In 1747, when the Scottish ship's doctor James Lind documented the first clinical trial against scurvy at sea and identified citrus fruits as life-saving, it marked a turning point in medicine. Less known is the groundbreaking work of biochemist Szent-Györgyi, which was later popularized by women like nutritionist Mary Swartz Rose, who shaped dietary standards in public health – thereby bringing vitamin C into practice. Today, in a world of constant performance, alongside vitamin C, a second, quieter player comes into focus: zinc. Together, they form a duo that sharpens our immune system – subtly but effectively.

Zinc is an essential trace element, a tiny nutrient with a significant impact: it regulates hundreds of enzymes and controls cell division and immune response. Vitamin C, chemically ascorbic acidwater-soluble antioxidant, stabilizes immune defense, protects cells from oxidative stress, and supports the function of leukocyteswhite blood cells, central immune cells. Both nutrients are particularly relevant for innate immunityimmediate defense such as phagocytes and natural killer cells and adaptive immunitytargeted defense by T and B cells. Practically, this means that zinc helps immune cells to efficiently recognize and respond, while vitamin C keeps the cells functional and protects them in the "fire" of inflammation. Since the body does not store vitamin C and zinc levels fluctuate due to diet, exercise stress, or infections, a functional deficiency can easily occur in winter or under high stress – with noticeable effects on energy, recovery, and resilience.

The evidence shows that adequate zinc lowers susceptibility to infections and supports a robust immune response. In population-based data, zinc supplementation reduced the incidence of respiratory infections such as pneumonia and diarrheal diseases – a strong signal of the importance of zinc in infection resistance ^[1]. Vitamin C, in turn, shortens the duration and severity of colds with regular intake; under high physical stress, it even halved the cold rate in studies ^[2]. Both nutrients stabilize central immune functions – from the activity of natural killer cells to chemotaxis – and can thus reduce the risk, severity, and duration of infections, especially in stressed or older populations ^[3]. At the same time, too much of a good thing can backfire. Excessive zinc can disrupt copper metabolism and lead to hematological and neurological problems ^[4], and very high doses of vitamin C increase oxalate excretion, thereby raising the risk of kidney stones ^[5][6].

Several controlled studies present a consistent picture with practical relevance. Research on zinc shows that supplementation in deficient or stressed groups reduces the frequency of infections such as diarrhea and pneumonia and shortens disease courses – an indication that adequate zinc supply can strengthen immune resilience, especially during periods of high exposure or in winter months ^[1]. For vitamin C, systematic evaluations of controlled studies show that in the general population, a daily high dose does not reliably prevent colds, but reduces severity and duration; in athletes and individuals under significant physical stress, vitamin C halves the incidence of colds – presumably because infection stress and oxidative pressure deplete vitamin C reserves more quickly ^[2]. Mechanistically plausible, this is supported by findings that vitamin C and zinc modulate key processes of innate defense – from oxidative burst to NK cell activity – thus improving early control of pathogens ^[3]. Concurrently, case and intervention data call for careful dosing: chronically high zinc levels can induce copper deficiency, sometimes associated with anemia and neurological symptoms ^[4], and high doses of vitamin C significantly increase oxalate excretion, which raises the risk of calcium oxalate stones ^[6][5]. The essence is to supplement purposefully and moderately – particularly as needed, not indiscriminately.

- Assess your needs: During the cold season or under high stress, a moderate zinc supplement may be beneficial. Refer to common daily amounts and consult your doctor if planning long-term intake to clarify copper status and needs ^[1].
- Timing for vitamin C: In phases of intense training or high infection exposure, regular vitamin C can help mitigate colds; during acute symptoms, some individuals consider higher doses for a short period to shorten the duration – always with an eye on individual tolerance and kidney stone risk ^[2][3].
- Careful dosing: Avoid excessive zinc amounts to prevent copper deficiency, especially with long-term use or “cold experiments” ^[4].
- Keep kidneys in mind: If you are prone to kidney stones, avoid very high doses of vitamin C; excessive intake increases oxalate excretion and thus the risk of stones ^[5][6].
- Kitchen as a laboratory: Cook gently. Steaming or brief microwaving reduces vitamin C losses compared to prolonged boiling; avoid excessive heat and large amounts of water to preserve the content in vegetables ^[7].

Zinc and vitamin C are not miracle cures, but when used wisely, they are strong allies for a resilient immune system. Focus on need-based dosing, short, targeted phases, and gentle cooking. Start this week: plan your shopping, adjust preparation methods, and review your supplement plan – for more energy, robustness, and high performance.