Sodium Intake Ruled Out as Cause of Multiple Sclerosis

A recent report found there’s no link between dietary sodium intake and the risk for multiple sclerosis (MS).

Researchers from the Harvard T.H. Chan School of Public Health evaluated food frequency questionnaires in order to prospectively examine the link between sodium intake and MS risk. The surveys were administered every 4 years to about 80,000 nurses in the Nurses’ Health Study (between 1984 and 2002) and about 94,000 nurses in the Nurses’ Health Study II (between 1991 and 2007).

The questionnaires asked about different exposures, such as lifestyle and health-related outcomes, as well as dietary sodium intake, and assessed portion size and usual consumption of 130 food items in categories such as: dairy products, fruits, vegetables, breads/cereals/starches, eggs/meats, beverages, sweets/baked goods, and miscellaneous.

The team then followed up with the neurologists of the women who reported an MS diagnosis in their questionnaire and additionally reviewed their medical records.

Marianna Cortese, MD, Harvard T.H. Chan School of Public Health, explained to MD Magazine that many papers suggested a link between sodium or salt and development of MS. These papers purported it was possible that the increase in salt intake in the past few decades could be the explanation behind the perceived increase of MS occurrence.

Women with a higher sodium intake had a higher body mass index on average at age 18 and a lower vitamin D supplementation at baseline and also reported more years spent smoking.

Overall, there were 479 incident cases of MS in the follow up years of the study: 70% had relapsing remitting MS, 15% had progressive MS (either primary or secondary), and 15% had an unknown or other disease course.

There was no link between sodium intake and the risk of developing MS, the researchers reported, after analyzing various intake levels via the patient surveys. Additionally, the researchers believe that reducing the dietary intake of sodium is unlikely to reduce the risk of developing MS.

“This study will not directly affect how doctors treat their patients, but is important for the understanding of MS pathogenesis,” Dr. Cortese told MD Magazine. “Sodium intake might not play an important role in MS, but of course salt intake should be moderated with regard to cardiovascular health.”

While many studies observing the possible link between sodium intake and MS development in animal models seem to show an association, this was not observed in this study. The researchers attributed this possibly to sodium dosages used in animal models of experimental allergic encephalomyelitis (EAE), which far exceeds the typical human intake, and could accelerate EAE onset.

Instead, these findings concurred with a pediatric case that examined salt and MS development, which didn’t find an association, the study authors wrote. They added it could be that sodium plays no role in MS onset, or that it only interacts in those patients with a genetic predisposition.

The paper, titled “No association between dietary sodium intake and the risk of multiple sclerosis,” was published in the journal Neurology.