Ultra-processed foods linked to cognitive decline and depression
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- Multiple large cohort studies link higher ultra-processed food (UPF) intake to cognitive decline and stroke, including a 2024 study of ~30,000 people showing each 10% rise in the proportion of UPFs in a person's diet significantly raised the risk of cognitive impairment and stroke, even after adjusting for income, alcohol, and activity.
- A Brazilian study of 10,775 adults followed for ~8 years found participants getting more than 19.9% of their energy from UPFs experienced faster declines in global cognition and executive function, with the effect especially pronounced in people under 60.
- A 2025 analysis of 58,423 people aged 40-70 found increased UPF consumption associated with a higher risk of dementia, Parkinson's disease, and multiple sclerosis.
- A 2003–2017 study of 31,712 female nurses free of depression at baseline found those eating more than 8.8 daily servings of UPFs had a 49% higher risk of developing depression, with advanced statistical analyses used to broadly rule out reverse causality.
- Researchers propose overlapping mechanisms — gut microbiome disruption, low-grade inflammation from high-fat/high-sugar diets, and altered brain insulin signaling — supported by a small study showing just five days of an extra 1,500 calories from UPF snacks modified men's brain responses to insulin, an effect still detectable a week after returning to normal diets.
- Early evidence also links high-UPF diets to reduced hippocampal volume in adults, possibly because the foods carry fewer nutrients vital for brain growth, offering another pathway to the cognitive decline seen in larger studies.
- Tim Spector of Kings College London argues current studies likely underestimate the harms because the NOVA classification groups nutritionally different products — like plain Weetabix and sugary energy drinks — together, while practical advice from experts favors adding fiber and oily fish (trout, sardines, chia or flax seeds) over trying to eliminate every UPF.
Why it matters: The strongest evidence clusters around midlife: the Brazilian cohort saw the steepest cognitive decline in participants under 60, suggesting dietary changes in one's 30s and 40s could matter most. For consumers, the article shifts the conversation from total UPF avoidance to a cheaper, more sustainable target — reducing products that combine added sugar, high salt, and low fiber, and adding oily fish and fiber sources like sardines, chia seeds, or even a daily coffee.
