Sodium, Other Dietary Minerals Do Not Up Risk of Multiple Sclerosis

VANCOUVER, BC—Dietary sodium intake is not associated with MS risk in a prospective cohort of women from the Nurses' Health Study and Nurses' Health Study II, a study reported at the 68th AAN Annual Meeting.

In addition, "no clear associations with dietary intake of other minerals and MS risk" was found, said Kassandra L. Munger, ScD, Harvard T.H. Chan School of Public Health, Boston, MA.

Prompted by previous reports that elevated sodium intake is associated with disease activity in MS and experimental animal models of autoimmune encephalomyelitis, the research team sought to determine whether dietary intake of sodium is associated with risk of MS among women enrolled in the two studies.

The secondary objective was to determine whether dietary intake of potassium, magnesium, calcium, phosphorus, or iron is associated with risk of MS, she said.

The 2015 U.S. Dietary Guidelines recommend consumption of less than 2,300mg/day of sodium, whereas the American Heart Association suggests the aim should be no more than 1,500mg/day. However, on average, U.S. adults consume 3,400mg/day of dietary sodium, >75% from processed foods and >40% from 10 foods/groups: breads/rolls, cold cuts/cured meats, pizza, poultry, soups, sandwiches, cheese, pasta dishes, meat dishes, and snacks. Approximately 11% of intake is from salt added during cooking or at the table.

The study assessed intake of different minerals from diet and supplements using data from the Nurses' Health Study, initiated in 1976, and the Nurses' Health Study II, which began in 1989. The nurses are followed biennially with questionnaires that track lifestyle factors such as smoking, physical, activity, weight and diet as well as medical issues. The validated Food Frequency Questionnaire includes 116 to 131 different items over 7 categories.

In the Nurses' Health Study, 79,777 women were included in the diet sub-cohort (diet tracked from 1984–2004), as were 94,441 in the Nurses' Health Study II (diet tracked from 1991–2009).

A total of 479 new cases of MS over 3,072,138 person-years of follow-up were confirmed, Dr. Munger said.

Multivariate analyses were adjusted for age, pack-years of smoking, latitude of residence, ancestry, body mass index at age 18 years, supplemental vitamin D intake, and total caloric intake. Data for both patient cohorts were pooled using fixed-effects models.

Higher dietary intake of sodium at baseline was not associated with MS risk. At baseline, the rate ratio of MS by quintile of sodium intake ranged from 0.79 for the second quintile to 1.12 for the third quintile (P trend = 0.83); the P trend for the cumulative average was 0.78.

When examined by recommended dietary intake, the rate ratio of MS at baseline was 1.00 for <1,500mg/day, 0.73 for 1,500–<2,300mg/day, and 0.88 for ≥2,300mg/day, with a P trend of 0.50.

The rate ratios of MS by quintile of intake were P trend 0.36 for potassium, 0.13 for magnesium, 0.20 for calcium, and 0.98 for phosphorus, and 0.81 for iron. For these minerals, results "did not change using cumulative average intake over follow-up," Dr. Munger concluded.

A recently published case-control study of pediatric MS found no strong association between dietary salt intake and risk of MS onset.

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