Ultra-processed foods are defined by the NOVA classification system as industrially formulated food products that are manufactured using substances not typically used in home cooking, including hydrogenated oils, maltodextrin, hydrolysed protein, artificial flavours, and various classes of stabilisers, emulsifiers, and preservatives. Their dominant market position explains why the average UK adult obtains approximately 57 percent of calories from ultra-processed foods.
The Specific Damage Mechanisms
- Emulsifiers carboxymethylcellulose and polysorbate-80: added to maintain texture stability in processed foods; a 2015 study in Nature found that these two emulsifiers, at doses achievable from dietary exposure, directly eroded the gut mucosal layer and altered gut microbiome composition toward a pro-inflammatory profile, inducing metabolic syndrome and low-grade colitis in mice and consistent changes in human gut microbiome studies
- Artificial sweeteners: saccharin, sucralose, and aspartame alter gut microbiome composition toward glucose-intolerant profiles in a 2022 Nature RCT, demonstrating effects through microbiome disruption rather than direct metabolic action
- Carrageenan: a thickener used in dairy alternatives and deli meats; activates TLR4 inflammatory signalling in gut epithelial cells at dietary exposure concentrations
- Titanium dioxide: E171, used as a whitening agent; impairs tight junction proteins in the gut epithelium in human cell studies, increasing gut permeability
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