Age-related macular degeneration: vitamin D deficiency and genetics to blame

In women, age-related macular degeneration, an eye disease associated with advancing age, affects those with vitamin D deficiency more, and this risk increases even more in those genetically predisposed due to particular gene variants.

This was revealed in a study published in the journal JAMA Ophtalmology by a team of researchers from the University at Buffalo (USA).

What is age-related macular degeneration?

Age-related macular degeneration (AMD) is a disease of the eye and is related to the impairment of the macula; the central area of the retina. This deterioration can cause a drastic reduction in the visual field. The disease is the main cause of progressive decrease and loss of vision in the elderly in industrialized countries; an estimated 63,000 new cases of MSD occur in Italy each year. The causes of this disease are diverse and represent a combination of genetic and environmental factors that contribute to the 'aging of the macula. One of the factors most involved in the onset of MSD appears to be oxidative damage caused by so-called free radicals, molecules that are particularly harmful and aggressive to the body. In this regard, certain substances such as antioxidant vitamins A, C and E and carotenoids are able to protect the retina against age-related oxidative damage. So, too, do omega-3s, the polyunsaturated fatty acids essential for maintaining the structural and functional functions of the retina, appear to counteract the disease.

Vitamin D and two genes also influence the onset of the disease

In the past few years, three large studies, named AREDS and AREDS2 and CAREDS, have shown that increasing the consumption of antioxidant nutrients such as vitamins C and E, zinc, copper, beta-carotene, and lutein and zeaxanthin-two molecules belonging to the carotenoid family and key components of the macula-can significantly reduce the progression of AMD. Recently, it has been hypothesized how vitamin D deficiency may also increase the likelihood of ocular disease onset. The purpose of this new study was precisely to confirm and examine the association with vitamin D and the possible influence of genetic factors in this relationship. The study involved a group of 913 women who had participated in the CAREDS study. Between 10% and 30% of the participants showed vitamin D deficiency (concentrations below 30 nmol/L) or suboptimal level (concentrations between 20 and 50 nmol/L) . 

Specifically, the researchers examined in each subject the relationship between serum vitamin D levels, two different forms of the CFH gene believed to be predisposing for AMD, and the risk of being affected by age-related macular degeneration. The CFH gene is responsible for the production of the protein of the same name; this is involved in the immune response that is triggered when the disease arises Statistical analyses showed that in women with deficient or suboptimal concentrations increased the likelihood of AMD occurrence by 2.6 and 1.5 times, respectively, and that among them the risk was greatest in those with a high-risk form of the CFH gene. Women with vitamin D deficiency and both allelic forms of GFH risk manifested a 6.7-fold increased likelihood of being affected by AMD compared with those not genetically predisposed.

Study supports a role for vitamin D in eye health 

According to the researchers who carried out the study, these results not only confirm that low blood concentrations of antioxidant nutrients predispose to the onset of MSD, and that, in the case in vitamin D, gene forms may also influence the risk of onset.

Source: Millen AE, Meyers KJ, Liu Z, Engelman CD, Wallace RB, LeBlanc ES, Tinker LF, Lyengar SK, Robinson JG, Sarto GE, Mares JA. Association between vitamin D status and age-related macular degeneration by genetic risk. 2015 JAMA Opthalmol doi: 10.1001/jamaopthalmol.2015.2715