1. Foods, supplements and medicines
UK law divides these products by what they are presented as and what they do. A medicinal product is one presented as having properties for treating or preventing disease, or one that acts pharmacologically to restore or modify physiological function. Medicines require a licence, and a licence requires evidence of quality, safety and efficacy submitted to the MHRA.
A food supplement is a concentrated source of nutrients or other substances with a nutritional or physiological effect, sold in dose form. It is regulated as a food. Food law imposes obligations about safety, composition, labelling and claims. It does not require a manufacturer to demonstrate that the product produces the benefit the buyer expects.
The line between the two is drawn on presentation and function, which is why supplement marketing is written the way it is. Say too plainly that a product treats a condition and it becomes an unlicensed medicine, with legal consequences. This is the single most useful thing to understand about supplement copy: the careful phrasing is not timidity, it is compliance.
2. There is no pre-market efficacy test
Consumers routinely assume that a product on a UK shelf has been assessed by somebody and found to work. For supplements, that assumption is wrong. No regulator reviews trial data on a food supplement to decide whether it does anything before it is permitted to be sold.
What does exist is a claims regime. Health claims made on foods and supplements must come from an authorised list, and getting a claim authorised does require evidence assessed by scientific experts. The list is short relative to the volume of products on sale, and it is heavily populated by claims about established nutrients: contributions to normal immune function, normal collagen formation, the maintenance of normal skin, and similar.
Note the wording of those permitted claims. They are about contributing to normal function, which is a statement about physiology in general, not a promise of improvement in you specifically. Vitamin C contributes to normal collagen formation is true of everyone with adequate vitamin C, and it does not imply that taking more will improve your skin. The claim regime constrains what can be said and does not stop the reader inferring more than was said. That inference is where most of the marketing value sits.
3. Reading a supplement label properly
- The permitted claim. Usually a phrase built around contributes to, supports or helps maintain normal something. Treat it as a statement about nutritional physiology rather than about outcomes.
- The structural language around it. Words that imply benefit without making a claim: designed for, formulated to support, inspired by, works with your body. These have no defined meaning.
- The reference intake percentage. Useful, because it shows whether a dose is a sensible nutritional top-up or a large multiple of what anyone needs.
- The actual quantity of the interesting ingredient. Proprietary blends that list a combined total for several ingredients conceal how little of each is present.
- The form. For minerals in particular, the salt used affects absorption and tolerability, and it is disclosed on the ingredient list rather than the front of the pack.
4. Cosmetics are a separate regime again
Topical products sit under cosmetics law rather than food law. A cosmetic product must be safe for its intended use, must have a safety assessment on file, must have a responsible person in the UK, and must be notified before it is placed on the market. Certain ingredients are prohibited or restricted, and ultraviolet filters are permitted only from a defined list at defined maximum concentrations.
Again, this is a safety regime rather than an efficacy regime. A cosmetic can be sold without demonstrating that it produces the appearance change implied by its marketing. Claims about cosmetic products are separately governed by advertising rules, which is why the Advertising Standards Authority is a more common route of challenge than the product regulator.
Where a topical product does make a genuine therapeutic claim, or contains an ingredient at a level with a pharmacological action, it crosses into being a medicine and requires a licence. This is the line prescription strength retinoids sit on the other side of.
5. What protection does exist
The picture is not lawless, and it is worth being fair about what is in place. Supplements sold in the UK must be safe. Manufacturers carry legal responsibility for the safety of what they place on the market. Certain substances are prohibited or restricted. Labelling requirements apply. Trading standards can act on unsafe or misdescribed products. The MHRA acts where a product is effectively an unlicensed medicine and publishes warnings about dangerous products. The Advertising Standards Authority rules on misleading claims. And the Yellow Card scheme accepts reports of suspected adverse reactions to herbal and complementary products.
What none of that amounts to is a check that the product works.
6. Buying from outside the regulated market
The protections described above attach to products placed on the UK market by a responsible business. Products bought directly from overseas sellers through online marketplaces may sit outside them entirely.
Documented problems in that space include undeclared pharmaceutical ingredients, heavy metal contamination, doses that do not match the label, and prescription-only medicines sold without any prescription. A product that arrives in a jiffy bag from an unidentifiable seller has no responsible person, no safety file you could ever see and no route to complain. Price is rarely the saving it appears to be.
7. What this means for a reader
Assume nothing has been verified about whether a supplement works. Read the permitted claim as a statement about normal physiology rather than a promise. Check quantities against reference intakes. Buy from regulated UK retailers and pharmacies. Tell your GP and pharmacist what you take. And when a product implies a benefit without stating one, notice that the phrasing was chosen by somebody who knew exactly what they were not allowed to say.
For how we assess the evidence behind these products regardless of what the label is permitted to claim, see how we grade evidence.