Behind the headlines: Is Parkinson's disease linked to low vitamin D?

People with Parkinson's disease are more likely to have insufficient levels of vitamin D than healthy people of the same age, according to media reports.

A study published in the Archives of Neurology compared vitamin D levels of 100 people with Parkinson's disease with those of healthy elderly people. The body is able to produce vitamin D using ultraviolet radiation from the sun and most vitamin D in the body is obtained this way because only a few foods contain substantial amounts.

A potential link for vitamin D in the development of Parkinson's disease has been suggested on the basis of studies showing that it is involved in a number of processes impaired in patients.

Vitamin D levels have been found to be lower in Parkinson's sufferers

What is the research?
Dr Marian Evatt and colleagues from Emory University, Georgia, US, assessed vitamin D concentrations from 100 people with Parkinson's disease and compared them with those of 99 healthy controls. Vitamin D levels were assessed by measuring levels of plasma 25-hydroxyvitamin D (25(OH)D), the form in which the vitamin is stored.

A statistically higher proportion of those with Parkinson's disease had insufficient levels of vitamin D compared with healthy controls: 55 per cent of those with Parkinson's, compared with 36 per cent of healthy controls.

Dr Evatt and her colleagues say that further studies are needed to determine factors contributing to the differences and to clarify the potential role of vitamin D in the pathogenesis and clinical course of the disease.

What do the researchers say?
'These findings support the previously suggested need for further studies to assess what contribution a low 25(OH)D concentration adds to the risk of developing Parkinson's disease,' Dr Evatt and colleagues say in their paper. Studies should also assess whether correcting low vitamin D will improve motor or non-motor symptoms in Parkinson's disease.

They point out that the higher prevalence of vitamin D insufficiency in people with Parkinson's disease is not unexpected, since the symptoms associated with Parkinson's disease are likely to lead to patients with the disease having decreased activity levels and lower sunshine exposure, compared with healthy people of the same age.

They add: 'The finding of a high incidence of vitamin D deficiency in the Parkinson's disease highlights the importance of routinely checking the level of 25(OH)D, particularly in elderly patients, since deficiency is strongly correlated with a higher incidence of osteoporosis, falls, and hip fractures and has been associated with a higher incidence of several forms of cancer and autoimmune disorders.'

What do other researchers say?
Dr Kieran Breen, director of research at the Parkinson's Disease Society said that studies of this sort provide clues as to what happens to the brains of people living with Parkinson's.

'Further research is required to determine at what stage the deficiency in vitamin levels occur in the brains of people with Parkinson's and whether the provision of a dietary supplement, or increased exposure to sunlight may help alleviate symptoms or have an effect on the rate of the condition's progression,' he said.

'This would help us answer the question as to whether the decrease in vitamin D levels in Parkinson's is a cause or an effect of the condition.'

tom.moberly@haymarket.com

Informing patients

  • People with Parkinson's disease have lower than normal levels of vitamin D.
  • Further studies are needed to shed light on the cause and effect relationship of this link.
  • Elderly patients' vitamin D levels should be regularly checked.

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