The tale of the snail and hare. Why science is catching up with the Slow Food message. Part 2: all about additives.

Every day, we consume food additives and preservatives. They keep our food safe, and create new textures and products that would not otherwise exist in nature.

Some of these – salt or the acid or vinegar to preserve food, an egg yolk as emulsifier for mayonnaise – have existed for millennia. But it is only really after the second world war that modern day food additives really came to the fore.

With artificial sweeteners produced by the petro-chemical industry, and with new preservatives and anti-fungal agents to keep packaged food on the shelf for longer, we created the modern phenomenon of ultra processed foods. The absolute antithesis of Slow Food, these foods simply could not exist without their chemical additions.

So how is the science on these new foods catching up with Slow Food’s healthy scepticism of all artificial additives?

Recent scientific reviews emphasize that the microbiome–additive interaction is a blind spot in regulation. Additives are rarely evaluated for their long‑term impact on microbial ecology and host–microbe relationships (gut health, in simple terms), even though these are key determinants of metabolic and immune health.

These additives are designed to inhibit moulds, bacteria, and other microbes are safety tested on human cells. However, the human body, with its gut microbiome is made up of more microbial cells than human ones.

And these are the very type of cells that these additives are designed to interrupt.

Gut health

A 2020 study in the European Journal of Nutrition examined the impact of common food additives and artificial sweeteners on the human gut microbiome and its fermentation of fibre.

The authors reported that several additives and sweeteners significantly altered microbial composition and reduced the production of beneficial short‑chain fatty acids (SCFAs), which are crucial for colon health, energy metabolism, and immune regulation.

A 2024 review in Microbiota and Health Disease summarized newer research findings, concluding that preservatives and other additives can shift microbial communities toward potentially pro‑inflammatory profiles. The latter is a risk factor for conditions like chronic gut inflammation.

Glucose intolerance

Artificial sweeteners such as saccharin, sucralose, and others in multiple human and animal studies have been linked to impaired glucose tolerance.

The 2020 European Journal of Nutrition paper noted that these sweeteners can reduce microbial diversity and alter fermentation patterns in vitro, potentially explaining metabolic disturbances observed in the human body. This suggests that “zero‑calorie” does not mean “metabolically neutral” when microbiome interactions are considered.

Allergies and immune disorders

Emulsifiers are used to keep ingredients like oil and water mixed in processed foods, supplements, and pharmaceuticals. A 2025 article summarizing research published in Allergologia et Immunopathologia reported that emulsifiers can disrupt intestinal barrier function, promote low‑grade inflammation, and are increasingly being linked to allergy and immune disorders. Allergies are, of course, at an all time high, and seemingly within a single generation or two.

Between 5 and 8 per cent of children in the UK live with a food allergy.

This is too fast for a genetic cause, so must have an environmental cause: what we eat, drink, breathe, or come into contact with.

The cocktail effect

Of course, when we consume ultra-processed foods, we are rarely exposed to a single additive in isolation. Ultra‑processed foods typically contain multiple additives: emulsifiers, preservatives, colorants, sweeteners, and stabilizers, all alongside high levels of refined carbohydrates and fats. We can think of this as a cocktail effect. This is almost impossible to evaluate for human safety.

This means we return, as we always do, to eating real food. Food that is recognisable as food, food which, if it has been preserved, has been preserved in a manner that would be recognised by our grand-parents and their parents.

We will always advocate food that is shared around the table, with people that we love, food that not only nourishes us and our soul, but our microbiomes too.

 

This is the second article in a series on this topic. To read the first article click here

Nothing in this article should be considered medical advice. The article takes the perspective of health and disease at a population level where it is possible to draw conclusions across large numbers of individuals, and not an individual one. If you have concerns about your health please speak to your GP.