A little ray of sunshine for Parkinson’s disease may lie with Vitamin D.
Vitamin D is the vitamin we obtain through the action of ultraviolet light on our skin. Most of the vitamin D produced is then bound in the blood and only a tiny fraction remains free and able to bind to specific vitamin D receptors now known to be located in a number of target organs in the body including the brain.
Not only that, but the area of the brain with the highest density of Vitamin D receptors is in the Substantia Nigra. This is where highly specialized cells produce Dopamine, the brain neurotransmitter vital for regulating our mood, concentration, motivation and voluntary movement. In Parkinson’s disease many of these highly specialized cells die and the loss of Dopamine manifests itself in the form of tremor, rigidity of movement, slowness of gait and cognitive decline. Plus, thirty percent of people with Parkinson’s disease develop dementia. It is the second most common neurodegenerative disease in Australia and remains one of the most poorly understood.
So where does Vitamin D fit in with Parkinson’s disease?
The answer to that is not yet certain, but a recently published study has linked having a higher level of Vitamin D with up to a 65% reduction in the risk of developing Parkinson’s.
These results were in a long prospective study by Paul Knekt in Finland. He showed that in a group of 3173 people aged 50 to 79, followed up over a 29 year period, those with a higher level of Vitamin D had a 65% lower risk of developing Parkinson’s compared to those with the lowest levels.
However it should be noted that all of the subjects in this study actually had lower levels of vitamin D than is recommended. This may reflect the fact that Finland is not a country associated with a lot of sun exposure for its residents. So the suggestion is that having a lower level of Vitamin D may be a predisposing factor to an increased risk of Parkinson’s disease. There is no suggestion that having a low level is in fact a cause. The study remains a starting point to determine whether giving Vitamin D as a supplement would be useful.
One of the problems recognized is that Vitamin D deficiency is widespread, even in a sunny country such as Australia. It has been reported that half to two thirds of teenagers and adults in the US have lower than desirable levels. Because it is very difficult to get sufficient Vitamin D through our diet, having adequate sun exposure is essential to help us achieve and maintain a healthy level.
How much time do we need in the sun?
Five to fifteen minutes of sunlight exposure to the face and upper arms, four to six times a week is thought to be sufficient to prevent deficiency. Those particularly at risk of deficiency here in Australia include the elderly living in residential care and dark skinned women, especially those who are veiled. The use of sunscreen (essential to protect us from skin cancer) unfortunately prevents the synthesis of Vitamin D in the skin. Application of Factor 8 will prevent up to 95% of Vit D conversion, so a short exposure without sunscreen is recommended and outside the high-risk times of 10 am to 3 pm.
Can we get Vitamin D from our food?
We can derive a limited amount of Vitamin D from food sources. However in cases of deficiency taking a supplement would be recommended.
Vitamin D2 can be found in:
Fatty fish such as mackerel, salmon and herring Fortified margarines Cod liver oil Liver Eggs
The role of Vitamin D in the brain
The association of Vitamin D and Parkinson’s disease is intriguing and as yet not fully explained. It is believed that Vitamin D acts as a hormone rather than a vitamin, in addition to its role in bone metabolism.
Current thinking is that it may exert a neuroprotective effect through its antioxidant properties, calcium regulation of nerve cells, enhanced nerve conduction, detoxification and immunomodulation.
A UK study looked at Vitamin D levels of a group of 858 Italian men and women over the age of 65 years. Of those with dementia, 50% were vitamin D deficient. Moreover, those with the greatest deficiency had a 60% increased risk of suffering cognitive decline over the 6-year follow up period.
The role of Vitamin D relating to Alzheimer’s disease was looked at in a 2008 study where 100 people with Parkinson’s disease were compared to 100 subjects with Alzheimer’s disease and 100 healthy controls. Here the fraction of patients with the lowest levels of Vitamin D was most marked in the Parkinson’s group (23%) compared to the Alzheimer’s group (16%) and healthy group (10%) indicating support for the notion that Vitamin D plays a role in affording some neuroprotection.
Meanwhile it remains prudent to ensure that we obtain adequate sun exposure to keep our Vitamin D levels up. So go on, it’s time to enjoy some time in the sun.
References: Emory University (2008, October 17). Lack Of Vitamin D Linked To Parkinson's Disease. Archives of Neurology  67 (7) : 808-811 (Knekt P, Kilkkinen A, Rissanen H, Marniemi J, Sääksjärvi K, Heliövaara M.)