Dietary interventions for multiple sclerosis-related outcomes

Background: Multiple sclerosis (MS) is a common demyelinating disease of the central nervous system. Although the exact pathogenesis remains unknown, the leading theory is that it results from immune system dysregulation. Approved disease-modifying therapy appears to modulate the immune system to improve MS-related outcomes. There is substantial interest in the ability of dietary interventions to influence MS-related outcomes. This is an update of the Cochrane Review 'Dietary interventions for multiple sclerosis' (Farinotti 2003; Farinotti 2007; Farinotti 2012). Objectives: To assess the effects of dietary interventions (including dietary plans with recommendations for specific whole foods, macronutrients, and natural health products) compared to placebo or another intervention on health outcomes (including MS-related outcomes and serious adverse events) in people with MS. Search methods: On 30 May 2019, we searched CENTRAL, MEDLINE, Embase, and Web of Science. We also searched ClinicalTrials.gov, World Health Organization International Clinical Trials Registry Platform (ICTRP), and Networked Digital Library of Theses and Dissertations (NDLTD). We checked reference lists in identified trials and requested information from trial authors to identify any additional published or unpublished data. Selection criteria: We included any randomized controlled trial (RCT) or controlled clinical trial (CCT) examining the effect of a dietary intervention versus placebo or another intervention among participants with MS on MS-related outcomes, including relapses, disability progression, and magnetic resonance imaging (MRI) measures. Data collection and analysis: We used standard methodological procedures expected by Cochrane. Planned primary outcomes were number of participants experiencing relapse and change in disability progression, according to a validated disability scale at the last reported follow-up. Secondary outcomes included MRI activity, safety, and patient-reported outcomes. We entered and analysed data in Review Manager 5. Main results: We found 41 full-text articles examining 30 trials following full-text review. Participants were adults with MS, defined by established criteria, presenting to MS clinics in Europe, North America, and the Middle East. Study design varied considerably, although all trials had at least one methodological issue leading to unknown or high risk of bias. Trials examined: supplementation to increase polyunsaturated fatty acids (PUFAs) (11 trials); a variety of antioxidant supplements (10 trials); dietary programmes (3 trials); and other dietary supplements (e.g. acetyl L-carnitine, biotin, creatine, palmitoylethanolamide, probiotic, riboflavin) (6 trials). In three trials comparing PUFAs with monounsaturated fatty acids (MUFAs), the evidence was very uncertain concerning difference in relapses (risk ratio (RR) 1.02, 95% confidence interval (CI) 0.88 to 1.20; 3 studies, 217 participants; 75% in the PUFA group versus 74% in the MUFA group; very low-certainty evidence). Among four trials comparing PUFAs with MUFAs, there may be little to no difference in global impression of deterioration (RR 0.85, 95% CI 0.71 to 1.03; 4 studies, 542 participants; 40% in the PUFA group versus 47% in the MUFA group; low-certainty evidence). In two trials comparing PUFAs with MUFAs (102 participants), there was very low-certainty evidence for change in disability progression. None of the PUFA versus MUFA trials examined MRI outcomes. In one trial comparing PUFAs with MUFAs (40 participants), there were no serious adverse events; based on low-certainty evidence. In two trials comparing different PUFAs (omega-3 versus omega-6), there may be little to no difference in relapses (RR 1.02, 95% CI 0.62 to 1.66; 2 studies, 129 participants; 30% in the omega-3 versus 29% in the omega-6 group; low-certainty evidence). Among three trials comparing omega-3 with omega-6, there may be little to no difference in change in disability progression, measured as mean change in Expanded Disability Status Scale (EDSS) (mean difference (MD) 0.00, 95% CI -0.30 to 0.30; 3 studies, 166 participants; low-certainty evidence). In one trial comparing omega-3 with omega-6, there was likely no difference in global impression of deterioration (RR 0.99, 95% CI 0.51 to 1.91; 1 study, 86 participants; 29% in omega-3 versus 29% in omega-6 group; moderate-certainty evidence). In one trial comparing omega-3 with omega-6 (86 participants), there was likely no difference in number of new T1- weighted gadolinium-enhancing lesions, based on moderate-certainty evidence. In four trials comparing omega-3 with omega-6, there may be little to no difference in serious adverse events (RR 1.12, 95% CI 0.38 to 3.31; 4 studies, 230 participants; 6% in omega-3 versus 5% in omega-6 group; low-certainty evidence). In four trials examining antioxidant supplementation with placebo, there may be little to no difference in relapses (RR 0.98, 95% CI 0.59 to 1.64; 4 studies, 345 participants; 17% in the antioxidant group versus 17% in the placebo group; low-certainty evidence). In six trials examining antioxidant supplementation with placebo, the evidence was very uncertain concerning change in disability progression, measured as mean change of EDSS (MD -0.19, 95% CI -0.49 to 0.11; 6 studies, 490 participants; very low-certainty evidence). In two trials examining antioxidant supplementation with placebo, there may be little to no difference in global impression of deterioration (RR 0.99, 95% 0.50 to 1.93; 2 studies, 190 participants; 15% in the antioxidant group versus 15% in the placebo group; low-certainty evidence). In two trials examining antioxidant supplementation with placebo, the evidence was very uncertain concerning difference in gadolinium-enhancing lesions (RR 0.67, 95% CI 0.09 to 4.88; 2 studies, 131 participants; 11% in the antioxidant group versus 16% in the placebo group; very low-certainty evidence). In three trials examining antioxidant supplementation versus placebo, there may be little to no difference in serious adverse events (RR. 0.72, 95% CI 0.17 to 3.08; 3 studies, 222 participants; 3% in the antioxidant group versus 4% in the placebo group; low-certainty evidence). Authors' conclusions: There are a variety of controlled trials addressing the effects of dietary interventions for MS with substantial variation in active treatment, comparator, and outcomes of interest. PUFA administration may not differ when compared to alternatives with regards to relapse rate, disability worsening, or overall clinical status in people with MS, but evidence is uncertain. Similarly, at present, there is insufficient evidence to determine whether supplementation with antioxidants or other dietary interventions have any impact on MS-related outcomes.