High homocysteine, low folate and B12 predict macular degeneration
Tuesday, May 14, 2013. An article published ahead of print on May 1, 2013 in the American Journal of Clinical Nutrition reports the finding of Australian researchers of a protective effect for higher serum levels of vitamin B12 and folate against the risk of developing age-related macular degeneration (AMD) in men and women aged 55 and older. The study also revealed a greater risk of AMD in association with higher serum levels of homocysteine, which is a risk factor for heart disease and peripheral vascular disease.
Paul Mitchell of the University of Sydney and his colleagues analyzed data from 1,390 participants in the Blue Mountains Eye Study of common eye diseases in residents aged 49 and older of a suburban Australian area. Eye examinations were conducted upon enrollment and at five, ten and fifteen years. Serum homocysteine, folate and vitamin B12 levels were measured and food frequency questionnaires were completed at the five year follow-up visit.
From the five-year through the fifteen year follow-up visit, 219 subjects were diagnosed with AMD. The risk of the disease increased in association with rising homocysteine levels. In comparison with those with lower homocysteine levels, participants whose levels were greater than 15 micromoles per liter had a 53 percent greater risk of AMD.
Among those with deficient folate levels, the risk of AMD was 89% higher in comparison with the risk experienced by subjects with greater levels. Vitamin B12 deficiency also increased risk. Participants whose vitamin B12 levels were less than 185 picomoles per liter had a 58 percent greater risk of early AMD and more than double the risk of late AMD than those whose levels were higher.
Increasing intake of vitamin B12 from diet and supplements was associated with a declining risk of AMD, and high dietary folate was associated with a significant reduction in the risk of late stage disease. In a separate analysis of vitamin B12 from supplements only, the risk of early, late and any AMD was reduced, with those who reported using the supplements having a 63% lower risk of late disease in comparison with nonusers.
"Elevated serum total homocysteine and folate and vitamin B12 deficiencies predicted increased risk of incident AMD, which suggests a potential role for vitamin B12 and folate in reducing AMD risk," the authors write. "If our findings are confirmed, efforts at the prevention of elevated serum total homocysteine either by treatment with folic acid and vitamin B12 supplements or a simple strategy of eating a healthful diet by incorporating a range of foods that contain folate such as leafy green vegetables and fortified foods could potentially contribute to reducing the burden of blindness from age-related macular degeneration."