Vitamin D may help some Parkinson's patients

Depending on their genes, some Parkinson's patients may be 

able to slow their deterioration by taking vitamin D 

supplements, according to a small study from Japan.

Researchers randomly assigned 114 people with Parkinson's 

disease to take either vitamin D or a placebo every day for a 

year and found the neurologic condition didn't progress as 

much in those who took the supplements, compared to those 

who took placebos. But that was only true for people with 

certain versions of a gene for the vitamin D receptor.

Previous studies have found that people with Parkinson's 

disease have low levels of vitamin D circulating in their 

blood, though none have established whether the vitamin 

deficiency is a cause or effect of the disease.

The body produces vitamin D from sunlight exposure and 

uses it to help get calcium into bones, among other functions. 

The vitamin itself activates a receptor protein in cells that 

triggers the activity of a variety of genes.

For the new study, researchers recruited 114 Parkinson's 

patients between 45 and 85 years old to see whether taking 

vitamin D supplements would change how fast the symptoms 

of Parkinson's disease progressed.

Of those, 56 patients took 1,200 international units of vitamin 

D per day for 12 months, and 58 took placebos for the same 

length of time.

At the beginning of the study, about 45 patients in each group 

scored a 1 or 2 on a five-point scale that measures disability 

from Parkinson's disease. A score of 1 represents the least 

disability, while a 5 is bedridden.

Measures of disability include whether or not a person has 

impaired movement, trouble balancing and can get around on 

their own.

At the end of the year, the researchers found that 16 people 

in the group taking the supplements didn't get worse on the 

five-point scale, compared to 7 people whose symptoms were 

stable in the group taking the placebo.

But when they looked at the patients' vitamin D receptor 

genes, the researchers found that people with the gene 

version known as FokI TT benefited the most from 

supplements, followed by those with the FokI CT variant, 

compared to people in the placebo group. People with the 

FokI CC genotype did not benefit at all.

Research suggests that people with the FokI TT and FokI CT 

variants respond to the additional vitamin D better than those 

with the FokI CC version of the gene.

Just 14 percent of the study participants had the TT gene 

version, while 52 percent had the CT genotype and 34 

percent had the CC version of the gene. Those proportions 

are in keeping with most populations, where between 8 

percent and 18 percent of people have the TT variant, 

according to the researchers, and between 46 percent and 58 

percent of non-Asians have the CT variant.

There were no differences in the starting levels of circulating 

vitamin D among the study participants, and about half began 

with levels considered deficient. All the patients who got the 

supplements more or less doubled the amount of D in their 

bloodstream by the end of the study while the levels in the 

placebo group didn't change.

The large number of participants taking vitamin D whose 

symptoms did not get worse over the course of the year 

suggests that vitamin D supplementation may stabilize "the 

severity of Parkinson's disease in patients with FokI CT and 

TT genotypes for a short period of time.

But there are still unanswered questions. Among them, what 

effect of vitamin D might account for the symptom differences 

seen at the end of the study.

Past research has found the vitamin can improve muscle 

strength and balance in elderly people, for example. So the 

researchers said they cannot be sure whether the patients' 

Parkinson's did not progress in people who took the D 

supplements or their balance just improved.

If we do the same trial by targeting an older generation 

without Parkinson's disease and get the same results, that 

suggests the effect we observed in this study was due to just 

improving balance, said a researcher.

The bottom line is there are so many other factors to take 

into consideration, he said.