A high intake of dietary salt may worsen symptoms of multiple sclerosis (MS), and increase the risk of further neurological deterioration.

Previous research has found that dietary salt may modify the automimmune response, which is associated with the onset of MS. However, it is not clear if salt plays any direct role in the cause of the disease itself.

MS is an often disabling disease of the central nervous system that interrupts information flow within the brain, and between the brain and body. The cause of MS is still unknown – researchers believe that it may be triggered by unidentified environmental factors in a person who may be genetically predisposed to respond to such factors.

In an observational study published online in the Journal of Neurology Neurosurgery & Psychiatry, researchers analyzed urine and blood samples taken from 70 individuals with the relapsing-remitting type of MS to identify specific levels of salt; vitamin D, with low levels previously linked to the disease; and creatinine, a marker of inflammatory activity.

The participants were tracked over a nine month period where further urine samples were provided, and any changes in salt intake were monitored. A second group was also measured for urinary salt levels, and involved 52 people with the same form of MS.

In both groups, salt intake averaged approximately 4g daily.

After taking into account other factors such as age, gender, smoking, weight and circulating vitamin D, the research indicated that a high level of salt intake was associated with aggravated symptoms of MS.