Zink: Die Wechselwirkung, die seine Wirkung blockiert

Zinc: The Interaction That Blocks Its Effect

Beauty & Skin · approx. 6 min read

Zinc is one of the most unassuming minerals on the supplement shelf – and at the same time, one of the most versatile. It is involved in over 300 enzymes that cells need to divide and renew. This is precisely why a deficiency often first manifests in areas that renew fastest: skin, hair, nails, immune cells. However, the real question is rarely "if", but "how" to take zinc most effectively.

What happens in the body

The body needs zinc for DNA and protein synthesis – in other words, for practically every cell division. Hair follicles, nail beds, and skin cells are among the tissues with the highest renewal rate in the body, which explains why low zinc levels often become noticeable there first: brittle nails, dull hair, skin that heals slower than usual.

Timing: the most underestimated factor with zinc

Here lies the real trick that many overlook: Zinc competes with iron and calcium for absorption in the gut. If you take your zinc supplement together with an iron-containing multivitamin or a glass of milk, the absorption of both substances can inhibit each other. The practical consequence:

  • It is best to take zinc separately from iron supplements – if in doubt, take one in the morning and the other in the evening.
  • Do not combine directly with dairy products if you are taking larger quantities of calcium at the same time.
  • Zinc is best absorbed on an empty stomach – if you are sensitive (slight nausea is possible for some people), take it instead with a small meal that is not too rich in calcium.

Which form makes a difference?

Not all zinc is created equal. Zinc bisglycinate – bound to the amino acid glycine – is considered particularly well-tolerated and tends to be better absorbed than inorganic forms such as zinc sulfate, which are more frequently associated with stomach discomfort. If your supplement has "Bisglycinate" on the label, that's not a marketing term, but a concrete, sensible choice of form.

What supports the effect – and what inhibits it

  • Do not combine with very high-fiber, phytate-rich meals (a lot of whole grains, legumes at once) – phytates bind zinc and measurably reduce absorption. This particularly affects people with a predominantly plant-based diet, who may have a higher zinc requirement anyway.
  • Do not overdose permanently. Unlike many vitamins, zinc has a relatively narrow range between sensible and excessive intake. Permanently very high amounts can interfere with copper absorption. If you are already taking a zinc-containing collagen supplement, add up the total amount from different sources before supplementing with a pure zinc product.
  • Alcohol reduces zinc levels through increased loss via the kidneys – one reason why people with regular alcohol consumption often show low zinc levels.

For men: Testosterone and fertility

Zinc is one of the few micronutrients with its own specifically approved reference to male hormone balance: It contributes to the maintenance of normal testosterone levels in the blood and to normal fertility and reproduction. This does not mean that more zinc automatically means more testosterone – the connection applies to maintaining an already normal level, not as a growth lever beyond that. This becomes particularly relevant in cases of genuinely insufficient supply, for example due to an unbalanced diet, high alcohol consumption, or intense endurance sports with high sweat loss.

For sports and active people

Zinc is measurably lost through sweat, which is why people with intense, regular endurance training may have a higher requirement than less active people. In combination with an already scarcer supply – for example, with a predominantly plant-based diet – this can add up.

What zinc really matters for in everyday life

Zinc's role in immune defense is best researched, especially for existing colds: If sufficient zinc is supplied early – within the first 24 hours after the first symptoms – this was associated with a somewhat shorter cold duration in several studies. A large part of these studies worked with lozenges that release the active ingredient directly in the throat; whether a swallowed capsule achieves the same local effect is less well studied, even if the systemic zinc supply is the same. With already good zinc supply, an additional preventive effect is not reliably demonstrable anyway. For skin, hair, and nails: compensating for an actual deficiency makes a visibly greater difference than additionally boosting an already sufficient supply.

Good to know

Febrile infections or infections lasting longer than a week belong in a doctor's hands – zinc is at most a supplement, never a substitute for treatment.

Relevant products

medi Zinc provides 25 mg of zinc bisglycinate per capsule – the well-tolerated form described in the text.

Sources

  • Zinc for prevention and treatment of the common cold, Cochrane Database of Systematic Reviews (2024). Cochrane Library
  • Zinc Supplementation Reduces Common Cold Duration among Healthy Adults, American Journal of Tropical Medicine and Hygiene 103(1) (2020). ajtmh.org
  • EFSA Scientific Opinion on Dietary Reference Values for zinc (Tolerable Upper Intake Level).
  • EFSA NDA Panel. Scientific Opinion on health claims related to zinc and testosterone, fertility and reproduction (ID 297, 300, 301). efsa.onlinelibrary.wiley.com

This article is for general information purposes only and does not replace individual medical advice.

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