4 observation studies: more Ultra-processed food, more Multiple Sclerosis

10% more UPF, 9% higher risk of MS - April 2026

Ultra-processed food consumption and multiple sclerosis incidence: A prospective cohort study

Clin Nutr. 2026 Apr 20:61:106673. doi: 10.1016/j.clnu.2026.106673.

Background & aims: Emerging evidence suggests an association between ultra-processed food (UPF) consumption and neurodegenerative diseases, but there is limited evidence for multiple sclerosis (MS). Diets rich in UPFs promote inflammation and oxidative stress that both play an important role in modulating the immune system, and thereby, potentially the pathogenesis of MS. This study aimed to investigate the longitudinal association between UPF consumption and MS onset in middle-aged and older adults.

Methods: The study included 185,788 adults who completed at least one valid dietary assessment and did not have MS at baseline (2009-2012). Dietary data was collected at 5 time points using a web-based 24-h dietary recall, and UPFs were categorised using the Nova food classification system. MS cases were identified based on medical history and linkage to data on hospital admissions (using ICD-coded diagnoses ICD10-g35; ICD9-3409), and self-reported MS diagnosis. Prospective associations between UPF consumption (as a percentage of total food intake in grams per day) and risk of MS onset were assessed using multivariable Cox proportional hazards models were adjusted for age, sex, ethnicity, education, Townsend deprivation index, smoking status, total energy intake and serum 25-hydroxyvitamin D.

Results: Participants had a mean age of 56.0 years (SD 8.0) and 54% were female. UPFs comprised 19.1% of total dietary grams intake, with carbonated drinks, ready-to- eat/heat meals and industrial-processed breads being the most consumed UPF subgroups. Over a mean follow-up of 8.9 years (SD: 2.7), 384 incident MS cases occurred. Each 10% increase in UPF consumption was associated with an estimated 9% increase in risk of MS (HR 1.09; 95% CI: 1.003 to 1.19; p-value = 0.04).

Conclusion: This study found a weak yet significant association between higher UPF consumption and increased risk of MS in middle-aged and older adults. Given the modest effect size and inconsistency of statistical significance across sensitivity analyses, these findings should be interpreted with caution. Research to confirm these findings in other population groups and contexts is needed.

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Claude AI May 2026: UPF and MS

Pavia, Italy (Guglielmetti 2023, cross-sectional) — Higher UPF consumption associated with moderate-to-high MS severity vs. lower consumption. OR 2.28 (95% CI 1.04–5.01) unadjusted, rising to OR 2.97 (95% CI 1.13–7.77) after adjustment for clinical confounders. Weakness: cross-sectional, single-center, ~150 patients, FFQ-based.

Ausimmune Study, Australia (case-control) — UPF consumption tested against likelihood of first clinical diagnosis of CNS demyelination (267 cases, 508 controls), a common precursor to MS, with propensity-score matching for the usual confounders (smoking, BMI, EBV/mono history, etc.). Positive association.

UK Biobank (prospective, n=58,423) — High UPF intake associated with incident multiple sclerosis (HR 2.38, 95% CI 1.02–5.55), alongside elevated risk for dementia and Parkinson's. The MS confidence interval is wide (case count is small) but this is the first prospective signal.

Canadian Pediatric Demyelinating Disease Network (case-control) — Higher ultra-processed food consumption associated with higher likelihood of paediatric-onset MS, NOVA-classified, Block Kids FFQ.

BENEFIT trial secondary analysis, Dalla Costa/Harvard, ECTRIMS 2025 — 451 CIS patients, 5-year follow-up, with UPF intake estimated from a validated metabolomic signature of 39 plasma metabolites rather than FFQ — a meaningful methodological upgrade. Highest vs. lowest UPF intake: RR 1.30 (95% CI 1.06–1.59) for relapses at 5 years; RR 1.08 for new active lesions at 2 years; larger T2 lesion volume increase. Notably, no difference in CIS→clinically definite MS conversion — so the signal is on disease activity/progression, not necessarily on triggering MS in the first place. Conference abstract; full manuscript pending.

So: 4 cohorts (Italy, Australia, UK, Canada) on incidence/likelihood + 1 on activity. Direction is consistent. None are RCTs; all share the usual residual-confounding concerns (UPF intake correlates with smoking, lower vitamin D, sedentariness, lower SES).

8 Plausible pathways

The mechanistic literature is well-developed for UPF→IBD and is being extended to MS. Multiple non-exclusive pathways:

  1. Emulsifier-driven barrier disruption. Polysorbate-80 and carboxymethylcellulose weaken the gut's mucus barrier, making it easier for microbes to cross in and out of the gut in murine models. Increased intestinal permeability ("leaky gut") permits LPS translocation → systemic inflammation → potential BBB compromise. Directly relevant to MS given growing evidence of gut–brain axis involvement.

  2. Microbiome dysbiosis. UPF-heavy diets reduce microbial diversity, lower levels of beneficial bacteria like Akkermansia muciniphila and Faecalibacterium prausnitzii, and increase pro-inflammatory microorganisms. Both species are key butyrate producers; Akkermansia depletion is independently reported in MS patients.

  3. SCFA depletion. Low fiber → reduced bacterial fermentation → less butyrate/propionate. These molecules help maintain the integrity of the intestinal barrier and regulate immune responses by dampening inflammation and helping produce T cells — specifically Treg induction. Propionate supplementation trials in MS (Duscha et al.) showed Treg increases and reduced relapse rates, supporting reverse direction.

  4. Th17 polarization via salt and additives. High dietary salt (a UPF hallmark) led to an increase in CD4+ T-cells, Th17 cells, and increased production of pro-inflammatory cytokines IL-17A and TNF-α. Th17/IL-17 is central to MS pathophysiology.

  5. Tight-junction disruption from additives independent of microbiome. Changes in intestinal tight junction permeability associated with industrial food additives have been proposed to explain rising autoimmune disease incidence broadly.

  6. Displacement of protective nutrients. Probably underweighted in mechanistic discussions but relevant to your work: UPF-heavy diets are inversely correlated with vitamin D status, omega-3 intake, polyphenols, and magnesium — each independently implicated in MS. Some of the "UPF effect" may be displacement of these protectives rather than a direct toxic effect of additives.

  7. Advanced glycation end-products (AGEs) from high-heat processing, plus acrylamide and other Maillard byproducts — RAGE signaling, oxidative stress.

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