1. The appeal to nature
The appeal to nature is the assumption that because something is natural it is therefore good, or safe, or better than the alternative. It is one of the oldest recognised errors in reasoning and it has become the organising principle of an enormous retail category.
It fails immediately on examples. Deadly nightshade, hemlock, death cap mushrooms, snake venom, arsenic, asbestos and tobacco are all natural. Insulin, paracetamol and the mineral filters in sunscreen are manufactured. Nothing about the origin of a substance predicts what it does in a body.
The word natural also has almost no regulatory meaning in cosmetics and food supplements. A product can be marketed as natural while containing extensively processed extracts, synthesised preservatives and compounds that never existed in the plant named on the front of the pack. The word is doing marketing work, not descriptive work.
2. Dose is what determines harm
The classical formulation is that the dose makes the poison, and it holds. Water is fatal in sufficient quantity. Vitamin A is essential and causes serious toxicity in excess. Oxygen is required for life and damages tissue at high concentrations over time.
Concentration and extraction change dose dramatically, which is where plant products become a genuine concern. Drinking tea is not the same exposure as taking a concentrated tea extract in capsule form, and it never has been. A herb used in cooking for centuries carries a track record at culinary quantities and no track record at all as a standardised extract at many times that intake.
The traditional use argument is worth naming because it is used constantly. Long traditional use is genuinely informative, and what it informs you about is the traditional preparation at the traditional dose. It transfers poorly to a concentrated extract in a capsule, which is a different exposure that no tradition has ever tested.
3. Where real harm has occurred
This is not theoretical, and the general categories are documented in the pharmacovigilance and regulatory literature without needing any specific case invented here.
Liver injury from herbal products. Herbal and dietary supplements are a recognised cause of drug induced liver injury, and specialist liver services see cases. Several concentrated plant extracts sold for weight loss, muscle building and general wellness have been implicated. This is one of the clearest demonstrations that plant origin confers no protection.
Interactions with prescribed medicines. Plant compounds can induce or inhibit the enzymes that metabolise drugs, and can affect clotting. The consequence is that a supplement can reduce the effectiveness of a prescribed medicine or amplify its effect. Patients frequently do not mention supplements to prescribers because they do not consider them medicines. That silence is where the harm happens.
Contamination and adulteration. Products bought from unregulated sources, particularly online from outside the UK, have been found to contain heavy metals, undeclared pharmaceutical ingredients and doses that do not match the label. The MHRA publishes warnings about such products.
Phototoxicity and sensitisation. Several natural essential oils are documented skin sensitisers, and some citrus derived oils cause phototoxic reactions on ultraviolet exposure. Applying an undiluted natural oil to skin before sun exposure is a recognised route to a burn.
4. Plant extracts are not consistent products
A synthesised molecule is the same molecule every time. A plant extract is a mixture whose composition depends on variety, growing conditions, harvest timing, the part of the plant used, extraction method and processing. Two products naming the same plant can differ substantially in what they contain.
This has consequences for both safety and evidence. On safety, a batch can carry more of an active constituent than the last one, and dosing is therefore approximate. On evidence, a study of one standardised extract describes that extract and not the category. Marketing that cites research on one preparation to sell a different one is extremely common and rarely valid. We discuss this at length in polyphenols and photoprotection.
5. Who should be particularly careful
People taking prescribed medicines, particularly anticoagulants, anticonvulsants, immunosuppressants, transplant medicines and treatments with narrow therapeutic windows. People who are pregnant or breastfeeding. People with liver or kidney disease. People awaiting surgery, because some supplements affect bleeding and anaesthesia. People with allergies, since plant products cross react in ways that are not obvious.
The practical rule is short: tell your GP, pharmacist and surgeon everything you take, including the things you do not think count. And report suspected side effects through the MHRA Yellow Card scheme, which covers herbal and complementary products as well as licensed medicines. Under-reporting is why some risks take years to appear.
6. The error also runs the other way
Chemophobia is the mirror image of the appeal to nature: the assumption that synthesised means harmful. It is equally unfounded and it has its own costs. People avoid well tested sunscreen filters in favour of poorly characterised botanical preparations, and end up with less protection against an established cause of skin cancer. People avoid effective prescribed treatment for a skin condition in favour of a natural alternative, and the condition progresses.
Everything is chemicals. The question is never whether a substance is a chemical but what the evidence says about what it does, at what dose, in whom. That question is the whole content of this publication.
7. A workable position
Ask what the evidence shows rather than where the ingredient came from. Prefer defined molecules with known chemistry and human data over undefined mixtures with laboratory data. Buy from regulated UK sources. Assume concentrated extracts are a different exposure from the traditional food. Tell your clinicians what you take. And treat the word natural on packaging as a marketing decision rather than as information.