Summary: Study finds no association between mineral levels or dietary mineral intake and an increased risk of multiple sclerosis.
Some studies have suggested that minerals such as zinc and iron may play a role in how multiple sclerosis (MS) progresses, once people have been diagnosed with it. But little was known about whether zinc, iron and other minerals play a role in the development of the disease. A new study shows no link between dietary intake of several minerals and whether people later develop MS. The study is published in the April 3, 2019, online issue of Neurology. This article will also be published in the April 30 print issue of Neurology which is largely dedicated to null hypothesis studies with negative or inconclusive results. These results have the potential to inform future research efforts and to save study participants from avoidable risks.
“Higher intake of vitamin D has been associated with a lower risk of MS, but our findings show that intake of minerals is not an important determinant of MS risk,” said study author Marianna Cortese, MD, Ph.D., of Harvard T.H. Chan School of Public Health in Boston.
The study involved 80,920 female nurses in the Nurses’ Health Study and 94,511 in the Nurses’ Health Study II. The women were asked via a questionnaire about diet and any supplement use every four years for up to 20 years of follow-up before some of the women developed MS.
The minerals studied were zinc, iron, potassium, magnesium, calcium, phosphorus, manganese and copper.
During the study, 479 of the women developed MS.
The researchers evaluated the women’s intake of the minerals to see if higher intake was tied to a higher or lower risk of MS. No such relationship was found. Researchers looked at mineral intake at the beginning of the study and also cumulative intake before MS onset and found no association.
The results were the same when researchers adjusted for other factors that could affect the risk of MS, such as smoking and taking vitamin D supplements.
“While previous studies have suggested that zinc levels are lower in people with MS and that zinc may produce a more anti-inflammatory immune response in an animal model of MS, these effects may be too subtle within the range of zinc intakes common in the US population to modify MS risk,” Cortese said.
A limitation of the study was that only women were included, and most were white, so the results cannot be directly generalized to men or people of other races.
Funding: The study was supported by the National Multiple Sclerosis Society and the National Institutes of Health.
About this neuroscience research article
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Total intake of different minerals and the risk of multiple sclerosis
Objective To investigate the association between mineral intake (potassium, magnesium, calcium, phosphorus, iron, zinc, manganese, copper) and multiple sclerosis (MS) risk.
Methods In a prospective cohort study, we assessed dietary and supplemental mineral intake by a validated food frequency questionnaire administered every 4 years to 80,920 nurses in the Nurses’ Health Study (1984–2002) and 94,511 in the Nurses’ Health Study II (1991–2007). There were 479 new MS cases during follow-up. We estimated hazard ratios and 95% confidence intervals for the association of energy-adjusted mineral intake with MS risk using Cox regression, adjusting for age, residence latitude at age 15, ancestry, body mass index at age 18, supplemental vitamin D, smoking, and total energy intake.
Results We did not find any association between the minerals and MS risk, either for baseline or cumulative intake during follow-up. The associations were null comparing women with highest to those with lowest intakes in quintiles or deciles and there was no significant trend for higher intakes (ptrend across baseline quintiles: potassium 0.35, magnesium 0.13, calcium 0.22, phosphorus 0.97, iron 0.85, zinc 0.67, manganese 0.48, copper 0.59).
Conclusions Our findings suggest that mineral intake is not an important determinant of MS risk.