Vitamin D shortage linked to Parkinson's
People with low vitamin D levels could be more susceptible to Parkinson's disease
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Tuesday, 14, Oct 2008 08:20
People with low vitamin D levels could be more susceptible to Parkinson's disease, a study showed today.
American researchers uncovered a link between Parkinson's sufferers and a lack of the vitamin.
Fifty-five per cent of patients involved in the Emory University school of medicine trial had both the neurodegenerative disease and insufficient levels of vitamin D, compared to 41 per cent of Alzheimer's sufferers and 36 per cent of healthy elderly people.
The finding adds to evidence that low vitamin D is associated with Parkinson's, says first author Marian Evatt, assistant professor of neurology at Emory.
Dr Evatt and her team, publishing their findings in the October issue Archives of Neurology, compared Parkinson's patients to Alzheimer's patients because they wanted to evaluate the possibility that neurodegenerative diseases in general lead to vitamin D insufficiency.
Most people get the majority of their vitamin D from exposure to sunlight or by dietary supplements; fortified foods such as milk and packaged cereals are a minor source. Only a few foods in nature contain substantial amounts of vitamin D, such as salmon and tuna.
The body's ability to produce vitamin D using UV-B radiation from the sun decreases with age, making older individuals at increased risk of vitamin D deficiency.
"We found that vitamin D insufficiency may have a unique association with Parkinson's, which is intriguing and warrants further investigation," Dr Evatt says.
The connection could come partly because patients with Parkinson's have mobility problems and are seldom exposed to the sun, or because low vitamin D levels are in some way related to the genesis or progression of the disease.
Dr Evatt said her team saw their results as striking because their study group came from south-east US, not a region with long gloomy winters, where vitamin D insufficiency is thought to be more of a problem.
In addition, the study found the fraction of patients with the lowest levels of vitamin D, described as vitamin D deficiency, was higher (23 per cent) in the Parkinson's group than the Alzheimer's group (16 per cent) or the healthy group (ten per cent).
Vitamin D insufficiency is frequently defined as less than 30 nanograms per millilitre of blood of the 25-hydroxy form (the major storage form) of the vitamin and deficiency as less than 20 nanograms per millilitre. However, most experts agree insufficiency warrants treatment and should not be ignored.
Doctors have known for decades that vitamin D plays a role in bone formation, Dr Evatt said. More recently, scientists have been uncovering its effects elsewhere, including producing peptides that fight microbes in the skin, regulating blood pressure and insulin levels, and maintaining the nervous system. Low vitamin D levels also appear to increase the risk of several cancers and auto-immune diseases such as multiple sclerosis and diabetes.
Parkinson's disease affects nerve cells in several parts of the brain, particularly those that use the chemical messenger dopamine to control movement. The most common symptoms are tremors, stiffness and slowness of movement. These can be treated with oral replacement of dopamine.
Previous studies have shown that the part of the brain affected most by Parkinson's, the substantia nigra, has high levels of the vitamin D receptor, which suggests vitamin D may be important for normal functions of these cells, Dr Evatt said.
Emory clinicians are conducting further research to investigate whether vitamin D insufficiency is a cause or possibly a result of having Parkinson's. In a pilot study, Parkinson's patients are receiving either standard or larger doses of vitamin D, with an eye towards possibly reducing the severity of their condition.