Think you eat only healthy, unprocessed foods? Think again. Joanna Blythman went undercover and discovered that even your fruit salad is not what it seems.

Manufactured foods often contain chemicals with known toxic properties – although, again, we are reassured that, at low levels, this is not a cause for concern. This comforting conclusion is the foundation of modern toxicology, and is drawn from the 16th-century Swiss physician, Paracelsus, whose theory “the dose makes the poison” (ie, a small amount of a poison does you no harm) is still the dogma of contemporary chemical testing. But when Paracelsus sat down to eat, his diet wasn’t composed of takeaways and supermarket reheats; he didn’t quench his thirst with canned soft drinks. Nor was he exposed to synthetic chemicals as we are now, in traffic fumes, in pesticides, in furnishings and much more. Real world levels of exposure to toxic chemicals are not what they were during the Renaissance. The processed food industry has an ignoble history of actively defending its use of controversial ingredients long after well-documented, subsequently validated, suspicions have been aired.

The precautionary principle doesn’t seem to figure prominently in the industry’s calculations, nor – such is their lobbying power – does it loom large in the deliberations of food regulators. If it did, then steering clear of manufactured products would be a lot easier.

The pace of food engineering innovation means that more complex creations with ever more opaque modes of production are streaming on to the market every day. Just last month, a dossier for a new line of dairy proteins dropped into my mailbox. Alongside a photo of a rustic-looking, golden pan loaf, the explanation read: “Many bakers are now turning to permeates, a rather new ingredient in the food ingredients market. Permeate is a co-product of the production of whey protein concentrate (WPC), whey protein isolate (WPI), ultrafiltered milk, milk protein concentrate (MPC), or milk protein isolate (MPI).”

Permeate, apparently, “contributes to the browning of baked goods” and produces bread that “retains its softness for a longer period of time and extends shelf life”. How clever. But I would prefer that my bread was browned solely from the application of heat. I’m prepared to accept that it will stale over time, rather than eat something that owes its existence to ingredients and technologies to which I am not privy, cannot interrogate and so can never truly understand. Am I about to hand over all control of bread, or anything else I eat, to the chemical industry’s food engineers? Not without a fight.

What your food label really means

Added vitamins One-dimensional factory versions of natural vitamins found in whole foods: ascorbic acid (man-made vitamin C) is usually synthesised from the fermentation of GM corn, while artificial vitamin E is commonly derived from petrol.

Soluble fibre A healthier-sounding term for modified starch, which is widely used to reduce the quantity of more nutritious ingredients in processed foods, and keep down manufacturers’ costs.

‘Natural’ colourings The only difference between these and artificial ones is that they start with pigments that occur in nature. Otherwise, they are made using the same highly chemical industrial processes, including extraction using harsh solvents.

Artificial ‘diet” sweeteners Several large-scale studies have found a correlation between artificial sweetener consumption and weight gain. Accumulating evidence suggests that they may also increase our risk of Type 2 diabetes.

Enzymes Used to make bread stay soft longer; injected into low-value livestock before slaughter, to tenderise their meat; and used in fruit juice processing to create a cloudier, more natural appearance.

‘Packaged in a protective atmosphere’ Food that has been “gassed” in modified air to extend its shelf life. It delays what food manufacturers call “warmed over flavour”, an off-taste that occurs in factory food.

Beef/pork/poultry protein Collagen extracted from butchered carcasses, processed into a powder and added to low-grade meats. It adds bounce, increases the protein content on the nutrition label and, combined with water, is a substitute for meat.

Washed and ready-to-eat salads “Cleaned” by sloshing around in tap water dosed with chlorine, often with powdered or liquid fruit acids to inhibit bacterial growth. The same tank of treated water is often used for 8 hours at a time.

‘Pure’ vegetable oil Industrially refined, bleached, deodorised oils. Food processors often add chemicals to extend their “fry life”.

‘Natural’ flavourings Even the flavour industry concedes that “there isn’t much difference in the chemical compositions of natural and artificial flavourings”. They are made using the same physical, enzymatic, and microbiological processes.