Artificial sweeteners
"Artificial sweeteners, like sucralose and saccharin, can disrupt gut
microbiota and impair glucose metabolism, potentially leading to
metabolic disorders like diabetes," says Amati. These low-calorie
sugar substitutes are often found in products that are labelled "diet"
or "sugar-free". Studies also link intake with increased risk of
cardiovascular disease and unnecessary appetite stimulation. When
buying supermarket products, be wary of low-sugar marketing claims and
prioritise eating whole foods (raspberries are a great high-fibre,
low-sugar snack) over processed foods and diet drinks. Swap fizzy
beverages (which are often full of artificial sweeteners) for
Dalston’s Soda or Momo’s raw and unfiltered kombucha, which is also
great for gut health.

High-fructose corn syrup
High-fructose corn syrup (HFCS) is a sweetener commonly found in
processed foods, fizzy drinks, sweets, sauces, breakfast cereals,
baked goods and even certain yoghurts and flavoured dairy products in
the UK, and especially in the US. It is inflammatory, "disrupts the
metabolism and contributes to insulin resistance, blood sugar
instability, obesity and type 2 diabetes," says Rhian Stephenson,
nutritionist, naturopath and founder of Artah, which sells supplements
and nutrition programmes. "It also offers little nutritional value and
negatively affects energy levels, hormones and metabolic health."

In the UK, HFCS may appear on labels as glucose-fructose syrup or
isoglucose, but elsewhere it goes by other names, such as maize syrup.
Stephenson advises reading full ingredient lists, "not just the front
label, because marketing claims – such as 'natural' or 'low fat' - can
be misleading," she says. "In fact, they are usually a warning sign."
For some extra assistance, Amati recommends the Zoe processed food
risk scale, a science-backed tool that offers guidance on what’s in
processed foods. Ultimately, cooking whole foods at home is the best
way to avoid HFCS and similar additives.

Emulsifiers
Widely used to improve the texture and shelf life of packaged foods,
emulsifiers have "been shown (in animal studies) to cause gut
inflammation and glucose intolerance, and many worsen intestinal
diseases like ulcerative colitis", says Amati. It is found in products
such as ice-cream, mayonnaise, chocolate, packaged bread and oat milk
(common examples include polysorbate 80, carboxymethyl cellulose or
CMC and carrageenan). Emulsifier-free supermarket buys include Jason’s
Sourdough (which also doesn’t contain sweeteners), Plenish’s Oat Milk,
Yeo Valley’s Organic Vanilla Ice-Cream and Kallo’s Belgian Milk
Chocolate Organic Rice Cake Thins. While currently deemed safe in
small amounts, emulsifiers are worth watching as research in humans
evolves.

Nitrites
Whether it’s bacon, salami or hotdogs, most processed meats are
preserved using nitrites. These can form carcinogenic nitrosamines in
the body, and have been scientifically linked to an increased risk of
colorectal cancer, rates of which are rising globally. The World
Health Organization advises limiting intake, and to be particularly
wary of heating them above 130C, which is when nitrosamines can form –
and have been linked to stomach and bowel cancer.