A recent study linking adolescent obesity in women with increased risk of developing multiple sclerosis is interesting in its possible connection to a lack of vitamin D, says Dr. Roger Cooke, medical director at Providence Holy Family Hospital's Multiple Sclerosis Center here.

Obese people tend to have lower levels of vitamin D, Cooke says. A lack of vitamin D long has been eyed as a potential risk factor in developing MS, but previously mostly has been associated with a person's lack of exposure to direct sunlight, he says. A lack of vitamin D is one factor that has been commonly associated with the higher incidence of MS in northern latitudes, he says.

The new study was conducted at Harvard Medical School and Harvard School of Public Health and was published in the November 2009 issue of Neurology, the journal of the American Academy of Neurology.

It says that among 238,000 women who participated in two health studies over the course of more than 20 years, those who said they were obese at age 18 were more than twice as likely to develop MS later in life.

"I think it's fascinating information," Cooke says. "Since MS is a multifactorial disease, we're just looking for clues."

Cooke and Dr. Michael Olek, a neurologist and MS specialist at Rockwood Clinic PS here, each say care should be exercised in reaching conclusions about a historical study that relies on the participants' self-assessment of their previous weight. Olek adds that not many of his MS patients are overweight.

"It's always hard to do a retrospective study," Cooke says, but adds that since MS is a mystery in many ways, all such trends should be looked at.

Cooke says that though the study can't be used to draw any definitive conclusions, if it can help identify trends related to MS, it can provide useful information.

No one knows for sure what causes MS, but it's generally considered an autoimmune disease that destroys myelin, a fatty substance that provides a sheath for nerve fibers. People with the disease often suffer from vision problems, varying levels of muscle weakness, and fatigue.

The Harvard researchers who conducted the study say that while the reason for the apparent connection between weight at age 18 and risk of developing MS isn't clear, they suggest there are problems associated with obesity, such as inflammatory processes and lower circulating vitamin D levels, that also are present in patients with MS.

Another possibility suggested by the study is that fatty tissue produces substances that could adversely affect the immune system.

The Harvard study was conducted using women's health records, collected as part of two related nurse's health studies. Those studies followed women who were between the ages of 25 and 55 at the beginning of the study, between 1976 and 2002. Over the course of the study, 593 of the women developed MS.

According to the Harvard studies, participants who identified themselves as being obese at the age of 18 were more than twice as likely to develop MS later. Larger body sizes at ages 5 and 10 years were not associated with MS risk, as long as study subjects were not obese at age 18, the researchers reported. Cooke says that although most people likely won't take steps to deter being obese as teenagers in order to avoid developing MS, the study results could be useful for families that know they have a genetic predisposition to the disease.

Cooke also says that smoking, while not established as a cause of MS, does tend to increase a person's chance of getting MS and of getting worse if they do have it.

Olek says that so far, aside from quitting smoking, the only factor that has seemed to markedly change a person's risk of developing the disease is moving closer to the equator before age 15.

Washington state has one of the highest rates of MS in the country, and is at the highest latitude of any state except Alaska, Cooke says.

One thing people can do is take supplemental vitamin D, Cooke says, adding that he takes 2,000 milligrams a day of vitamin D, and advises his patients to give their children supplements. Cooke says that dosage is quite safe for most people, as long as they don't have certain kidney problems.

He says the study is, if nothing else, a reminder that overall, being in good health in order to maintain a healthy immune system is beneficial.

"Obesity is bad for us in many ways," he says. Still, Cooke says, since there also may be genetic factors involved in obesity, it's unwise to draw too many generalizations from any one study.

MS is a complex health issue and researchers are still trying to understand the disease and what triggers it, Cooke says.

Kerry Wiltzius, program director at the Spokane Chapter of the National Multiple Sclerosis Society, says that for the more than 2,500 members of the society here, different things seem to trigger people's onset of symptoms, including severe stress.

"We're seeing it in a lot of men coming back from war," Wiltzius says.

Cooke says people who have been exposed to the Epstein-Barr virus, which causes mononucleosis, have an increased risk of developing MS later.

"If you've never had (Epstein-Barr), you have an almost zero percent risk of developing MS," Cooke says.