endurance work and increased susceptibility to infection: in the hours after long, intense sessions a brief immune window opens in which the body is more vulnerable. If a zinc deficiency runs in parallel, that window widens. The details are in the article on the immune system and endurance training.

Third, zinc acts on the hormonal axis. It is relevant for testosterone production, which matters equally for men and women when it comes to recovery, muscle building and drive.

How much zinc do you actually need?

The official intake recommendations are modest. The German Nutrition Society cites around 11 mg per day for men and 8 mg for women; the EFSA is similar at 9.4 mg and 7.5 mg. Those are values for adults without special demands — the lower bound, not the target for an ambitious endurance athlete.

In practice a range of 10 to 15 mg per day from normal food is sensible, trending towards the upper end in phases of heavy sweating, on a vegetarian or vegan diet and during race preparation. Upwards, the room is clearly limited: the EU upper limit for daily intake is 25 mg. More than 40 mg per day over the long term disrupts copper absorption and can, via copper deficiency, achieve the exact opposite — a weakened immune defence, changes in the blood count and neurological symptoms.

The best zinc sources — and their hidden problem

Zinc is widely distributed in food, but the quality of sources varies sharply. Animal foods deliver zinc in a form the body absorbs well: oysters are by far the strongest source at over 20 mg per 100 grams, followed by beef (around 5 to 6 mg per 100 g), lamb, cheese, offal and eggs. Roughly 30 to 40 percent of the zinc from these sources actually reaches the body.

Plant sources are rich too — pumpkin seeds, sesame, cashews, oats, pulses and wholegrains all carry relevant amounts. The problem is bioavailability: phytates, the phosphorus storage form in grains and pulses, bind zinc in the gut and cut absorption to about 15 to 20 percent. If you eat vegetarian or vegan, you therefore need roughly 50 percent more zinc than the general recommendation to reach the same absorbed amount.

There are simple levers against this:

• Soak and sprout. Even several hours of soaking measurably lowers the phytate content of pulses and grains. Sprouting works even better.
• Sourdough instead of yeast. Fermentation in sourdough breaks down phytates through the microorganisms — sourdough bread delivers clearly more available zinc than yeast bread.
• Pair with vitamin C. A portion of pepper, lemon or berries with a pulse-based meal raises zinc uptake. The article on vitamin C in endurance sport uses the same effect.
• Mix animal and plant foods. Even a small amount of meat, fish or egg in the pulse stew improves absorption of all the plant zinc.

For orientation: 30 grams of pumpkin seeds provide about 2.2 mg of zinc, 100 grams of oats around 3 mg, 100 grams of beef 5 to 6 mg. A normal mixed diet reaches the 10 to 15 mg without tricks — a vegan day with plenty of wholegrains and pulses gets there on paper too, but in practice only with deliberate choices.

Losses through sweat

Sweat is not pure salt water. Alongside sodium, potassium and magnesium, trace elements are lost through the sweat glands, zinc among them. Estimates run at 0.5 to 1.0 mg of zinc per litre of sweat, and higher at very high sweat rates and temperatures. If you put in 8 to 10 training hours in a hard summer week with a litre of sweat loss each, you lose roughly 5 to 10 mg of zinc through sweat — half the daily intake.

On its own that rarely causes a deficiency with good nutrition, because the body can counter-regulate through intestinal excretion: it adapts the absorption rate to demand. It becomes critical only when several factors coincide — high sweat losses, additional phytate from a plant-based diet, heavy sweating in hot periods and a training camp with three sessions a day. The role of electrolytes in this is covered in the article on electrolytes when running.

How to recognise a deficiency

A developing zinc deficiency is tricky because the symptoms are non-specific and arrive slowly. Typical signs are increased susceptibility to infection with frequent colds, small wounds healing more slowly, a reduced sense of smell and taste, brittle nails, hair loss, impaired wound healing and a general fatigue that extra sleep does not fix. In severe cases skin changes appear and, if it persists, a disrupted hormone status. The overlap with overtraining symptoms is considerable — more in the article on recognising overtraining.

Lab diagnostics have a catch: serum zinc is a poor marker, because with a tight supply the body redistributes zinc from the blood into the tissues. An unremarkable serum value therefore does not rule out an early deficiency. More reliable is the combination of zinc in whole blood or erythrocytes, the zinc-to-copper ratio, serum albumin and the symptoms — and that belongs in medical hands, not in self-interpretation.

Zinc and the common cold: what actually helps

Here the evidence is more nuanced than advertising suggests. For treatment there is solid evidence: zinc lozenges or sprays started within 24 hours of the first symptoms and given at a high dose (mostly 75 mg of elemental zinc per day in the studies, short term) shorten the duration of a cold by about a third in meta-analyses. Symptom severity drops too. The effect depends on direct contact of the zinc with the throat lining and on a sufficient amount of zinc reaching the mucosa.

For prevention the evidence is clearly weaker: a daily zinc intake of 15 mg across the winter lowers the risk of a cold only marginally or not at all in most studies. In practice that means zinc as a permanent supplement against colds is overrated, while zinc as an immediate measure at the first symptoms is underrated. Important when taking it: above 40 mg only short term and not on an empty stomach, as it can cause nausea, and not together with magnesium supplements, because the two compete for the same absorption pathways. Anyone already taking magnesium should separate the intake times.

Supplementing: when it makes sense — and when it doesn't

Zinc is one of the nutrients where supplementation only truly helps in defined cases. It makes sense with a medically confirmed deficiency, after prolonged infections or gastrointestinal illness with poor absorption, on a strictly vegan diet with a high phytate load, in a proven high-sweat-loss situation during hot periods and through an intensive race phase with frequent travel. In those cases 10 to 25 mg of elemental zinc per day is a common range.

What does not make sense is permanent high dosing on suspicion. Anyone taking 40 to 50 mg for weeks risks a copper deficiency — and that hits back exactly on the systems you wanted to protect: the immune system and blood formation. Zinc products with added copper are no substitute for a needs-based dose, only a safeguard at medically justified higher intakes.

On the form: zinc gluconate and zinc sulfate are both well absorbed; zinc citrate and zinc picolinate are considered slightly better tolerated, especially on an empty stomach. It is important not to combine several zinc-containing products and not to take it with high-dose iron or calcium, because these minerals compete for the same transport pathways. Anyone supplementing iron should read the article on iron deficiency in endurance athletes and separate the intake times.

The five most common mistakes

• High dosing on suspicion. Without a measurement the dose is guesswork — and too much zinc harms the copper balance more than too little zinc helps in most cases.
• Ignoring phytates. Anyone eating plenty of wholegrains and pulses without soaking, sprouting or sourdough loses a large part of the zinc they take in before it reaches the body.
• Combining zinc with magnesium or iron. All three compete for the same absorption pathways. Separating intake times solves the problem in one move.
• Reading the deficiency off the serum value. A normal serum zinc does not rule out an early deficiency. Symptoms, the zinc-to-copper ratio and whole-blood values belong in the diagnosis.
• Zinc as a substitute for recovery. No supplement compensates for too little sleep, too steep a load increase or a persistently deep TSB. Zinc is a building block, not a miracle cure.

How zinc fits into training planning

Peakora assesses micronutrients not in isolation but in the context of load. Anyone training for weeks in a very deep TSB range — that is, with a negative form curve and high acute fatigue — has an elevated risk for the immune window and benefits most from deliberate nutrition. Peakora makes that phase visible: the 24-hour recovery monitor shows form (TSB), sleep and rest from training in separate components, so you can see when the immune system needs support rather than more sessions. The basics are in the Peakora glossary, and anyone wanting to plan nutrition around training will find the framework in the article on nutrition after training.

Concretely for practice: in weeks with hard key sessions and long runs, focus on a zinc-rich base diet — beef, cheese, eggs, pumpkin seeds, oats. In hot periods and training camps, cover sweat losses through electrolyte drinks instead of one-sidedly supplementing zinc. And with frequent infections over several weeks, do not add to the dose but review the load and get a medical assessment.

Frequently asked questions about zinc in endurance sport