Sources of vitamin D
The timing really couldn’t be better. Just as we’ve had our first heat-health warning of the year, we’re bathed in news on the beneficial effects of vitamin D, also known as the sunshine vitamin.
The first study, from the Peninsula Medical School, (part of the Universities of Exeter and Plymouth), has found that vitamin D may help prevent brain tissue from degenerating. The research, which is published in The Archives of Internal Medicine, looked at 858 adults aged 65 or more in 1998 when the study began. They had three tests for cognitive function at the beginning of the study, and again after three and six years. One test assessed their overall cognition (mental processes such as thinking, judging and problem-solving), one looked at attention, and the third looked at the ability to plan, organise and prioritise.
The research found that those people who were severely deficient in vitamin D (with blood levels of 25-hydroxyvitamin D of less than 25 nanomoles per litre) were 60 percent more likely to have a substantial decline in their cognitive ability over the six-year period, than those who had sufficient levels of vitamin D.
We make vitamin D in our bodies, when our skin is exposed to sunlight. This is our main source, although we can also get it from some foods, such as oily fish, eggs, liver, and fortified cereals and spreads, and from supplements. It’s quite difficult to have too much vitamin D. And you can store it in your body, so if you miss a daily dose it’s not a problem.
"At present we don’t know the correct dosage needed to prevent dementia," said Dr David J Llewellyn, who led the trial. "We now need to complete clinical trials to see just how effective vitamin D is at preventing dementia, and at what levels it should be prescribed. Vitamin D supplements may be an important weapon in the fight against dementia, but should not discount the importance of other factors, such as being physically and mentally active, moderate alcohol consumption and eating a healthy balanced diet."
"This large study provides compelling evidence that the sunshine vitamin - vitamin D - could be linked to cognitive impairment," said Professor Clive Ballard, Director of Research at the Alzheimer’s Society. "The key question now is whether vtamin D deficiency causes problems in brain function or if the lifestyle factors are the same for cognitive impairment and vitamin D deficiency."
The second study in the news is also from the Peninsula Medical School, and the University of Cambridge and the University of Michigan. This study covers similar ground, assessing the cognitive function of nearly 2,000 adults aged 65 and over. The research found that as the participants' levels of vitamin D went down, their levels of cognitive impairment went up. Those with the lowest levels were more than twice as likely to have cognitive impairment as those who had optimum levels of the vitamin.
The research points out that as we get older, our ability to make vitamin D from sunlight decreases, so we have to rely more on food and supplements to provide us with this vital vitamin.
Dr Iain Lang, from the Peninsula Medical School, who worked on the study said, "Dementia is a growing problem for health services everywhere, and people who have cognitive impairment are at higher risk of going on to develop dementia. That means identifying ways in which we can reduce levels of dementia is a key challenge for health services."
As well as potentially helping combat cognitive decline, vitamin D is important for bone health, the absorption of calcium and phosphorous and for our immune system. A third set of research, from Finland (a country which has limited sunlight), has found evidence that this vitamin may also affect our likelihood of developing Parkinson’s disease.
Paul Knekt and colleagues at the National Institute for Health and Welfare in Helsinki studied 3,173 Finnish men and women aged from 50 to 79, from 1978 to 1980. None had Parkinson’s disease at the beginning of the study, which was published in the Archives of Neurology, but over the 29-year follow-up period, 50 participants developed the disease. The researchers found that those in the highest quarter for serum vitamin D levels had a 67 percent lower risk of developing Parkinson’s disease than those in the lowest quarter for vitamin D levels.
"This study investigates Vitamin D levels and their relationship to the subsequent development of Parkinson's. Vitamin D has already been shown in previous studies to have some role in the protection of nerve cells," said Dr Kieran Breen, Director of Research at Parkinson’s UK.
"However, further research would be required to find out whether low levels of vitamin D themselves may increase an individual's risk of developing Parkinson's or whether low vitamin D levels could predict against Parkinson's developing later. The study provides further clues about the potential environmental factors that may influence or protect against the progression of Parkinson’s.
"A balanced healthy diet should provide the recommended levels of vitamin D. Further research is required to find out whether taking a dietary supplement, or increased exposure to sunlight, may have an effect on Parkinson’s, and at what stage these would be most beneficial."
First published July 13, 2010
Useful websites
Alzheimer’s Research Trust - www.alzheimers-research.org.uk
Alzheimer’s Society - www.alzheimers.org.uk
Parkinson’s UK - www.parkinsons.org.uk