Diet-induced changes in functional disability are mediated by fatigue in relapsing-remitting multiple sclerosis: A secondary analysis of the WAVES randomized parallel-arm trial.

Background: People with multiple sclerosis (MS) often report dietary modifications; however, evidence on functional outcomes remains sparse. Objective: Evaluate the impact of the low-saturated fat (Swank) and modified Paleolithic elimination (Wahls) diets on functional disability among people with relapsing-remitting MS. Methods: Baseline-referenced MS functional composite (MSFC) scores were calculated from nine-hole peg-test (NHPT), timed 25-foot walk, and oral symbol digit modalities test (SDMT-O) collected at four study visits: (a) run-in, (b) baseline, (c) 12 weeks, and (d) 24 weeks. Participants were observed at run-in and then randomized at baseline to either the Swank (n = 44) or Wahls (n = 43) diets. Results: Among the Swank group, MSFC scores significantly increased from -0.13 ± 0.14 at baseline to 0.10 ± 0.11 at 12 weeks (p = 0.04) and 0.14 ± 0.11 at 24 weeks (p = 0.02). Among the Wahls group, no change in MSFC scores was observed at 12 weeks from 0.10 ± 0.11 at baseline but increased to 0.28 ± 0.13 at 24 weeks (p = 0.002). In both groups, NHPT and SDMT-O z-scores increased at 24 weeks. Changes in MSFC and NHPT were mediated by fatigue. Discussion: Both diets reduced functional disability as mediated by fatigue. Trial Registration: Clinicaltrials.gov Identifier: NCT02914964.