REPORT FROM THE ACTRIMS-ECTRIMS – BOSTON, MA, SEPTEMBER 10-13, 2014 – Recent studies have indicated that increased sodium chloride concentrations can induce pathogenic CD4+ Th17 cells in humans (Kleinewietfeld et al. Nature 2013;496:518-522; free full text at www.ncbi.nlm.nih.gov/pmc/articles/PMC3746493/pdf/nihms500370.pdf). This effect is specific to Th17, with little or no effect on Th1 or Th2 differentiation or proliferation. Moreover, salt-induced Th17 cells demonstrate increased production of pro-inflammatory cytokines, such as TNF-alpha and IL-2.

A new study reports that higher salt consumption is associated with increased clinical and radiological disease activity in MS patients (Farez et al. ECTRIMS 2014; abstract P351). Urine samples were obtained from 70 RRMS patients to quantify sodium excretion and consumption over a two-year period. Mean patient age was 37.5 years; median duration of MS was 5 years; and median EDSS was 1. Patients with a moderately high sodium intake (2-4.8 g/day) had a 2.75-fold higher relapse rate compared to those with a low (< 2 g/day) sodium intake. A high sodium intake (>4.8 g/day) was associated with a 3.95-fold higher relapse rate. Moreover, patients with  medium or high sodium intake had a 2.86- and 3.42-fold risk of developing a new lesion on MRI. The mean T2 lesion load was 6.45 in the low-sodium group, 7.14 in the medium-sodium group, and 14.13 in the high-sodium group; differences were significant between the high and low sodium groups. Results were replicated in a second group of 52 patients.

However, a separate case-control study evaluated dietary salt intake in 138 pediatric MS patients versus 285 healthy controls (McDonald et al. ECTRIMS 2014; abstract P348). There were significantly more females and Hispanics in the case group. No significant differences were seen in mean sodium intake between cases (1965 mg/day) and controls (2072 mg/day). In addition, the proportion of subjects exceeding the tolerable upper limit for sodium consumption was similar in the two groups. There was a trend to an increased risk of MS for each 100-mg increase in sodium intake, but results were not significant. Thus, it remains unclear if dietary salt consumption is an environmental risk factor for the development of MS.

Guest Reviewer: Dr. Daniel Selchen, St. Michael’s Hospital, Toronto, Ontario.