0930 GMT February 24, 2020
But clinical trials are still underway to answer the big question: Does taking vitamin D improve MS symptoms and alter the course of the disease?
The current study shows only that high doses, 10,400 International Unit (IU) a day, reduce the proportion of certain immune-system cells that have been implicated in the MS disease process, Medical Xpress reported.
"I'm not going to make any claims beyond that," said senior researcher Peter Calabresi, a professor of neurology at Johns Hopkins University in Baltimore."We don't have enough data here to guide clinical practice," he stressed.
Bruce Bebo, executive vice president of research for the National Multiple Sclerosis Society, echoed that caution. "This study was not designed to look at efficacy against MS. It was too small and too short to do that," said Bebo, whose group helped fund the research.
Still, Bebo added, the findings are important for other reasons. “For one, they give us some hints about the mechanisms that explain the higher MS risk associated with low vitamin D."
The precise cause of MS is unknown, but researchers believe it involves a combination of genetic vulnerability and certain environmental triggers. Inadequate vitamin D, a nutrient needed for normal immune function, is considered as one of the suspects.
That's partly based on studies showing an association between blood levels of vitamin D and the risk of developing MS. But there is also more-direct evidence, Bebo said. For example, research has shown that vitamin D can reduce the effects of an MS-like disease in lab mice.
The new findings suggest it may alter immune system activity in people with MS, too, Bebo said.
According to Calabresi, the results underscore another point: High doses of vitamin D are probably necessary.
His team tested two doses in 40 adults with MS. Over six months, one group took 10,400 IU of vitamin D a day, about 17 times the amount that the US government recommends for healthy adults (600 IU a day); the other group took 800 IU a day.
In the end, only the high-dose group showed changes in their immune system activity. The largest effect, Calabresi said, was a reduction in cells that produce an inflammatory protein called ‘interleukin-17’.