Sixteen percent of 25 people with multiple sclerosis (MS) given an average of 14,000 international units (IU) of vitamin D a day for a year suffered relapses, says Jodie Burton, MD, a neurologist at the University of Toronto. In contrast, close to 40% of 24 MS patients who took an average of 1,000 IU a day -- the amount recommended by many MS specialists -- relapsed, she says.
Also, people taking high-dose vitamin D suffered 41% fewer relapses than the year before the study began, compared with 17% of those taking typical doses.
People taking high doses of vitamin D did not suffer any significant side effects, Burton tells WebMD.
The findings were presented at the annual meeting of the American Academy of Neurology.
In contrast to many vitamins, no recommended dietary allowance (RDA) has been established for vitamin D. Instead, the Institute of Medicine has set a so-called adequate intake level; the recommendations are 200 IU daily for people under 50, 400 IU daily for people 50 to 70, and 600 IU for those over 70.
John Hooge, MD, an MS specialist at the University of British Columbia in Vancouver who was not involved with the research, says he recommends MS patients take at least 1,000 IU and "probably 2,000 IU" day.
"This is an impressive study that shows that even higher doses are probably safe and even more effective. Maybe next year, I'll be recommending higher doses," he tells WebMD.
Vitamin D vs. Relapsing MS
Most of the people in the study had the relapsing form of MS, characterized by repeated relapses with periods of recovery in between. They suffered from the disease for an average of eight years.
"They had very mild disease, with an average score of 1.25 on the Extended Disability Status Scale, where zero corresponds to normal and 10 to death," Burton says. Participants suffered one relapse every other year, an average.
People in the high-dose group were given escalating doses of vitamin D in the form of a concentrate that could be added to juice for six months, to a maximum of 40,000 IU daily. Then doses were gradually lowered over the next six months, averaging out to 14,000 IU daily for the year.
The rest of the participants were allowed to take as much vitamin D as they and their doctors thought was warranted, but it averaged out to only 1,000 IU daily.
Vitamin D appears to suppress the autoimmune responses thought to cause MS, Burton says. In MS, haywire T lymphocytes -- the cellular "generals" of the immune system -- order attacks on the myelin sheaths that surround and protect the brain cells.
In people given high-dose vitamin D in the study, T cell activity dropped significantly. That didn't happen in people who took lower doses.
The researchers also measured the concentration of 25-hydroxyvitamin D [25(OH)D], also known as calcidiol, in the blood. The Institute of Medicine says that is the best indicator of a person's vitamin D status.
There's no ideal level, although concentrations of less than 50 nanomoles per liter of blood are considered inadequate for good health. In the study, it appeared MS patients did best if levels reached 100 nanomoles per liter, Burton says.
People with MS should talk to their doctors about whether they might benefit from vitamin D supplements, she says.
"Too much vitamin D can be harmful for people with certain medical conditions such as kidney disease," Burton says. "Also doctors can monitor your blood levels of 25(OH)D."