Salt Intake May Worsen Multiple Sclerosis Symptoms

If you have multiple sclerosis (MS), you might feel better, and fare better in the long run, if you cut salty foods from your diet.

Multiple sclerosis is a chronic condition in which the patientís immune system attacks the nervous systemóthe brain, spine, and optic nerves. The immune system damages nerves and myelin, the fatty substance that protects nerve fibers. It affects an estimated 400,000 people in the U.S.

Why would salt intake have an effect on MS symptoms? Salt increases the number of a specific type of immune cells associated with autoimmune diseases (like MS), resulting in increased inflammation. Basically, anything that affects the immune system can trigger MS symptoms, according to David Hafler, MD, MSc, Professor of Neurobiology and Immunobiology and Chairman of the Department of Neurology at Yale School of Medicine and Neurologist-in-Chief at Yale New Haven Hospital.

Research on Salt and MS Symptoms

In early lab studies, researchers found that mice engineered to have MS and fed a high sodium (salt) diet had worse symptoms than mice with MS who ate more moderate amounts of salt. And a recent study in the Journal of Neurology, Neurosurgery & Psychiatry found that too much dietary salt also has a negative effect on MS symptoms in humans: Researchers discovered that the MS symptoms of patients eating moderate amounts (2,000-4,800 mg. a day, according to Medical News Today) of sodium were almost three times as aggressive as those on a low sodium (under 2,000 mg.) diet. And the symptoms of patients with a high sodium intake (4,800 mg. or more) were five times worse than those of patients with low sodium intake.

MRI (magnetic resonance imaging, an imaging technique) reports also revealed that those patients with high sodium intake had more than four times the chance of developing more brain and spinal cord lesions (or plaques), which are the result of the inflammation that causes the immune system to attack myelin. These patients also had an average of eight more lesions than those on a low sodium diet.

Moving Forward

Hafler and his team are currently conducting a study of the effects of dietary salt on the immune systems of patients newly diagnosed with MS, as well as on healthy individuals. If they find a connection, they will go on to investigate whether this relationship is specific to those with MS or also affects the general population. They will then test to see if a sodium-restricted diet can help restore immunity.

What You Can Do

"We donít know yet how much salt is too much and how low to go to have an effect on MS symptoms," Hafler says. "But since the disease may take a more aggressive toll on patients who consume too much, itís probably wise to check the sodium levels in any processed foods before you buy them, and cut back on added salt at the table and in cooking."

The Dietary Guidelines for Americans, 2010 recommends that most Americans consume no more than 2,300 mg. of salt a day. People 51 and older, as well as African Americans and anyone with high blood pressure, diabetes, or chronic kidney disease, should limit their salt intake to no more than 1,500 mg. a day. (The Guidelines also estimate that Americans ages 2 years and up consume significantly more salt than recommendedóan average of 3,400 mg. a day.)

Foods to Watch out For

Canned soups, luncheon meats or cold cuts, snack foods, and other processed foods are all especially high in sodium. According to government definition, a low-sodium product is any food that contains 140 mg. or less per serving. Use that figure as a guide when reading and comparing the Nutrition Facts information on food labels. In home cooking, cut back on or eliminate added salt and, instead, flavor foods with herbs, spices, lemon juice, flavored vinegars and seasoning vegetables such as garlic and onions.

David Hafler, MD, MSc, reviewed this article.

Sources

Hafler, David. Phone call to author, March 1, 2015; email to author, March 3, 2015.

Farez MF, Fiol MP, Gaitan MI, Quintana FJ, Correale J. "Sodium Intake Is Associated With Increased Disease Activity in Multiple Sclerosis." J Neurol Neurosurg Psychiatry 2015 86:26-31. doi: 10.1136/jnnp-2014-307928

"Too Much Salt May Heighten MS Symptoms." Medical News Today. Last updated August 29, 2014.

"Frequently Asked Questions About Multiple Sclerosis." Multiple Sclerosis Association of America. Page accessed March 5, 2015.

"Multiple Sclerosis: Hope Through Research." National Institute of Neurological Disorders and Stroke. Published June 2012, last updated March 3, 2015.

Kleinewietfeld M., et al. "Sodium Chloride Drives Autoimmune Disease by the Induction of Pathogenic TH17 Cells." Nature 2013 496(7446): 518-522. doi:10.1038/nature11868