Dietary interventions for multiple sclerosis
Abstract
Background
Clinical and experimental data suggest that certain dietary regimens, particularly those including polyunsaturated fatty acids (PUFAs) and vitamins, might improve outcomes in people with multiple sclerosis (MS). Diets and dietary supplements are much used by people with MS in the belief that they might improve disease outcomes and overcome the effectiveness limits of conventional treatments.
This is an update of the Cochrane review "Dietary intervention for multiple sclerosis" (first published on The Cochrane Library 2007, Issue 1).
Objectives
To answer MS patients' questions regarding the efficacy and safety of dietary regimens for MS. Can changes in dietary habits be an effective intervention for MS patients? Are the potential side effects of these interventions known, and have they been measured? Are potential interactions between dietary interventions and other curative or symptomatic treatments known and have they been studied?
Search methods
We searched the Cochrane Multiple Sclerosis and Rare Diseases of the Central Nervous System Group Specialised Register (November 2011), CENTRAL (The Cochrane Library 2011, Issue 4), MEDLINE (PubMed) (1966 to November 2011), EMBASE (embase.com) (1974 to November 2011) and reference lists of papers found.
Selection criteria
All controlled trials (randomised controlled trials (RCTs) and controlled clinical trials (CCTs)) on a specific dietary intervention, diet plan or dietary supplementation, except for vitamin D supplementation, compared to no dietary modification or placebo were eligible.
Data collection and analysis
Two review authors independently selected articles, assessed trial quality and extracted data. Data were entered and analysed in RevMan.
Dichotomous data were summarised as relative risks (RR) with 95% confidence intervals (95% CI) using a random‐effects model in the presence of heterogeneity (I² > 60%). Continuous data were analysed using weighted mean differences, determined by the difference between the pre‐ and post‐intervention changes in the treatment and control groups.
Main results
Six RCTs that investigated PUFAs emerged from the search strategy, accounting for 794 randomised patients.
PUFAs did not have a significant effect on disease progression at 24 months. Omega‐6 fatty acids (11 to 23 g/day linoleic acid) didn't show any benefit in 144 MS patients (RR 1.04, 95% CI 0.66 to 1.63). Linoleic acid (2.9 to 3.4 g/day) had no benefit in 65 chronic progressive MS patients (RR 0.78, 95% CI 0.43 to 1.42). Omega‐3 fatty acids had no benefit in 292 relapsing remitting MS patients (RR 0.82, 95% CI 0.65 to 1.03, P = 0.08).
Slight potential benefits in relapse outcomes were associated with omega‐6 fatty acids in some studies, however these findings were limited by the reduced validity of the endpoints. No judgements about safety or patient‐reported outcomes were possible. In general, trial quality was poor.
No studies on vitamin supplementation and allergen‐free diets were analysed as none met the eligibility criteria, mainly due to lack of clinical outcomes.
Authors' conclusions
PUFAs seem to have no major effect on the main clinical outcome in MS (disease progression), but they may tend to reduce the frequency of relapses over two years. However, the data that are available are insufficient to assess a real benefit or harm from PUFA supplementation because of their uncertain quality.
Evidence on the possible benefits and risks of vitamin supplementation and antioxidant supplements in MS is lacking. More research is required to assess the effectiveness of dietary interventions in MS.
PICOs
Plain language summary
Dietary interventions as complementary therapies for multiple sclerosis (MS)
Because available conventional treatments are only partially effective and may produce side effects, most patients with MS use therapies proposed by complementary and alternative medicine, usually special diets and dietary supplements. In fact, an Internet search using the terms 'diet' and 'multiple sclerosis' produces over 27 million links, indicating that these treatments are widely used and believed in by the MS patient community. The most common dietary interventions are supplementation with polyunsaturated fatty acids (PUFA), allergen‐free (gluten and milk) diets, vitamins, and micronutrients and antioxidants such as selenium, Gingko biloba extracts and coenzyme Q10.
The authors of this review tried to assess whether changes in dietary habits could favourably influence the prognosis for people with MS. Although a massive amount of data has been published in this area, only six controlled studies on PUFA, comprising a total of 794 patients, met the inclusion criteria in terms of methodological quality for this review. No studies on vitamins and antioxidant supplements were found that met our criteria. No papers on any other proposed dietary interventions for MS were found after extensive searching of the scientific databases.
The available data are insufficient to assess any potential benefit or harm that might result from PUFA supplementation. The absence of evidence on PUFA and the extensive lack of data on other supplements is an unfortunate event since 50% to 75% of people with MS do use dietary regimens and supplements.
