Which Diets Actually Help MS Patients Think More Clearly

Cognitive impairment affects roughly 40-70% of the 2.8 million people with multiple sclerosis worldwide. Slowed information processing is the hallmark deficit, and attention, memory and executive function are often affected too. These problems can appear early and progress independently of physical disability, hurting employment, social life and quality of life. Disease-modifying therapies reduce relapses, but a 2020 meta-analysis found no significant cognitive benefit from cholinesterase inhibitors, stimulants, fampridine or herbal remedies. That gap has driven interest in diet, which influences inflammation, oxidative stress, the gut microbiome and metabolic health.

The authors followed PRISMA 2020 and registered the review in PROSPERO (CRD420251156238). They searched PubMed, Scopus, Embase and Web of Science, with a manual update in September 2025. Of 380 records screened, 27 went to full-text review and 18 articles (16 studies) were included. Seven articles from five studies were randomized trials, four were non-randomized interventional studies, and seven were observational. Isolated supplement trials were excluded. Risk of bias was assessed with JBI tools. Meta-analysis was judged inappropriate because of heterogeneity in diets and cognitive endpoints.

Mediterranean diet trials were largely neutral. In a one-year randomized trial in Iran (56 completers), no differences emerged on most MACFIMS tests, and one visuospatial memory score was higher in the standard-diet group. A six-month pilot in 36 women with MS showed no change in the MACFIMS composite despite 90.3% self-reported adherence and 94.4% completion. In contrast, a 2025 Italian trial (80 of 120 participants completed) found SDMT processing speed changed over time with Mediterranean-based diets versus a stable control group, with no difference between the three diet variants.

Wahls and Swank diets performed best. In a 36-week randomized trial (77 completers), both diets significantly reduced perceived cognitive fatigue on the MFIS cognitive scale at 12 and 24 weeks, and both raised SDMT scores and lowered perceived deficits, with no difference between them. Adherence at 24 weeks was 81.1% for Swank and 74.3% for Wahls. A three-arm pilot (14 participants) found higher PASAT scores at 12 weeks on the modified Paleolithic diet but not on a ketogenic version, even though ketosis was confirmed. A single-arm progressive-MS pilot (19 participants) showed most cognitive scores improving by 12 months. Time-restricted eating (11 participants, 8-hour window) and a six-month ketogenic diet (13 completers, self-reported cognition) hinted at benefit. A fruit-and-vegetable app program (800 g/day) showed none.

Observational data were inconsistent. In a registry of 6,989 people, diet quality was not linked to self-reported cognitive symptoms. In a 2,464-person survey, better diet quality was associated with less cognitive impairment, independent of age, sex, education, disability, fatigue and depression. Among 563 people, higher Mediterranean adherence predicted better SDMT and fewer perceived deficits. In another cohort (162 participants), a cross-sectional link vanished over 7.5 years of follow-up. Moderate, but not high, fiber intake was associated with fewer cognitive symptoms in one cohort of 1,490.

The authors conclude diet may be a useful adjunct for cognitive health in MS but that strong recommendations are not justified. Trials were mostly small pilots and many lacked control groups. Several relied on self-reported cognition, lacked allocation concealment or blinding, and ran for 8 weeks to 12 months, with depression only variably assessed. Larger, longer randomized trials with standardized neuropsychological batteries are needed.