Move over football, a new national obsession has taken hold across Britain: the state of our guts. Once niche health foods like kefir, kombucha, kimchi, and sauerkraut have vaulted from specialist delis into mainstream supermarket aisles, driven by a surge of public interest.
This fascination stems from emerging science highlighting the critical role of the gut microbiome—the vast community of bacteria lining our intestines—in our overall wellbeing. Research now shows a healthy gut can influence everything from immune function and metabolism to mental health, explaining why the topic has never been more prominent.
The clinical need is clear. Gut symptoms are responsible for one in eight visits to GPs, with related problems on the rise. A report in BMC Gastroenterology noted a striking 34 per cent increase in cases of inflammatory bowel disease, including Crohn's and ulcerative colitis, over a decade. Meanwhile, surveys suggest up to half the population experiences acid reflux, and food intolerances are becoming more common.
While experts consistently advise building good bacteria by consuming probiotic and prebiotic-rich foods, they equally stress that avoiding certain items is just as crucial for a robust microbiome. The foods that cause the most damage to gut bacteria and disrupt digestion might surprise you.
The Supermarket Loaf: A Stealthy Gut Foe
It's widely accepted that ultra-processed foods—typically high in fat, sugar, and encased in plastic—are bad for digestive health. However, one household staple often flies under the radar, warns gastrointestinal physiologist Jordan Haworth from the Functional Gut Clinic.
"A lot of supermarket breads are surprisingly bad for the gut due to their high content of synthetic emulsifiers," he explained. These additives, used to add bulk and improve texture, are common in products from cakes to children's yoghurts.
Experts suggest emulsifiers can disrupt the protective lining of the gut, potentially creating gaps. This is thought to heighten the risk of bacterial infections, some of which may trigger the development of bowel cancers. While natural emulsifiers like lecithin are less harmful, most mass-produced breads use synthetic versions for better dough strength and shelf life.
Furthermore, the processing of white bread strips out fibre, which is vital for feeding beneficial bacteria and removing toxins, leading to poor microbial diversity. "Supermarket loaves can displace whole grains in the diet, meaning you eat less fibre and more sugar, fat, and additives," Mr Haworth added, noting that big-brand, pre-packaged loaves are often the worst offenders.
Even supermarket sourdough has faced scrutiny. Last year, renowned nutrition scientist Professor Tim Spector, founder of the Zoe app, cautioned that many loaves labelled 'sourdough' use commercial yeasts, flavourings, and emulsifiers to mimic the real thing quickly, creating a misleading "health halo." For a safer choice, Mr Haworth recommends buying from a local bakery or carefully checking labels for additives and opting for multi-grain varieties.
Ice Cream and Artificial Sweeteners: A Double Blow
The stomach ache from overindulging in ice cream is familiar to many. While its richness and high sugar content are partly to blame, Mr Haworth points to another culprit: emulsifiers. Used to create a smooth texture and prevent ice crystals, common synthetic emulsifiers in shop-bought ice cream include mono- and diglycerides (E471), carrageenan, and polysorbate 80 (E433).
Compounding the issue, an estimated 10 per cent of Brits have some level of dairy intolerance. For them, the lactose in ice cream ferments in the colon, causing bloating, gas, and diarrhoea. A healthier alternative, says Mr Haworth, is fermented yoghurt like kefir or Greek yoghurt. These introduce beneficial live bacteria, support the gut lining, and data shows consumers of fermented dairy typically have lower inflammation levels.
The quest for healthier options leads many to low-sugar sodas and sweets, but experts warn artificial sweeteners bring their own problems. Animal studies indicate sweeteners can alter the gut microbiome, reducing good bacteria and increasing harmful ones, while also weakening the intestinal lining.
"If you're overweight or want to maintain your weight, you're probably going to be eating more sweeteners," says Mr Haworth. "This can negatively impact the gut microbiome as well as metabolism." A 2023 human study found popular sweeteners sucralose and saccharin altered both gut bacteria and blood sugar processing. While aspartame wasn't found to disrupt the microbiome, it has been classified as possibly carcinogenic.
Mr Haworth states one Diet Coke a day is acceptable, but for those drinking more, switching to a fermented drink like kombucha is wiser. Nutritionist Adrienne Benjamin adds that 'mindful' low-sugar chocolates and gummies often rely on sugar alcohols like erythritol and sorbitol, which are "notorious for impacting digestion" and can cause significant gut discomfort.
Vegan Cheese, Oysters, and Fried Foods
For plant-based eaters, vegan cheese remains a staple, but its ingredient list can be gut-irritating. "Many faux cheeses are made with refined oils, starches and stabilisers that offer little nutritional value," explained Ms Benjamin. They also lack the live cultures found in fermented dairy. Experts advise seeking brands made primarily from whole foods like nuts, seeds, or vegetables, which provide more fibre and healthy fats.
Perhaps the single worst item for gut health, however, is any food that might cause food poisoning—with oysters topping the list. "Food poisoning and tummy bugs are the single biggest cause of long-term gut issues like irritable bowel syndrome (IBS)," Mr Haworth emphasised. Bacterial toxins trigger inflammation and nerve overstimulation, and the immune response can sometimes attack healthy gut cells, compounding damage.
He personally avoids raw oysters due to the risk of viruses from water, a concern heightened by rising UK sewage spills. "Nowadays, I won't eat them unless they're fully cooked," he stated.
Finally, fried foods pose a significant threat. "When you fry oils at high temperatures they become oxidised," Mr Haworth explained. "These oxidised compounds have been linked to negative changes in the gut microbiome." The fats used are also harder to digest, leading to gas, pain, and diarrhoea. His advice is to limit fried food and, when cooking, use extra virgin olive oil, as its polyphenols help protect food from oxidising.
The message from experts is clear: nurturing gut health is as much about strategic avoidance as it is about conscious consumption. By scrutinising everyday choices, from the bread bin to the freezer, Brits can take meaningful steps towards a happier, healthier digestive system.
