What can a nutritional therapist legally claim in the UK?
The ASA keeps a standing advice page for nutritional therapy, which tells you how often this comes up. It is short, and most of the trouble practitioners get into is covered on it. Here is what it says, in the order it matters, with the rule numbers so you can check anything yourself.
- You can say nutritional therapy supports general health and wellbeing, helps with weight management, and helps build a diet for an active life.
- You cannot say it treats or prevents disease without robust clinical evidence.
- Detox claims are treated as unevidenced by default.
- "Dietitian" and "dietician" are protected titles. Do not imply you hold one.
- The ASA names seven conditions where a treatment claim risks discouraging medical care, and says the list is not exhaustive.
The ASA's own page lists claims it considers likely to be acceptable. These are the safe ground, and they are broader than many practitioners assume:
- That nutritional therapy can have a positive overall effect on health and wellbeing.
- That it can help someone manage their weight.
- That it can help devise a diet suited to an active or sporting life.
Read the shape of those rather than only the words. Each one is about supporting a person, with no disease named and no mechanism claimed. Copy that stays in that shape rarely causes a problem.
| Claim | Why it is a problem | Rule |
|---|---|---|
| Treats or prevents a disease or medical condition | The ASA and CAP say they have not seen evidence for it. Needs robust clinical evidence | 12.1 |
| Detoxification, removing toxins, clearing waste | Treated as unevidenced. The liver and kidneys already do this, and no evidence shows diet changes beyond a healthy balanced diet add to it | 12.1 |
| Increases cellular energy | Upheld against in 2011 because the advertiser could not substantiate it | 12.1 |
| Treating a condition that needs medical supervision | Risks discouraging essential treatment | 12.2 |
| Implying a balanced diet cannot supply what someone needs | Not allowed for food supplements | Section 15 |
| Implying a widespread vitamin or mineral deficiency | Needs well-established proof | 15.8 |
The conditions the ASA names by default under rule 12.2 are anaemia, diabetes, high blood pressure, infertility, gastric ulcers, metabolic disease and obesity. It states plainly that the list is not exhaustive, so do not read it as the boundary.
Obesity being on that list catches people out. Weight management is explicitly fine. Treating obesity is not. The difference is whether you have named a medical condition and offered to treat it.
The ASA is explicit that nutritional therapists must not confuse consumers with dietitians registered with the Health and Care Professions Council. "Dietitian" and "dietician" are protected terms. "Nutritionist" is not protected in the same way, which is a frequent source of confusion in both directions.
- Name your actual qualification and your registering body
- Say what your training covers
- Link to your register entry where there is one
- Use "dietitian" or "dietician" about yourself unless you are registered
- Use clinical-sounding framing that implies a protected role
- Imply NHS association where there is none
- 1Does it name a disease or medical condition? If yes, you need robust clinical evidence or the sentence goes.
- 2Does it promise a physiological mechanism — detox, cleanse, boost, restore? If yes, it needs substantiation you probably do not have.
- 3Could a reader delay seeing a doctor because of it? If yes, rewrite regardless of your evidence.
- 4Does it imply a qualification you do not hold? If yes, rewrite.
- 5Is it about supporting a person rather than curing a thing? If yes, you are most likely fine.
The CAP guidance note on health, beauty and slimming claims sets out what level of evidence is expected. It is worth reading once properly rather than guessing per sentence, because the standard is higher than most practitioners expect.
The practical squeeze is that you cannot claim outcomes, but you still have to show prospective clients that working with you does something. The way out is the same one used in every other regulated category: describe what you measure rather than what you cure.
A client's own sleep, resting heart rate and activity over several months are their data, measured by a device they already own. Showing that something moved, for that person, over that period, is a statement of fact about one person rather than a claim about what nutritional therapy treats. That distinction is the whole game.
Does this apply to my website or only to paid ads?
The CAP Code covers non-broadcast marketing including your own website pages that market your services, not only paid placements.
Is the ASA page binding?
It is CAP Executive guidance and says on its face that it does not bind the ASA or CAP. It is still the clearest statement of how these claims get treated in practice.
Can I describe a client case study?
Testimonials do not substantiate a claim. A case study that amounts to a treatment claim is treated as a treatment claim regardless of whose words it is in.
What if my professional body says something different?
Your registering body sets your professional standards and the ASA governs your advertising. You have to satisfy both, and the stricter one applies.