Supplements and medicines: where the line runs

Published: 2 July 2026 · Updated: 18 August 2026

This distinction is not a formality. It determines what a product may promise, who may sell it and what "works" means in each case.

A medicine: the burden of proof sits with the manufacturer

Before reaching the market a medicine goes through clinical trials that must prove two things: that it works on a specific condition and that its benefit outweighs its risks. Only then is it registered and allowed to say "treats".

A supplement: the food category

A food supplement legally belongs to the food category, not the medicine one. Its task is to complement the diet. It does not go through clinical trials on a specific disease and therefore has no right to claim that it treats one.

That does not make a supplement useless. It means its role is different: filling a magnesium or vitamin D shortfall is a real, measurable task.

Which wordings are permitted

European regulation maintains a list of approved health wordings. For example: "magnesium contributes to normal muscle function" or "zinc contributes to the maintenance of normal testosterone levels in the blood".

Notice the word "normal". These wordings concern supporting normal function, not restoring a disturbed one. That is exactly the line dishonest advertising crosses.

Practical conclusions for a buyer

If a product promises to cure a disease, then either it is a medicine (and needs a prescription and a doctor), or it is lying.

• "Treats", "cures", "eliminates" — those words on a supplement page break the law
• "Contributes to", "complements the diet", "traditionally used" — those are correct wordings
• Specific kilograms, percentages and deadlines in supplement advertising are a warning sign
• Replacing a prescribed medicine with a supplement — never

How evidence is read

When a product description talks about research, the first question is who the research was carried out on. A result obtained in a test tube (in vitro) says nothing yet about a human being; an experiment in animals is one step closer, but still not the last one. Research in people, in turn, varies by the number of participants and by whether there was a control group.

The second question is what was compared with what. If nobody was set against the group that took the product, a change may simply be attributed to time, to the season or to some other change of routine. That is exactly why a randomised trial with a placebo group counts as the gold standard.

What a permitted wording looks like in practice

Correct text on a supplement usually sounds like this: "contributes to normal function", "takes part in metabolism", "nutritional support". These phrases describe the role of a substance in the normal working of the body, not an effect on a disease.

Forbidden wording is anything that promises a medical outcome: "treats", "restores a damaged organ", "replaces a doctor’s prescription". If you read such words on a pack or in an advert, it points to one of two things: either the product is being sold in bad faith, or the text was written without anyone reading the law.

Who answers for a product on the market

For a medicine, the chain of responsibility is strictly formalised: manufacturer, registration dossier, importer, pharmacy. For a food supplement that chain is shorter and looser — which is exactly why who you obtain the product from matters more.

The practical conclusion for a buyer: the more transparent the source — an official channel, an authorised representative or a pharmacy chain — the fewer points exist at which a product can be stored wrongly, repackaged or substituted. That is not a guarantee of quality, but it reduces risk.