Higher vitamin D intake is linked to a 42 per cent lower risk of multiple sclerosis, independent of sun exposure, new research suggests.
The findings support the hypothesis that vitamin D itself modifies MS risk, rather than simply acting as a marker of sun exposure.
Greater intake of vitamin D and higher blood levels of the vitamin have consistently been linked to a lower risk of MS, a neurological disease where the immune system damages the brain and spinal cord.
However, some controversy has remained as to whether it is vitamin D modifying the disease risk or whether sunlight is the key protective factor.
To help resolve this, a team from the University of Bergen in Norway conducted a large prospective study.
Because Norway has limited sunlight for much of the year, it provides a useful setting to examine dietary vitamin D independent of sun exposure.
The team used data from 78,074 pregnant women who entered the Norwegian Mother, Father and Child Cohort Study between 2002 and 2008.
All completed a validated food frequency questionnaire capturing usual food intake, dietary habits and supplement use during the first half of pregnancy. The women were then followed through 2022.
Based on data from the Norwegian MS Registry, a total of 349 women developed MS over a median follow-up of 17 years.
Among those who developed MS, the median total daily vitamin D intake (food plus supplements) was 296 international units, compared with 333 international units among women who did not develop MS.
Similar trends were seen when vitamin D sources were examined separately, with lower intake from both food and supplements among women who developed MS.
Statistical analyses showed that higher total vitamin D intake was linked to a 42 per cent lower risk of developing MS compared with lower intake.
This association remained significant after adjusting for age at delivery, total energy intake, pre-pregnancy body mass index, smoking and education.
The researchers wrote: “In this prospective study, higher vitamin D intake was associated with lower MS risk in women living in Norway, where there is insufficient sun-induced vitamin D production during most of the year.
“This supports the hypothesis that vitamin D itself modifies MS risk.”
They noted that vitamin D deficiency is a problem worldwide, not just in countries at higher latitudes.
The researchers added: “The identification that vitamin D may be a protective factor for MS may hold significant implications for public health.
“Moreover, the safety and cost-effectiveness of vitamin D supplementation amplifies the significance of these findings.”
