Elevated Salt and Mineral Intake Not Linked to Higher Risk of Multiple Sclerosis

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The role of sodium and other minerals as risk factors for MS was previously unclear.
The role of sodium and other minerals as risk factors for MS was previously unclear.

VANCOUVER, British Columbia — Research presented at the 68th annual meeting of the American Academy of Neurology (AAN) has found that neither salt intake nor the intake of certain other minerals increases the risk for developing multiple sclerosis (MS).

According to Marianna Cortese, MD, from Bergen, Norway, and colleagues, “higher dietary sodium intake has been associated with more severe disease activity both in experimental autoimmune encephalomyelitis (EAE) and in patients with multiple sclerosis (MS). However, the role of sodium and other minerals as risk factors for MS is unclear.”

“A high-salt diet worsens EAE, a murine MS model involving interleukin-17-producing helper T-cells, which in turn can be activated in vitro with high salt concentrations,” wrote Kathryn Fitzgerald, PhD, postdoctoral research fellow from the School of Public Health at Harvard University in Boston, Massachusetts, and colleagues. “The only human study relating salt intake to MS activity used a single urine sample, which does not adequately reflect long-term salt intake.”

To study whether an increased dietary intake of sodium, potassium, magnesium, calcium, phosphorus, or iron affects the risk of MS, Dr Cortese and colleagues prospectively analyzed the intake of minerals from diet and supplements in validated food frequency questionnaires administered every 4 years to 81 757 nurses from the Nurses' Health Study (NHS) between 1984 and 2004, and to 95 452 nurses from the Nurses' Health Study II between 1991 and 2009. Analyses were adjusted for age, latitude of residence at age 15, ethnic background, body mass index at age 18, supplemental vitamin D intake, cigarette smoking, and total energy intake. There were 479 new MS cases confirmed in follow-up.

Dr Cortese and colleagues found that higher intake of sodium at baseline was not associated with MS risk (highest [median 2.2 g/d NHS; 2.6 g/d NHSII] vs lowest [median 1.4 g/d NHS; 1.7 g/d NHSII] quintile: HRpooled=0.95, 95% confidence interval [CI], 0.72-1.27, P =.84 [for trend]). In addition, intake of potassium (P=.38 [for trend]), magnesium (0.12), calcium (0.21), phosphorus, (0.99) or iron (0.81) was not associated with risk of developing MS.

“Our findings suggest that neither higher dietary sodium intake nor intake of the other investigated minerals is related to the risk of developing MS,” Dr Cortese and colleagues wrote.

Dr Fitzgerald and colleagues studied whether a diet high in salt, as assessed by measuring the concentration of sodium in urine, was associated with a faster conversion from clinically isolated syndrome (CIS) to MS, as well as MS activity and progression.

The researchers conducted the BENEFIT trial, in which they compared early vs delayed interferon beta-1b treatment in 465 participants with a first event suggestive of MS (CIS). Every participant provided a median of 14 (IQR: 13 to 16) spot urine samples semi-annually[LS1]  throughout the 5 years of follow-up.

The researchers found that average 24-hour sodium levels were not associated with the conversion to clinically definite MS over the 5-year follow-up (hazard ratio [HR]=0.92; 95% CI, 0.78-1.09 per 1000-mg increase in estimated daily sodium intake). Average 24-hour sodium levels were also not associated with clinical or MRI outcomes (new active lesions after 12 months HR: 0.98; 95% CI, 0.94-1.03; relative change in T2 lesion volume: -0.08; 95% CI, -0.23-0.05; change in EDSS: 0.02; 95% CI, -0.03-0.06; time to first relapse HR: 0.91; 95% CI, 0.77-1.08).

“Our results, based on multiple assessments of sodium excretion over 5 years and standardized clinical and MRI follow-up, suggest that salt intake does not influence MS disease course or activity,” wrote Dr Fitzgerald and colleagues.

Disclosures

M. Cortese: None. T. Chitnis: Novartis, Merck-Serono, Biogen. A. Ascherio: Bayer HealthCare. K. Munger: None.

See the abstract online for a full list of disclosures from the study conducted by Dr Fitzgerald and colleagues.

Click here for more coverage from the 68th Annual Meeting of the American Academy of Neurology, April 15-21, 2016, in Vancouver, British Columbia, Canada.

References

  1. Cortese M, Chitnis T, Ascherio A, Munger K. Dietary intake of sodium and other minerals and the risk of multiple sclerosis. Presented at: The 68th Annual Meeting of the American Academy of Neurology. April 15-21, 2016; Vancouver, British Columbia, Canada. Presentation S37.001.
  2. Fitzgerald K, Munger K, Freedman M, et al. Increased sodium intake is not associated with ms activity or progression in BENEFIT. Presented at: The 68th Annual Meeting of the American Academy of Neurology. April 15-21, 2016; Vancouver, British Columbia, Canada. Presentation S37.002.
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