by Rebecca Hiscott
A high intake of dietary salt, or sodium chloride, is associated with worsening multiple sclerosis (MS) symptoms, according a study published in the August 28 online issue of the Journal of Neurology, Neurosurgery & Psychiatry.
Researchers from the Raúl Carrera Institute for Neurological Research in Buenos Aires, Argentina, and the Brigham and Women’s Hospital Center for Neurologic Diseases in Boston, MA, conducted an observational study using a cohort of 70 patients with relapsing-remitting MS to examine the link between sodium intake and worsening of MS symptoms. Patients had brain and spinal cord MRIs at baseline, at three months and at six months, and researchers measured clinical, radiological and sodium intake data over a follow-up period of two years.
Patients were required to provide urine samples at three, six, and nine months to assess changes in salt consumption, and blood and urine samples were collected at 12 months. The researchers measured levels of sodium and creatinine – a marker of inflammatory activity – in the urine, as well as levels of serum sodium and vitamin D in the blood. They assessed patients’ disability status at baseline and at the end of the study, and looked for any development of new MS symptoms or worsening of pre-existing symptoms, confirmed via neurological examination. The primary outcome was defined as the number of relapses occurring over the two-year study period.
Intracranial and spinal cord lesions in multiple sclerosis. From: Yochum And Rowe's Essentials of Skeletal Radiology, Third Edition. Philadelphia: Lippincott Williams & Wilkins, 2004.
“We found a positive correlation between exacerbation rate and sodium intake in a multivariate model adjusted for age, gender, disease duration, treatment, vitamin D levels, BMI and smoking status,” the authors wrote.
They found that patients with a high sodium intake, defined according to World Health Organization (WHO) guidelines as more than 4.8 grams per day (g/day), had an exacerbation rate that was 3.95-fold higher than patients with the WHO recommended intake of 2 g/day or less. Patients with an average sodium intake (2 to 4.8 g/day) had a 2.75-fold higher exacerbation rate. Males were found to have higher sodium levels than females.
Those with a high sodium intake were also found to have a 3.4-fold increased chance of developing a new brain lesion on MRI scans, and had eight more T2 lesions on average than patients with the recommended dietary salt intake.
The researchers were able to confirm their findings in a replication study involving 52 patients with relapsing-remitting MS.
However, the authors stressed that their findings show an association between high sodium intake and worsening MS symptoms, but not causation. “We cannot exclude the possibility of reverse causation: individuals with more relapses received more steroids and thus their salt intake and excretion is increased because they have higher disease activity and not the other way around,” they wrote.
They suggested that future clinical trials could determine whether reducing salt intake is helpful for patients with MS.
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