Age-related macular degeneration (AMD), a common, progressive eye disease in older people, is the leading cause of irreversible visual impairment and blindness for people over the age of 50 in the Western world, affecting approximately 25-30 million people.
Individuals with early or intermediate stages of the disease, thought to number more than 8 million people in the US alone, make up a growing segment of the elderly population, writes Dr Johanna M. Seddon, of the Massachusetts Eye and Ear Infirmary in Boston, and colleagues in this month's issue of the Archives of Ophthalmology (121:1728-1737).
The team set out to identify dietary factors that could reduce the risk of AMD worsening in at-risk populations. They studied 261 patients aged 60 or older who had some sign of AMD in at least one eye. Participants were followed for an average of 4.6 years and completed food frequency questionnaires designed to measure the amounts and kinds of foods eaten in the previous week.
"In this prospective longitudinal study, we found that higher levels of dietary fat intake were associated with the progression of AMD to the advanced stages associated with visual loss," the authors write.
"Specifically, higher intake of vegetable fat, and to a lesser extent animal fat, increased rates of progression. Saturated, monounsaturated, polyunsaturated and transunsaturated fats were also related to progression," they added.
Food groups with higher levels of these fats, particularly processed baked goods, were also associated with a higher rate of progression of AMD, increasing the risk by about two-fold. Nuts were the exception with protective effects on eye health, reported the scientists.
"Thus, dietary intake of fat, including specific types of fat as well as fat-containing foods, is a potentially important behaviour that can modify the outcome for patients who already have the early or intermediate forms of AMD," write the researchers.
Research has also linked low levels of lutein and zeaxanthin - carotenoids found in dark green, leafy vegetables such as spinach and kale - to risk of age-related macular degeneration. Lutein supplements and other antioxidants such as zinc are becoming increasingly popular for eye health as consumers become more aware of dietary prevention of the disease.