Vitamin, fatty acid may help chop risk of eye disease, studies suggest
Eating fish rich in omega-3 fatty acids and taking vitamin D may help the reduce the risk for age-related macular degeneration, the most common cause of irreversible vision loss in older people in the developed world, studies suggest.
Age-related macular degeneration, or AMD, is the leading cause of blindness among Canadians over the age of 50, and affects about 15 million people in North America. AMD occurs when the macula, the area at the back of the retina that produces the sharpest vision, deteriorates over time.
There is currently no way to prevent AMD but in the May issue of the Archives of Ophthalmology, two U.S. teams of researchers looked at potential nutrient-based strategies.
Researchers in the first study found that people who were least likely to have the diseaseate more than two medium (113-gram) servings of fishper week — or more than one serving, if the fish wasbroiled or baked.
The studytracked AMD among 4,519 people in the United States aged 60 to 80 who were enrolled in 1992 through 1998.
Participants had photographs taken of their retinas to determine the extent of disease, if any, and they filled in questionnaires on how often they ate foods rich in certain vitamins, minerals and other nutrients such as omega-3 fatty acids found in fatty fish such as tuna and salmon.
The researchers then comparedthe 1,115 participants who did not have symptoms of the disease when the study started were compared with 658 people with the severe neovascular form of AMD.
"These results and those from other observational analytic investigations suggest that modifying diet to include more foods rich in omega-3 long-chain polyunsaturated fatty acids could result in a reduction in the risk of having neovascular AMD," the study's authors concluded.
Omega-3 fatty acids may affect the development of nerve-related diseases of the retina, the researchers said.
For example, they said, one type of omega-3 called docosahexaenoic acid or DHA may protect the retina by influencing which genes get turned on and off. They saidfatty acids in general may promote cell survival, proper function in blood vessels, reduce inflammation and help maintain energy balance.
'Vitamin D may protect against AMD'
The second study found that people who had the most vitamin D in their blood were 40 per cent less likelyto haveearly AMD than those with the least amount of the vitamin.
A higher intake ofmilk, which is fortified with vitamin D, was linked to a lower risk of early AMD, while fish intake was tied to a lower risk of advanced disease, the researchers found.
"The study provides evidence that vitamin D may protect against AMD," wrote the team, led byNiyati Parekh, of the University of Medicine and Dentistry of New Jersey.
Parekh andcolleagues analyzed data from 7,752 people who were enrolled between 1988 and 1994.
Participants had physicals that included taking blood and urine samples, photographs of the retinas, and interviews and questionnaires about diet and lifestyle.
The study's authors speculated that vitamin D may reduce the risk by reducing inflammation or by preventing the growth of new blood vessels in the retina that contribute to some forms of AMD.
However, they said thereis not enough evidence on the relationship between vitamin D and AMD to make recommendations on the best levels of the vitamin in the blood, or the amount of milk or fish that people should eat toprotect against AMD or its progression.