Food Additives: Preservatives, Colours and Flavours, Fairly Assessed

“Chemicals in food” is a poor frame — everything you eat is chemicals. But some additives do carry genuine question marks, and the regulatory picture differs enough between countries to be informative.

Colours

Synthetic food colours are purely cosmetic. They add no flavour, no preservation and no nutrition, which makes the risk-benefit calculation unusual: any risk at all is on one side of the ledger with nothing on the other.

The Southampton study, published in 2007, found that certain colour mixtures were associated with increased hyperactivity in children. The European response was to require products containing them to carry a warning: “may have an adverse effect on activity and attention in children.” Many manufacturers reformulated rather than carry the label — which is why the same brand of sweets is often coloured with paprika and beetroot in Europe and with synthetic dyes in the United States.

The FDA has taken a more conservative view of that evidence. It did, in January 2025, revoke authorisation for FD&C Red No. 3 in food, following the animal carcinogenicity data that had already removed it from cosmetics decades earlier.

Given that colours do nothing except make food look brighter, avoiding them costs you nothing.

Preservatives

Preservatives do real work — preventing spoilage and the genuine food safety risks that come with it. They are not equivalent to colours.

Sodium benzoate is generally regarded as safe, with one specific caveat: in the presence of vitamin C, particularly in acidic drinks and with heat or light, it can form small amounts of benzene. Manufacturers have largely reformulated to avoid this combination.
Nitrites in cured meats can form nitrosamines, which are carcinogenic. This is part of why processed meat is classified as a Group 1 carcinogen by IARC. Note that “uncured” products preserved with celery powder contain naturally occurring nitrates and are not meaningfully different — the labelling is a regulatory artefact.
BHA and BHT are antioxidant preservatives with mixed animal data. BHA is listed as reasonably anticipated to be a human carcinogen by the US National Toxicology Program at high doses. Both remain permitted at low levels.
Sulphites are safe for most people and trigger genuine reactions in a minority, particularly some asthmatics. They must be declared for that reason.

Where regulators disagree

Two examples worth knowing, because they show the judgements involved are not purely scientific.

Titanium dioxide (E171), a whitening agent, was banned as a food additive in the EU in 2022 after its safety panel concluded genotoxicity could not be ruled out. It remains permitted in the United States.

Potassium bromate, a flour treatment, is banned in the EU, UK, Canada and elsewhere, and still permitted federally in the US.

Different regulators reading similar evidence reach different conclusions, largely because they apply different precautionary standards. Neither position is unscientific; they weigh uncertainty differently.

Emulsifiers, the newer question

Emulsifiers such as polysorbate 80 and carboxymethylcellulose keep processed foods stable. Animal work has shown effects on the gut mucus layer and microbiome, and early human data points in a similar direction. This is an active area rather than a settled one, and it is one of the more plausible mechanisms by which processed food might affect health beyond its calorie content.

The finding that matters most

Here is the part that gets lost in additive-by-additive argument. The strongest signal in the research is not about any individual additive. It is that ultra-processed food as a category is associated with worse health outcomes — weight gain, cardiovascular disease, type 2 diabetes, mortality — across large cohorts and in at least one well-controlled feeding trial.

Whether that is caused by the additives, by the energy density, by how quickly such food is eaten, by what it displaces, or by all of these together is not resolved.

Which points at a more useful heuristic than memorising E numbers: a long additive list is a reliable marker that you are holding ultra-processed food. That is the signal worth acting on, and it does not require you to adjudicate the toxicology of any single ingredient.

A sane approach

Avoid synthetic colours, which do nothing for you. Treat processed meat as an occasional food. Do not agonise over a preservative in an otherwise decent product. And spend your attention on the overall composition of what you eat rather than on individual ingredient names — that is where the evidence actually points.