ACTRIMS 2017: What we know (and don’t know) about dietary factors and MS

The interaction between dietary factors and MS can be a tough nut to crack. On one hand, there is mounting evidence to show that certain nutrients and dietary factors can influence immune regulation and potentially modify the risk of MS or its disease course. On the other hand, dietary factors are notoriously challenging to study in a controlled clinical trial setting; diet trials are difficult to design, results can be influenced by a plethora of other factors (including physical activity, socioeconomic status, certain lifestyle habits, etc.), and individuals often find it challenging to adhere to the intervention plan. Nonetheless, there’s a great deal of high caliber research taking place that’s chipping away at the mysteries surrounding the relationship between certain dietary factors and MS risk and disease course. At this year’s ACTRIMS Forum, several experts in the field presented some of the latest data on this file.

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Dr. Ellen Mowry (Johns Hopkins University) presented a sweeping overview of what’s known (and what isn’t) about the association between vitamin D and MS – although it’s important to remember that diet represents only one source of vitamin D alongside sunlight exposure and supplementation. On the one hand, observational studies studying large groups of people have shown that lower levels of 25-hydroxyvitamin D (25(OH)D – the major circulating form of vitamin D used to determine vitamin D status – are associated with an increased risk of MS. In those already living with MS, lower 25(OH)D levels are linked to a greater risk of subsequent relapse, new lesions on imaging scans, and possibly greater disability progression and brain shrinkage.

Based on small, inconclusive pilot trails thus far, the influence of vitamin D supplementation on MS outcomes is still uncertain. Dr. Mowry presented preliminary data from the SOLAR trial, which is testing the effects of vitamin D supplementation (6,670 IU/day for 4 weeks followed by 14,000 IU/day for 44 weeks) as an add-on to interferon beta-1a (Rebif) on MS outcomes, versus placebo and Rebif. The data so far shows no significant effect of vitamin D supplementation on annualized relapse rate or NEDA (no evidence of disease activity – a composite score indicating no relapses, no EDSS change, and no new or enlarging lesions), although the vitamin D group did have fewer combined unique lesions on MRI compared to placebo. Overall, questions about vitamin D supplementation – such as how much to take, how often and for how long – for people living with or at risk of developing MS remain unanswered, although the MS Society is working with vitamin D and MS experts to provide more clarity for these questions.

Professor Ralf Linker (Friedrich-Alexander University Erlangen-Nuremberg) presented work on the link between dietary fats and risk of MS. Dietary fatty acids appear to have differing effects on measures of autoimmunity depending on their chain length (chains of carbon atoms linked by bonds). Long chain fatty acids promote the activity of disease-causing T cells such as Th1 and Th17 cells, whereas short chain fatty acids enhance the activity of regulatory T cells which are known to quiet down inflammation. Prof. Linker presented findings from both studies in mice with an MS-like disease and in human participants showing that propionate, a short chain fatty acid, can potentially improve MS disease outcomes. In a proof of concept study, participants living with MS and healthy controls were given propionate capsules for a period between 14-60 days (1g daily), and their immune cell profiles were analyzed. Propionate increased the proportion of beneficial regulatory T cells while decreasing disease-causing Th17 cells in all treated individuals, and these effects were sustained for 2-3 weeks after propionate treatment was stopped. These results suggest that intake of short chain fatty acids could potentially provide additional benefit as an add-on to treatment with disease modifying therapies, although further studies are needed to look at their effects on specific disease outcomes.

There’s mounting evidence to suggest that salt (specifically, sodium chloride) intake could influence MS disease course. Dr. David Hafler (Yale School of Medicine) presented findings from both animal and human studies showing that sodium chloride increases certain inflammatory markers like Th17 cells that are linked to the MS disease process while curbing the activity of beneficial regulatory T cells. Dr. Hafler dug even deeper to show the molecular mechanisms underlying this response, showing that blocking certain molecular pathways could undo the stimulation of disease-causing Th17 cells by sodium chloride. Interestingly, pairing high salt intake with increased fat intake – in essence mimicking a “fast food” diet – in mice similarly led to an increase in Th17 cells and a loss of regulatory T cells. Overall, high salt and fat intake appear to be linked to poorer immune responses. Although the benefits of dietary modifications for people living with MS on MS-specific outcomes are still unclear, strong evidence points toward lower salt intake in particular being beneficial for cardiovascular-related comorbidities, many of which are more prevalent in people with MS compared to the general population.

In addition to the challenges involved in testing the effects of certain dietary interventions on MS disease outcomes, little is known about what types of diets people with MS follow in the “real world”, their reasons for following these diets, and their perceived effectiveness. Dr. Kathryn Fitzgerald (Johns Hopkins Hospital) and a team of population health specialists conducted a survey among participants in the North American Research Committee on MS (NARCOMS) registry asking about 19 specific diets or diet plans – including Mediterranean, Swank, Wahl’s, Atkins, Weight Watchers, etc. – they followed since being diagnosed with MS. Of the 7,418 individuals who responded, 44% reported that they either currently or previously followed at least one diet plan. The highest proportion of respondents (21%) currently followed a gluten-free diet, whereas 45% previously followed a weight loss plan diet. 15% of individuals either currently or previously followed the Swank diet, and 8% currently or previously followed the Wahl’s diet. The perceived effectiveness of the different diet plans varied; 88% of those on the gluten-free diet felt that it was effective in helping their MS; 73% of those on a weight loss plan diet felt it was effective; 50% of those on the Swank diet considered it effective, and 61% of those on the Wahl’s diet thought it was effective. Overall, the study fills a gap in our knowledge about how different diet plans are approached and perceived among people living with MS.

What are your experiences with different diet plans? Leave your comments below.

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