The study – published in the journal Neurobiology of Ageing – revealed that vitamin D3 reduced the effects of ageing in mouse eyes, and suggested that the improvements could significantly help functioning and vision older mice. The researcher team, from the Institute of Ophthalmology at University College London (UCL), UK, said they hope the findings may mean vitamin D supplements could provide a simple and effective way to combat age-related eye diseases, such as macular degeneration (AMD).
“These results clearly demonstrate that vitamin D3 has a marked impact on aged eyes even when given for short periods,” said the researchers – led by Professor Glen Jeffery of UCL.
However in an analysis of the study, the UK NHS choices service said the study has “limited relevance to humans” because it did not specifically look at a mouse model of AMD. Based on the study’s results along, it is therefore not possible to say whether vitamin D has any effect on age-related vision loss or AMD in humans, it warned.
“It is far too early to say whether this vitamin D could prevent AMD as there have not yet been trials in humans,” it added.
Jeffery noted that researchers would need to run full clinical trials in humans “before we can say confidently that older people should start taking vitamin D supplements.”
“But there is growing evidence that many of us in the Western world are deficient in vitamin D and this could be having significant health implications," affirmed Jeffery.
Jeffery explained that the retina requires proportionally more energy than any other tissue in the body, meaning that it requires a good supply of blood.
“With ageing the high energy demand produces debris and there is progressive inflammation,” noted Jeffery. “In humans this can result in a decline of up to 30% in the numbers of light receptive cells in the eye by the time we are 70 and so lead to poorer vision."
However, previous research has suggested that vitamin D3 can delay such age-related changes in metabolism and inflammation. As a result, the research team investigated whether vitamin D3 could influence retinal inflammation, cellular deposition, and retinal function in an aged mouse eye.
The new study analysed the effect of a six weeks course of vitamin D3 injections (in safflower oil) on age-related changes to the eyes of seven mice, compared to a control group if seven mice (receiving safflower oil only injections). After the supplementation period the research team tested for signs of inflammation and protein deposition in the eyes of both sets of mice.
They reported that for the mice receiving vitamin D3, inflammation was reduced, protein debris partially removed, and tests suggested that vision was improved.
The team said that the changes were also associated with a significantly reduced activated macrophages numbers and inflammation in the retina.
“It is also associated with clearance of amyloid beta deposition and improved retinal function,” noted Jeffery and his colleagues. They said that inflammation and the accumulation of amyloid beta are known to contribute, to an increased risk of AMD.
“When we gave older mice the vitamin D we found that deposits of amyloid beta were reduced in their eyes and the mice showed an associated improvement of vision,” reiterated Jeffery.
The UCL professor noted that amyloid beta deposits have also been linked to Alzheimer's disease, where new evidence has suggested that the sunshine vitamin could have a role in reducing its build up in the brain.
“When we saw this effect in the eyes as well, we immediately wondered where else these deposits might be being reduced," said Jeffery – who explained that his team then went on to study the blood vessels of the mice.
They found that mice given the vitamin D supplement also had significantly less amyloid beta build up in their blood vessels – including in the aorta.
"Finding that amyloid deposits were reduced in the blood vessels of mice that had been given vitamin D supplements suggests that vitamin D could be useful in helping to prevent a range of age-related health problems, from deteriorating vision to heart disease," commented Jeffery.
Source: Neurobiology of Aging
Published online ahead of print, doi: 10.1016/j.neurobiolaging.2011.12.002,
“Vitamin D rejuvenates aging eyes by reducing inflammation, clearing amyloid beta and improving visual function”
Authors: V. Lee, E. Rekhi, J.H. Kam, G. Jeffery