Diet may influence the MS disease process, including direct effects on the immune system, indirect effects through the gut microbiome, and effects on components of the central nervous system. While many diets in MS have been investigated, specific dietary components have also been studied. Here we outline some main dietary components that have been studied the most thoroughly in MS—salt, gluten and dairy—and provide an explanation of what that may mean for people with MS.
Research on Specific Dietary Components in MS
Before reading the details on the studies below, it may be helpful to read our Guide to Understanding Research Studies so you can better understand the terminology used.
Study: Farez et al., 2014
Participants: Initial group (n=70) people with MS. The same study was replicated in a second group (n=52).
Length: 2 years
Details: Sodium was measured in urine and a formula was used to calculate daily sodium intake. Participants’ sodium levels for the initial group were classified as low (n=21, <2 grams/day), average (n=37, <2-4.8 grams/day) and high (n=12, >4.8 grams/day). Those in the high and medium sodium groups had more MS relapses and more new brain lesions on MRI than the low sodium group. Similar results were found in the second group. The strengths of this study were objective measurements, longitudinal design and relatively long duration. The limitations were observational design (no intervention) and relatively small sample size.
Study: Fitzgerald et al., 2017
Participants: n=465 with clinically isolated syndrome
Length: 5 years
Details: Sodium was measured in participants’ urine and a formula was used to calculate daily sodium intake. No association was detected between sodium intake and MS relapse, new MRI lesions, or change in disability score. The strengths of this study were long duration, large sample size, longitudinal design, and objective measurement for sodium intake. The limitation was that this was observational only (no intervention).
Study: Nourbakhsh et al., 2016
Participants: n=174 pediatric participants with relapsing remitting MS (average age 15 years)
Length: 1.8 years
Details: A food frequency questionnaire (Block Kids Food Screener) was administered to participants to estimate sodium intake. No association was detected between sodium intake and MS relapse rate. Strengths of the study included longitudinal design and relatively large sample size. Limitations of the study were that it was observational only (no intervention) and participants potentially underestimated/underreported sodium intake.
What This Means:
It is currently unclear whether salt is specifically harmful in MS. However, diets high in salt are often from processed foods, which should be limited to benefit overall health.
Study: Rodrigo et al., 2014
Participants: n=72 with relapsing remitting MS, where 36 followed the gluten free diet (GFD) and 36 “controls” who started the GFD, but did not adhere to the diet
Length: 4.5 years of follow up
Details: Participants self-selected whether they followed a GFD (intervention) or a regular diet (control). The GFD group had less MRI activity and lower disability scores compared to controls. The strengths of the study were relatively long study duration and interventional design. This study has a high risk of bias and the results should be interpreted very cautiously, due to lack of randomization (self-selection into groups) and relatively small sample size.
What This Means:
It is currently unclear whether gluten has any relationship to MS. Not everyone with MS has a gluten intolerance. Those who do not tolerate gluten should avoid it by not consuming foods with gluten. Highly processed “gluten-free” foods are often not healthy and should be limited to benefit overall health.
Study: Hadgkiss et al., 2015
Participants: n=2087 with MS
Length: cross-sectional (measurement at a single point in time)
Details: Participants completed a dietary questionnaire including questions on dairy consumption. Compared to those who reported consuming dairy, those who did not consume dairy reported less disability and less MS disease activity. The strength of this study is the large number of participants. The limitations were the study was an observational only, cross-sectional design, with self-reported estimates for dairy intake and disease measures.
Study: Fitzgerald et al., 2018
Participants: n=6989 with MS
Length: Cross-sectional (measurement at a single point in time)
Details: Participants completed a dietary questionnaire including questions on dairy consumption. As compared to those with lower dairy intake, those with higher dairy intake reported lower MS disability. The very large sample size is a strength of the study. The limitations were the study was an observational only, cross-sectional design, with self-reported estimates for dairy intake and disease measures.
What This Means:
It is currently unclear whether dairy is helpful, harmful, or neutral with respect to MS. It is possible that different types of dairy (for example, yogurt vs. ice cream) affect MS differently but this is not yet known. Not everyone with MS is dairy intolerant. Those who do not tolerate dairy should avoid it by avoiding dairy-containing foods. Highly processed dairy substitutes (example: certain dairy free “yogurts” and “cheeses”) should be limited to benefit overall health.