Risk of MS among women drops by over 40% with greater vitamin D intake
New Norway study finds lower risk independent of sun exposure
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- Higher vitamin D intake significantly lowers multiple sclerosis risk among women, a study from Norway found.
- This protective effect is independent of sun exposure, which suggests vitamin D itself is key.
- Increasing vitamin D through diet and supplements is a safe, cost-effective prevention, the researchers noted.
A greater intake of vitamin D, from both food and supplements, was linked to a 42% lower risk of developing multiple sclerosis (MS) among women living in Norway, according to a large prospective study.
“Our findings suggest that a higher dietary intake of vitamin D decreases the risk of developing MS,” the researchers wrote, noting that the study was conducted in a Nordic country where people produce insufficient vitamin D from sun exposure most of the year.
“The risk estimates were similar whether vitamin D came from food or supplements,” the team noted.
The results also supported the researchers’ hypothesis that vitamin D itself, rather than sunlight alone, modifies MS risk, according to the team.
The study, “Vitamin D intake and multiple sclerosis risk in the Norwegian Mother, Father and Child cohort,” was published in the Journal of Neurology, Neurosurgery and Psychiatry.
Vitamin D, best known for its role in maintaining bone health, also plays a crucial role in regulating the immune system and supporting brain and muscle health.
The body usually produces vitamin D when the skin is exposed to sunlight. But people living at northern latitudes have limited sun exposure, so they often rely more heavily on diet and supplements to maintain adequate levels.
Foods high in vitamin D include fatty fish such as salmon and tuna, as well as beef liver and egg yolks. Many foods, such as milk, yogurt, orange juice, and cereals, are also fortified with vitamin D to give them an extra boost.
Investigating vitamin D intake vs. sun exposure
Greater intake of vitamin D and higher blood levels of the vitamin have consistently been linked to a lower risk of MS. The neurological disease is marked by immune-mediated damage to the brain and spinal cord, but much still remains unknown as to its causes and risk factors.
For one, the researchers noted, “some controversy remains with regard to whether it is vitamin D modifying the disease risk or whether sunlight is the key protective factor and vitamin D is merely a marker of sun exposure.”
To help resolve this controversy, a team from the University of Bergen conducted a large prospective study focused on people living in the northern European country. Because Norway has limited sunlight exposure for much of the year, it provides a unique setting to examine the effects of dietary vitamin D independent of sun exposure, the researchers noted.
The team used data from 78,074 pregnant women who entered the Norwegian Mother, Father and Child Cohort Study (MoBa) between 2002 and 2008. MoBA is a nationwide population-based study that aims to investigate the causes of serious diseases.
All had completed a validated food-frequency questionnaire designed to capture their usual food intake, dietary habits, and supplement use during the first half of pregnancy. This allowed researchers to estimate each woman’s daily vitamin D intake at the start of the study. The women were then followed through 2022.
Based on data from the Norwegian MS Registry, which encompasses all patients with MS in Norway, a total of 349 women (0.5%) developed MS over a median follow-up period of 17 years.
Researchers note safety, cost-effectiveness of supplements
Among the women who had developed MS, the median total daily vitamin D intake — combining both food and supplements — was 296 international units (IU). That compared with 333 IU among women who did not develop MS.
Similar trends were seen when vitamin D sources were examined separately. Women who developed MS showed lower vitamin D intake from both food (114 vs. 127 IU) and supplements (166 vs. 200 IU) than those who did not.
Vitamin D intake tended to be higher among women aged 35 and older and among those with a lower prepregnancy body mass index or BMI, which is a measure of body fat calculated from a person’s height and weight.
Statistical analyses then showed that higher intake of total vitamin D was linked to a 42% lower risk of developing MS compared with lower intake. This association remained significant even after adjusting for age at delivery, total energy intake, prepregnancy BMI, smoking, and education.
This [study] supports the hypothesis that vitamin D itself modifies MS risk.
Vitamin D intake from both food sources and supplements also independently showed similar protective trends.
“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,” the researchers wrote. “This supports the hypothesis that vitamin D itself modifies MS risk.”
The team noted that vitamin D decificiency is a problem worldwide, not just in countries at higher latitudes.
Given that, “the identification that vitamin D may be a protective factor for MS may hold significant implications for public health,” the researchers wrote. “Moreover, the safety and cost-effectiveness of vitamin D supplementation amplifies the significance of these findings.”
