Lack of Standardized Vitamin D Data Hampers Efforts to Determine Its Role in Parkinson’s, Review Study Says

Low vitamin D serum levels have been associated with Parkinson’s disease, but the lack of standardized data makes it difficult to determine vitamin D’s exact role in Parkinson’s pathology, according to a recent review article.

The study, “Standardized measurement of circulating vitamin D [25(OH)D] and its putative role as a serum biomarker in Alzheimer’s disease and Parkinson’s disease,” was published in Clinica Chimica Acta.

Vitamin D is essential to maintain homeostasis of the musculoskeletal system, and exists in two forms: 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. The major form found in the blood is 25-hydroxyvitamin D, and as such, testing usually quantifies these levels to monitor vitamin D status in individuals.

Low serum vitamin D levels have been associated with Parkinson’s disease, suggesting that elevated vitamin D levels could protect against this neurodegenerative disorder.

In 2010, researchers analyzed the blood concentrations of vitamin D in 3,173 men and women, 50–79 years old, and found that those with higher levels were less likely to develop Parkinson’s. Standardized techniques were used to measure these levels, which revealed that 50 out of the 3,173 people developed Parkinson’s, which is a relatively small number for scientists to draw conclusions on the “protective power” of vitamin D.

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In another study, 25-hydroxyvitamin D blood concentration was found to be significantly associated with motor severity in 145 Parkinson’s patients who were followed for three years. These findings were further supported by two recent meta-analyses evaluating a total of 4,199 patients. Results revealed that serum vitamin D levels were inversely associated with Parkinson’s risk and severity, and that vitamin D supplementation did not improve subjects’ motor function. However, the methods used to quantify vitamin D levels varied between the studies included in the combined statistical analyses.

In an attempt to standardize vitamin D measurements, researchers in the current study reviewed the performance of 25-hydroxyvitamin D assays over the last three decades. So far, “only a few studies evaluating relatively small samples reported standardized data,” the researchers wrote.

“Literature studies in the field of vitamin D mainly report unstandardized results, which hampers the development of consensus guidelines defining optimal vitamin D status,” they said, adding that current data do not support the usefulness of vitamin D as a biomarker for Parkinson’s disease and that further studies “using internationally recognized measurement procedures and materials are required.”